Criminal Investigation Question

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ISBN 978-1-29204-145-2

Forensic Science From the Crime Scene to the Crime Lab

Richard Saferstein Second Edition

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Pearson New International Edition

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Forensic Science From the Crime Scene to the Crime Lab

Richard Saferstein Second Edition

Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England and Associated Companies throughout the world

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ISBN 10: 1-292-04145-5 ISBN 13: 978-1-292-04145-2

ISBN 10: 1-292-04145-5 ISBN 13: 978-1-292-04145-2

Table of Contents

P E A R S O N C U S T O M L I B R A R Y

I

1. Introduction

1

1Richard Saferstein

2. Securing and Searching the Crime Scene

33

33Richard Saferstein

3. Recording the Crime Scene

51

51Richard Saferstein

4. Collection of Crime-Scene Evidence

83

83Richard Saferstein

5. Physical Evidence

107

107Richard Saferstein

6. Death Investigation

125

125Richard Saferstein

7. Crime-Scene Reconstruction

155

155Richard Saferstein

8. Fingerprints

167

167Richard Saferstein

9. Firearms, Toomarks, and Other Impressions

195

195Richard Saferstein

10. Bloodstain Pattern Analysis

235

235Richard Saferstein

11. Computer Forensics

257

257Richard Saferstein

12. Drugs

291

291Richard Saferstein

13. Forensic Toxicology

331

331Richard Saferstein

II

14. Trace Evidence I: Hairs and Fibers

361

361Richard Saferstein

15. Trace Evidence II: Paint, Glass, and Soil

387

387Richard Saferstein

16. Biological Stain Analysis: DNA

415

415Richard Saferstein

17. Forensic Aspects of Fire and Explosion Investigation

457

457Richard Saferstein

18. Document Examination

487

487Richard Saferstein

19. Appendix: Guides to the Collection of Physical Evidence–FBI

511

511Richard Saferstein

20. Appendix: Instructions for Collecting Gunshot Residue (GSR)

529

529Richard Saferstein

21. Appendix: Chemical Formulas for Latent Fingerprint Development

533

533Richard Saferstein

22. Appendix: Chemical Formulas for Development of Footwear Impressions in Blood

539

539Richard Saferstein

543

543Index

CASEY ANTHONY: THE CSI EFFECT? Few criminal proceedings have captured the attention of the American public or have invoked stronger emotions than the Casey Anthony murder trial. How could a defen- dant who failed to report her two-year-old child missing for 31 days walk away scot-free from a murder conviction?

This case had all the makings of a strong circumstantial case for the state.

The state’s theory was that Casey used chloroform to render her daughter un- conscious, placed duct tape over Caylee’s mouth and nose, and kept the body in the trunk for several days before disposing of it. Caylee’s decomposed remains were discovered more than fi ve months after she was reported missing.

Have TV forensic dramas created an environment in the courtroom that neces- sitates the existence of physical evidence to directly link a defendant to a crime scene? The closest the state came to a direct link was a hair found in the trunk of Casey’s car. However, the DNA test on the hair could only link the hair to Caylee’s maternal relatives: Casey, Casey’s mother (Caylee’s maternal grandmother), and

Casey’s brother (Caylee’s uncle). And Caylee herself. No unique characteristics were found to link the duct tape on the body with that found in the Anthony home.

No DNA, no fi ngerprints, no conviction.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Defi ne forensic science and list the major disciplines forensic

science encompasses. • Recognize the major contributors to the development of

forensic science. • Account for the rapid growth of forensic laboratories in the

past forty years. • Describe the services of a typical comprehensive crime

laboratory in the criminal justice system. • Compare and contrast the Frye and Daubert decisions relating

to the admissibility of scientifi c evidence in the courtroom. • Explain the role and responsibilities of the expert witness. • List the specialized forensic services, aside from the crime

laboratory, that are generally available to law enforcement personnel.

Introduction

Joe Burbank/MCT/Newscom

From Chapter 1 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

INTRODUCTION

Defi nition and Scope of Forensic Science Forensic science, in its broadest defi nition, is the application of science to law. As our society has grown more complex, it has become more dependent on rules of law to regulate the activities of its members. Forensic science applies the knowledge and technology of science to the defi nition and enforcement of such laws.

Each year, as government fi nds it increasingly necessary to regulate the activities that most intimately infl uence our daily lives, science merges more closely with civil and criminal law. Consider, for example, the laws and agen- cies that regulate the quality of our food, the nature and potency of drugs, the extent of automobile emissions, the kind of fuel oil we burn, the purity of our drinking water, and the pesticides we use on our crops and plants. It would be diffi cult to conceive of a food or drug regulation or environmental protection act that could be effectively monitored and enforced without the assistance of scientifi c technology and the skill of the scientifi c community.

Laws are continually being broadened and revised to counter the alarm- ing increase in crime rates. In response to public concern, law enforcement agencies have expanded their patrol and investigative functions, hoping to stem the rising tide of crime. At the same time, they are looking more to the scientifi c community for advice and technical support for their efforts. Can the technology that put astronauts on the moon, split the atom, and eradicated most dreaded diseases be enlisted in this critical battle?

Unfortunately, science cannot offer fi nal and authoritative solutions to problems that stem from a maze of social and psychological factors. However, as the content of this text attests, science occupies an important and unique role in the criminal justice system—a role that relates to the scientist’s ability to supply accurate and objective information about the events that have oc- curred at a crime scene. A good deal of work remains to be done if the full potential of science as applied to criminal investigations is to be realized.

Because of the vast array of civil and criminal laws that regulate society, forensic science, in its broadest sense, has become so comprehensive a sub- ject that a meaningful introductory textbook treating its role and techniques would diffi cult to create and probably overwhelming to read. For this reason, we have narrowed the scope of the subject according to the most common defi nition: Forensic science is the application of science to the criminal and civil laws that are enforced by police agencies in a criminal justice system. Forensic science is an umbrella term encompassing a myriad of pro- fessions that use their skills to aid law enforcement offi cials in conducting their investigations.

The diversity of professions practicing forensic science is illustrated by the eleven sections of the American Academy of Forensic Science, the largest forensic science organization in the world:

1. Criminalistics 2. Digital and Multimedia Sciences 3. Engineering Science 4. General 5. Jurisprudence 6. Odontology 7. Pathology/Biology 8. Physical Anthropology 9. Psychiatry/ Behavioral Science 10. Questioned Documents 11. Toxicology

2

INTRODUCTION

Even this list of professions is not exclusive. It does not encompass skills such as fi ngerprint examination, fi rearm and tool mark examination, computer and digital data analysis, and photography.

Obviously, to author a book covering all of the major activities of forensic science as they apply to the enforcement of criminal and civil laws by police agencies would be a major undertaking. Thus, this text will further restrict itself to discussions of the subjects of chemistry, biology, physics, geology, and com- puter technology, which are useful for determining the evidential value of crime- scene and related evidence. Forensic pathology, psychology, anthropology, and odontology also encompass important and relevant areas of knowledge and practice in law enforcement, each being an integral part of the total forensic sci- ence service that is provided to any up-to-date criminal justice system. However, these subjects go beyond the intended scope of this text, and except for brief discussions, along with pointing the reader to relevent websites, the reader is referred elsewhere for discussions of their applications and techniques. 1 Instead, this article focuses on the services of what has popularly become known as the crime laboratory, where the principles and techniques of the physical and natu- ral sciences are practiced and applied to the analysis of crime-scene evidence.

For many, the term criminalistics seems more descriptive than forensic sci- ence for describing the services of a crime laboratory. Regardless of his or her title—criminalist or forensic scientist—the trend of events has made the scien- tist in the crime laboratory an active participant in the criminal justice system.

Prime-time television shows like CSI: Crime Scene Investigation have greatly increased the public’s awareness of the use of science in criminal and civil investigations (see Figure 1 ). However, by simplifying scientifi c proce- dures to fi t the allotted airtime, these shows have created within both the public and the legal community unrealistic expectations of forensic science. In these shows, members of the CSI team collect evidence at the crime scene, process all evidence, question witnesses, interrogate suspects, carry out search war- rants, and testify in court. In the real world, these tasks are almost always

FIGURE 1 A scene from CSI , a forensic science television show. SUN/Newscom

3

INTRODUCTION

delegated to different people in different parts of the criminal justice system. Procedures that in reality could take days, weeks, months, or years appear on these shows to take mere minutes. This false image is signifi cantly responsible for the public’s high interest in and expectations for DNA evidence.

The dramatization of forensic science on television has led the public to believe that every crime scene will yield forensic evidence, and it produces unrealistic expectations that a prosecutor’s case should always be bolstered and supported by forensic evidence. This phenomenon is known as the “CSI effect.” Some jurists have come to believe that this phenomenon ultimately detracts from the search for truth and justice in the courtroom.

History and Development of Forensic Science Forensic science owes its origins, fi rst, to the individuals who developed the principles and techniques needed to identify or compare physical evidence and, second, to those who recognized the need to merge these principles into a coherent discipline that could be practically applied to a criminal justice system.

The roots of forensic science reach back many centuries, and history records a number of instances in which individuals closely observed evidence and applied basic scientifi c principles to solve crimes. Not until relatively recently, however, did forensic science take on the more careful and systematic approach that characterizes the modern discipline.

EARLY DEVELOPMENTS

One of the earliest records of applying forensics to solve criminal cases comes from third-century China. A manuscript titled Yi Yu Ji (“A Collection of Crimi- nal Cases”) reports how a coroner solved a case in which a woman was sus- pected of murdering her husband and burning the body, claiming that he died in an accidental fi re. Noticing that the husband’s corpse had no ashes in its mouth, the coroner performed an experiment to test the woman’s story. He burned two pigs—one alive and one dead—and then checked for ashes in- side the mouth of each. He found ashes in the mouth of the pig that was alive before it was burned, but none in the mouth of the pig that was dead before- hand. The coroner thus concluded that the husband, too, was dead before his body was burned. Confronted with this evidence, the woman admitted her guilt. The Chinese were also among the fi rst to recognize the potential of fi n- gerprints as a means of identifi cation.

Although cases such as that of the Chinese coroner are noteworthy, this kind of scientifi c approach to criminal investigation was for many years the exception rather than the rule. Limited knowledge of anatomy and pathology hampered the development of forensic science until the late seventeenth and early eighteenth centuries. For example, the fi rst recorded notes about fi ngerprint characteris- tics were prepared in 1686 by Marcello Malpighi, a professor of anatomy at the University of Bologna in Italy. Malpighi, however, did not acknowledge the value of fi ngerprints as a method of identifi cation. The fi rst scientifi c paper about the nature of fi ngerprints did not appear until more than a century later, but it also did not recognize their potential as a form of identifi cation.

INITIAL SCIENTIFIC ADVANCES

As physicians gained a greater understanding of the workings of the body, the fi rst scientifi c treatises on forensic science began to appear, such as the 1798 work “A Treatise on Forensic Medicine and Public Health” by the French physician

4

INTRODUCTION

François-Emanuel Fodéré. Breakthroughs in chemis- try at this time also helped forensic science take sig- nifi cant strides forward. In 1775, the Swedish chemist Carl Wilhelm Scheele devised the fi rst successful test for detecting the poison arsenic in corpses. By 1806, the German chemist Valentin Ross had discovered a more precise method for detecting small amounts of arsenic in the walls of a victim’s stomach. The most signifi cant early fi gure in this area was Mathieu Orfi la, a Spaniard who is considered the father of forensic toxicology. In 1814, Orfi la published the fi rst scientifi c treatise on the detection of poisons and their effects on animals. This treatise established forensic toxicology as a legitimate scientifi c endeavor (see Figure 2 ).

The mid-1800s saw a spate of advances in sev- eral scientifi c disciplines that furthered the fi eld of forensic science. In 1828, William Nichol invented the polarizing microscope. Eleven years later, Henri- Louis Bayard formulated the fi rst procedures for mi- croscopic detection of sperm. Other developments during this time included the fi rst microcrystalline test for hemoglobin (1853) and the fi rst presumptive test for blood (1863). Such tests soon found practi- cal applications in criminal trials. Toxicological evi- dence at trial was fi rst used in 1839, when a Scottish chemist named James Marsh testifi ed that he had detected arsenic in a victim’s body. During the 1850s and 1860s, the new science of photography was also used in forensics to record images of prisoners and crime scenes.

LATE-NINETEENTH-CENTURY PROGRESS

By the late nineteenth century, public offi cials were beginning to apply knowl- edge from virtually all scientifi c disciplines to the study of crime. Anthropology and morphology (the study of the structure of living organisms) were applied to the fi rst system of personal identifi cation, devised by the French scientist Alphonse Bertillon in 1879. Bertillon’s system, which he dubbed anthropome- try, was a procedure that involved taking a series of bodily measurements as a means of distinguishing one individual from another. For nearly two decades, this system was considered the most accurate method of personal identifi ca- tion. Bertillon’s early efforts earned him the distinction of being known as the father of criminal identifi cation (see Figure 3 ).

Bertillon’s anthropometry, however, would soon be supplanted by a more reliable method of identifi cation: fi ngerprinting. Two years before the publica- tion of Bertillon’s system, the US microscopist Thomas Taylor had suggested that fi ngerprints could be used as a means of identifi cation, but his ideas were not immediately followed up. Three years later, the Scottish physician Henry Faulds made a similar assertion in a paper published in the journal Nature . However, it was the Englishman Francis Henry Galton who undertook the fi rst defi nitive study of fi ngerprints and developed a methodology of classify- ing them for fi ling. In 1892, Galton published a book titled Finger Prints, which contained the fi rst statistical proof supporting the uniqueness of fi ngerprints and the effectiveness of his method. His book went on to describe the basic principles that would form our present system of identifi cation by fi ngerprints.

The fi rst treatise describing the application of scientifi c disciplines to the fi eld of criminal investigation was written by Hans Gross in 1893. Gross, a public prosecutor and judge in Graz, Austria, spent many years studying and

FIGURE 2 Mathieu Orfi la. The Granga Collection, New York

5

INTRODUCTION

FIGURE 3 Bertillon’s system of bodily measurements used for the identifi cation of an individual. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

6

INTRODUCTION

developing principles of criminal investigation. In his classic book Handbuch für Untersuchungsrichter als System der Kriminalistik (later published in Eng- lish under the title Criminal Investigation ), he detailed the assistance that investigators could expect from the fi elds of microscopy, chemistry, physics, miner- alogy, zoology, botany, anthropometry, and fi nger- printing. He later introduced the forensic journal Archiv für Kriminal Anthropologie und Kriminalistik, which still reports improved methods of scientifi c crime detection.

Ironically, the best-known fi gure in nineteenth- century forensics is not a real person but a fi c- tional character: the legendary detective Sherlock Holmes (see Figure 4) . Many people today believe that Holmes’s creator, Sir Arthur Conan Doyle, had a considerable infl uence on popularizing scientifi c crime-detection methods. In adventures with his partner and biographer, Dr. John Watson, Holmes was the fi rst to apply the newly developing prin- ciples of serology (the study of blood and bodily fl uids), fi ngerprinting, fi rearms identifi cation, and questioned-document examination long before their value was recognized and accepted by real-life criminal investigators. Holmes’s feats excited the imagination of an emerging generation of forensic scientists and criminal investigators. Even in the fi rst Sherlock Holmes novel, A Study in Scarlet, pub- lished in 1887, we fi nd examples of Doyle’s uncanny ability to describe scientifi c methods of detection years before they were ac- tually discovered and implemented. For instance, here Holmes explains the potential usefulness of forensic serology to criminal investigation:

“I’ve found it. I’ve found it,” he shouted to my companion, running toward us with a test tube in his hand. “I have found a reagent which is precipitated by hemo- globin and by nothing else . . . . Why, man, it is the most practical medico-legal discovery for years. Don’t you see that it gives us an infallible test for blood stains? . . . The old guaiacum test was very clumsy and uncertain. So is the microscopic ex- amination for blood corpuscles. The latter is valueless if the stains are a few hours old. Now, this appears to act as well whether the blood is old or new. Had this test been invented, there are hundreds of men now walking the earth who would long ago have paid the penalty of their crimes . . . . Criminal cases are continually hing- ing upon that one point. A man is suspected of a crime months perhaps after it has been committed. His linen or clothes are examined and brownish stains discovered upon them. Are they blood stains, or rust stains, or fruit stains, or what are they? That is a question which has puzzled many an expert, and why? Because there was no reliable test. Now we have the Sherlock Holmes test, and there will no longer be any diffi culty.”

TWENTIETH-CENTURY BREAKTHROUGHS

The pace of technological change quickened considerably in the twentieth cen- tury, and with it the rate of advancements in forensic science. In 1901, Dr. Karl Landsteiner discovered that blood can be grouped into different categories, now recognized as the blood types A, B, AB, and O. The possibility that blood grouping could be useful in identifying an individual intrigued Dr. Leone Lattes,

FIGURE 4 Sir Arthur Conan Doyle’s legendary detective Sherlock Holmes applied many of the principles of modern forensic science long before they were adopted widely by real-life police. © Paul C. Chauncey/CORBIS. All rights reserved.

7

INTRODUCTION

a professor at the Institute of Forensic Medicine at the University of Turin in Italy. In 1915, Lattes devised a relatively simple procedure for determining the blood group of the dried blood in a bloodstain, a technique that he immediately applied to criminal investigations.

At around the same time, Albert S. Osborn was conducting pioneering work in document examination. In 1910, Osborn wrote the fi rst signifi cant text in this fi eld, Questioned Documents. This book is still a primary reference for document examiners. Osborn’s development of fundamental principles of document examination was responsible for the acceptance of documents as scientifi c evidence by the courts.

One of the most important contributors to the fi eld in the early twentieth century was the Frenchman Edmond Locard. Although Hans Gross was a pioneering advocate for the use of the scientifi c method in criminal investi- gations, Locard fi rst demonstrated how the principles enunciated by Gross could be incorporated within a workable crime laboratory. Locard’s formal education was in both medicine and law. In 1910, he persuaded the Lyons police department to give him two attic rooms and two assistants to start a police laboratory. During Locard’s fi rst years of work, the instruments avail- able to him were a microscope and a rudimentary spectrometer. However, his enthusiasm quickly overcame the technical and budgetary defi ciencies he encountered, and from these modest beginnings, Locard conducted research and made discoveries that became known throughout the world by foren- sic scientists and criminal investigators. Eventually he became the founder and director of the Institute of Criminalistics at the University of Lyons, which quickly developed into a leading international center for study and research in forensic science (see Figure 5 ).

Locard asserted that when two objects come into contact with each other a cross-transfer of materials occurs ( Locard’s exchange principle ). He strongly believed that every criminal can be connected to a crime by dust particles car- ried from the crime scene. This concept was reinforced by a series of success- ful and well-publicized investigations. In one case, presented with counterfeit coins and the names of three suspects, Locard urged the police to bring the suspects’ clothing to his laboratory. On careful examination, he located small metallic particles in all the garments. Chemical analysis revealed that the par- ticles and coins were composed of exactly the same metallic elements. Con- fronted with this evidence, the suspects were arrested and soon confessed to the crime. After World War I, Locard’s successes inspired the formation of police laboratories in Vienna, Berlin, Sweden, Finland, and Holland.

The microscope came into widespread use in forensic science during the twentieth century, and its applications grew dramatically. Perhaps the leading fi gure in the fi eld of microscopy was Dr. Walter C. McCrone. During his lifetime, McCrone became the world’s preeminent microscopist. Through his books, journal publications, and research institute, he was a tireless advocate for ap- plying microscopy to analytical problems, particularly forensic science cases. McCrone’s exceptional communication skills made him a much-sought-after in- structor, and he educated thousands of forensic scientists throughout the world in the application of microscopic techniques. Dr. McCrone used microscopy, of- ten in conjunction with other analytical methodologies, to examine evidence in thousands of criminal and civil cases throughout his long and illustrious career.

Another trailblazer in forensic applications of microscopy was U.S. Army Colonel Calvin Goddard, who refi ned the techniques of fi rearms examination by using the comparison microscope. Goddard’s work allows investigators to determine whether a particular gun has fi red a bullet by comparing the bullet with another that is test-fi red from the suspect’s weapon. His expertise estab- lished the comparison microscope as the indispensable tool of the modern fi rearms examiner.

Locard’s exchange principle Whenever two objects come into contact with one another, materials are exchanged between them.

8

INTRODUCTION

MODERN SCIENTIFIC ADVANCES

Since the mid-twentieth century, a revolution in computer technology has made possible a quantum leap forward in human knowledge. The resulting explosion of scientifi c advances has had a dramatic impact on the fi eld of forensic science by introducing a wide array of sophisticated techniques for analyzing evidence related to a crime. Procedures such as chromatography, spectrophotometry, and electrophoresis (all discussed in later chapters) allow the modern forensic scientist to determine with astounding accuracy the identity of a substance and to connect even tiny fragments of evidence to a particular person and place.

Undoubtedly the most signifi cant modern advance in forensic science has been the discovery and refi nement of DNA typing in the late twentieth and early twenty-fi rst centuries. Sir Alec Jeffreys developed the fi rst DNA profi ling test in 1984, and two years later he applied it for the fi rst time to solve a crime, identify- ing Colin Pitchfork as the murderer of two young English girls. The same case also marked the fi rst time DNA profi ling established the innocence of a criminal suspect. Made possible by scientifi c breakthroughs in the 1950s and 1960s, DNA typing offers law enforcement offi cials a powerful tool for establishing the pre- cise identity of a suspect, even when only a small amount of physical evidence is available. Combined with the modern analytical tools mentioned earlier, DNA typing has revolutionized the practice of forensic science (see Figure 6 ).

Another signifi cant recent development in forensics is the establishment of computerized databases to store information on physical evidence such as

FIGURE 5 Edmond Locard. Collection of Roger-Viollet, The Image Works

9

INTRODUCTION

fi ngerprints, markings on bullets and shell casings, and DNA. These databases have proved to be invaluable, enabling law enforcement offi cials to compare evidence found at crime scenes to thousands of pieces of similar information. This has signifi cantly reduced the time required to analyze evidence and in- creased the accuracy of the work done by police and forensic investigators.

Although this brief narrative is by no means a complete summary of his- torical advances in forensics, it provides an idea of the progress that has been made in the fi eld by dedicated scientists and law enforcement personnel. Even Sherlock Holmes probably couldn’t have imagined the extent to which science is applied in the service of criminal investigation today.

Quick Review • Forensic science is the application of science to criminal and civil laws that

are enforced by police agencies in a criminal justice system. • The fi rst system of personal identifi cation was called anthropometry. It

distinguished one individual from another based on a series of bodily measurements.

• Forensic science owes its origins to individuals such as Bertillon, Galton, Lattes, Goddard, Osborn, and Locard, who developed the principles and techniques needed to identify and compare physical evidence.

• Locard’s exchange principle states that, when two objects come into con- tact with each other, a cross-transfer of materials occurs that can connect a criminal suspect to his or her victim.

Crime Laboratories The steady advance of forensic science technologies during the twentieth century led to the establishment of the fi rst facilities specifi cally dedicated to forensic analysis of criminal evidence. These crime laboratories are now the centers for both forensic investigation of ongoing criminal cases and research into new techniques and procedures to aid investigators in the future.

FIGURE 6 Sir Alec Jeffreys. Homer Sykes/Alamy Images Royalty Free

10

INTRODUCTION

HISTORY OF CRIME LABS

IN THE UNITED STATES

The oldest forensic laboratory in the United States is that of the Los Angeles Police Department, created in 1923 by August Vollmer, a police chief from Berkeley, California. In the 1930s, Vollmer headed the fi rst U.S. university institute for criminology and criminalistics at the University of California at Berkeley. However, this institute lacked any offi cial status in the university until 1948, when a school of criminology was formed. The famous criminalist Paul Kirk was selected to head the school’s criminalistics department. Many graduates of this school have gone on to develop forensic laboratories in other parts of the state and country.

In 1932, the Federal Bureau of Investigation (FBI), under the director- ship of J. Edgar Hoover, organized a national laboratory that offered forensic services to all law enforcement agencies in the country. During its formative stages, Hoover consulted extensively with business executives, manufactur- ers, and scientists, whose knowledge and experience guided the new facility through its infancy. The FBI Laboratory is now the world’s largest forensic laboratory, performing more than one million examinations every year (see Figure 7 ). Its accomplishments have earned it worldwide recognition, and its structure and organization have served as a model for forensic laboratories formed at the state and local levels in the United States as well as in other countries. Furthermore, the opening of the FBI’s Forensic Science Research and Training Center in 1981 gave the United States, for the fi rst time, a facility dedicated to conducting research toward new and reliable scientifi c methods that can be applied to forensic science. This facility is also used to train crime laboratory personnel in the latest forensic science techniques and methods.

Despite the existence of the FBI Laboratory, the United States has no na- tional system of forensic laboratories. Instead, many local law enforcement jurisdictions—city, county, and state—each operate their own independent crime labs. California, for example, has numerous federal, state, county, and city crime laboratories, many of which operate independently. However, in 1972 the California Department of Justice created a network of integrated state-operated crime laboratories consisting of regional and satellite facilities. An informal exchange of information and expertise occurs within California’s criminalist community through a regional professional society, the California Association of Criminalists. This organization is the forerunner of a number of regional organizations that have developed throughout the United States to foster cooperation among the nation’s growing community of criminalists.

FIGURE 7 (a) Exterior and (b) interior views of the FBI crime laboratory in Quantico, Virginia. Charles Dharapak/AP Wide World Photos

11

INTRODUCTION

ORGANIZATION OF A CRIME LABORATORY

The development of crime laboratories in the United States has been char- acterized by rapid growth accompanied by an unfortunate lack of national and regional planning and coordination. Approximately four hundred pub- lic crime laboratories operate at various levels of government—federal, state, county, and municipal. The size and diversity of crime laboratories make it impossible to select any one model that best describes a typical crime labora- tory. Although most of these facilities function as part of a police department, others operate under the direction of the prosecutor’s or district attorney’s offi ce, and some work with the laboratories of the medical examiner or coro- ner. Far fewer are affi liated with universities or exist as independent agencies in government. Laboratory staff sizes range from one person to more than one hundred, and services offered may be quite diverse or very specialized, depending on the responsibilities of the agency that houses the laboratory.

THE GROWTH OF CRIME LABORATORIES

Most existing crime laboratories have been organized by agencies that either foresaw their potential application to criminal investigations or were pressed by the increasing demands of casework. Several reasons explain the unparal- leled growth of crime laboratories during the past forty years: Supreme Court decisions in the 1960s compelled police to place greater emphasis on securing scientifi cally evaluated evidence. The requirement to advise criminal suspects of their constitutional rights and their right of immediate access to counsel has all but eliminated confessions as a routine investigative tool; successful prosecution of criminal cases requires a thorough and professional police investigation, frequently incorporating the skills of forensic science experts. Modern technology has provided forensic scientists with many new skills and techniques to meet the challenges accompanying their increased participation in the criminal justice system.

Coinciding with changing judicial requirements has been the staggering increase in crime rates in the United States over the past forty years. Although it seems that this factor alone could account for the increased use of crime laboratory services by police agencies, only a small percentage of police inves- tigations generate evidence requiring scientifi c examination. There is one im- portant exception, however: drug-related arrests. All illicit-drug seizures must be sent to a forensic laboratory for confi rmatory chemical analysis before the case can be adjudicated. Since the mid-1960s, drug abuse has accelerated to nearly uncontrollable levels and has resulted in crime laboratories being inun- dated with drug specimens.

A more recent contributor to the growth and maturation of crime labora- tories has been the advent of DNA profi ling. Since the early 1990s, this technol- ogy has progressed to the point of individualization or near-individualization of biological evidence. That is, traces of blood, semen stains, hair, and saliva residues left behind on stamps, cups, bite marks, and so on, can be positively linked to a criminal. To meet the demands of DNA technology, crime labs have expanded staff and in many cases modernized their physical plants. The labor- intensive demands and sophisticated requirements of DNA technology have affected the structure of the forensic laboratory as has no other technology in the past fi fty years. Likewise, DNA profi ling has become the dominant factor in the general public’s perception of the workings and capabilities of the mod- ern crime laboratory.

In coming years thousands of forensic scientists will be added to the rolls of both public and private forensic laboratories to process crime-scene evi- dence for DNA and to acquire DNA profi les, as mandated by state laws, from

12

INTRODUCTION

the hundreds of thousands of individuals convicted of crimes. This endeavor has already added many new scientists to the fi eld and will eventually more than double the number of scientists employed by forensic laboratories in the United States. A major problem facing the forensic DNA community is the sub- stantial backlog of unanalyzed DNA samples from crime scenes. The number of unanalyzed casework DNA samples reported by state and national agencies varies from month to month but is estimated at around 100,000. In an attempt to eliminate the backlog of convicted offender or arrestee samples to be ana- lyzed and entered into the Combined DNA Index System (CODIS), the federal government has initiated funding for in-house analysis of samples at the crime laboratory and outsourcing samples to private laboratories for analysis.

Beginning in 2008, California began collecting DNA samples from all peo- ple arrested on suspicion of a felony, not just the eventual convict. The state’s database, with approximately one million DNA profi les, is already the third largest in the world, behind those maintained by the United Kingdom and the FBI. The federal government plans to begin following California’s policy.

CRIME LABORATORIES IN THE UNITED STATES Historically, our federal sys- tem of government, combined with a desire to retain local control, has pro- duced a variety of independent laboratories in the United States, precluding the creation of a national system. Crime laboratories to a large extent mirror the fragmented law enforcement structure that exists on the national, state, and local levels. The federal government has no single law enforcement or investigative agency with unlimited jurisdiction.

Four major federal crime laboratories have been created to help investi- gate and enforce criminal laws that extend beyond the jurisdictional bound- aries of state and local forces. The FBI (Department of Justice) maintains the largest crime laboratory in the world. An ultramodern facility housing the FBI’s forensic science services is located in Quantico, Virginia. Its expertise and technology support its broad investigative powers. The Drug Enforcement Administration laboratories (Department of Justice) analyze drugs seized in violation of federal laws regulating the production, sale, and transportation of drugs. The laboratories of the Bureau of Alcohol, Tobacco, Firearms, and Ex- plosives (Department of Justice) analyze alcoholic beverages and documents relating to alcohol and fi rearm excise-tax enforcement and examine weapons, explosive devices, and related evidence to enforce the Gun Control Act of 1968 and the Organized Crime Control Act of 1970. The U.S. Postal Inspection Ser- vice maintains laboratories concerned with criminal investigations relating to the postal service. Each of these federal facilities offers its expertise to any lo- cal agency that requests assistance in relevant investigative matters.

Most state governments maintain a crime laboratory to service state and local law enforcement agencies that do not have ready access to a labora- tory. Some states, such as Alabama, California, Illinois, Michigan, New Jersey, Texas, Washington, Oregon, Virginia, and Florida, have developed a compre- hensive statewide system of regional or satellite laboratories. These operate under the direction of a central facility and provide forensic services to most areas of the state. Having a regional laboratory that operates as part of a state- wide system has increased the accessibility of many local law enforcement agencies to a crime laboratory, while minimizing duplication of services and ensuring maximum interlaboratory cooperation through the sharing of ex- pertise and equipment.

Local laboratories provide services to county and municipal agencies. Generally, these facilities operate independent of the state crime laboratory and are fi nanced directly by local government. However, as costs have risen, some counties have combined resources and created multicounty laboratories to service their jurisdictions. Many of the larger cities in the United States

13

INTRODUCTION

maintain their own crime laboratories, usually under the direction of the local police department. Frequently, a large population and high crime rates com- bine to make a municipal facility, such as that of New York City, the largest crime laboratory in the state.

CRIME LABORATORIES ABROAD Like the United States, most countries in the world have created and now maintain forensic facilities. In contrast to the U.S. system of independent local laboratories, Great Britain has developed a national system of regional laboratories under the direction of the government’s Home Offi ce. England and Wales are serviced by regional laboratories, including the Metropolitan Police Laboratory (established in 1935), which services London. Recently, the British government announced plans to either privatize or sell off its government-operated forensic laboratories. In the early 1990s, the British Home Offi ce reorganized the country’s forensic laboratories into the Forensic Science Service and instituted a system in which police agencies are charged a fee for services rendered by the laboratory. The fees are based on “products,” or a set of examinations that are designed to be suitable for particular types of physical evidence and are packaged together. The fee-for-service concept has encouraged the creation of a number of private laboratories that provide services to both police and criminal defense attorneys. LGC is the largest pri- vately owned provider of forensic science services in the UK. With a staff of over 500, LGC delivers forensic services at eight laboratories in the UK. It is expected that under the planned government reorganization of state forensic laboratories, the bulk of forensic services in England and Wales will be carried out by private laboratories such as LGC.

In Canada, forensic services are provided by three government-funded institutes: (1) Royal Canadian Mounted Police regional laboratories, (2) the Centre of Forensic Sciences in Toronto, and (3) the Institute of Legal Medicine and Police Science in Montreal. Altogether, more than one hundred countries throughout the world have at least one laboratory facility offering forensic science services.

SERVICES OF THE CRIME LABORATORY

Bearing in mind the independent development of crime laboratories in the United States, the wide variation in the services offered to different communi- ties is not surprising. There are many reasons for this, including (1) variations in local laws, (2) the different capabilities and functions of the organization to which a laboratory is attached, and (3) budgetary and staffi ng limitations.

In recent years, many local crime laboratories have been created solely to process drug specimens. Often these facilities were staffed with few person- nel and operated under limited budgets. Although many have expanded their forensic services, some still primarily perform drug analyses. Among crime laboratories providing services beyond drug identifi cation, the diversity and quality of services rendered varies signifi cantly. The following forensic science units might be found in a “full-service” crime laboratory.

BASIC SERVICES PROVIDED BY

FULL-SERVICE CRIME LABORATORIES

PHYSICAL SCIENCE UNIT The physical science unit applies principles and techniques of chemistry, physics, and geology to the identifi cation and com- parison of crime-scene evidence. It is staffed by criminalists who have the expertise to use chemical tests and modern analytical instrumentation to ex- amine items as diverse as drugs, glass, paint, explosives, and soil. In a labora- tory that has a staff large enough to permit specialization, the responsibilities

14

INTRODUCTION

of this unit may be further subdivided into drug identifi cation, soil and mineral analyses, and exami- nation of a variety of trace physical evidence.

BIOLOGY UNIT The biology unit is staffed with biologists and biochemists who identify and per- form DNA profi ling on bloodstains and other dried body fl uids, compare hairs and fi bers, and identify and compare botanical materials such as wood and plants (see Figure 8 ).

FIREARMS UNIT The fi rearms unit examines fi re- arms, discharged bullets, cartridge cases, shotgun shells, and ammunition of all types. Garments and other objects are also examined to detect fi rearm discharge residues and to approximate how far from a target a weapon was fi red. The basic principles of fi rearms examination are also applied to comparing marks made by tools (see Figure 9 ).

DOCUMENT EXAMINATION UNIT The document examination unit studies the handwriting and type- writing on documents in question to ascertain their authenticity and/or source. Related responsibilities include analyzing paper and ink and examining in- dented writings (i.e., the partially visible depressions that appear on the sheet of paper that was under- neath the one that was written on), obliterations, erasures, and burned or charred documents.

PHOTOGRAPHY UNIT A complete photographic laboratory examines and re- cords physical evidence. Its procedures may require the use of highly special- ized photographic techniques, such as digital imaging and infrared, ultraviolet,

FIGURE 9 A forensic analyst examining a fi rearm. mediacolors/Alamy Images

FIGURE 8 A forensic scientist per- forming DNA analysis. Mauro Fermariello/SPL/Photo Researchers, Inc.

15

IntroductIon

# 107652 Cust: Pearson Au: Saferstein Pg. No. 16 Title: Forensic Science Server: PROJECTS

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and X-ray photography, to make invisible information visible to the naked eye. This unit also prepares photographic exhibits for courtroom presentation.

OptiOnal ServiceS prOvided by Full-Service crime labOratOrieS

Toxicology UniT The toxicology group examines body fluids and organs to determine the presence or absence of drugs and poisons. Frequently, such functions are shared with or may be the sole responsibility of a separate labora- tory facility placed under the direction of the medical examiner’s or coroner’s office. In most jurisdictions, field instruments such as the Intoxilyzer are used to determine how much alcohol an individual has consumed. Often the toxicology unit also trains operators of these instruments and maintains and services them.

laTenT FingerprinT UniT The latent fingerprint unit processes and exam- ines evidence for latent fingerprints when they are submitted in conjunction with other laboratory examinations.

polygraph UniT The polygraph, or lie detector, has become an essential tool of the criminal investigator rather than the forensic scientist. However, during the formative years of polygraph technology, many police agencies incorpo- rated this unit into the laboratory’s administrative structure, where it some- times remains today. In any case, its functions are handled by people trained in the techniques of criminal investigation and interrogation (see Figure 10).

VoiceprinT analysis UniT In cases involving telephoned threats or tape- recorded messages, investigators may require the skills of the voiceprint anal- ysis unit to tie the voice to a particular suspect. To this end, a good deal of casework has been performed with the sound spectrograph, an instrument that transforms speech into a visual graphic display called a voiceprint. The validity of this technique as a means of personal identification rests on the premise that the sound patterns produced in speech are unique to the indi- vidual and that the voiceprint displays this uniqueness.

FigUre 10 An individual undergoing a polygraph test. Courtesy ZUMA Press, Inc./Alamy

16

INTRODUCTION

CRIME-SCENE INVESTIGATION UNIT The concept of incorporating crime- scene evidence collection into the services forensic laboratories offer is slowly gaining ground in the United States. This unit dispatches specially trained personnel (civilian and/or police) to the crime scene to collect and preserve physical evidence that will be processed at the crime laboratory.

Whatever the organizational structure of a forensic science laboratory may be, specialization must not impede the overall coordination of services demanded by today’s criminal investigator. Laboratory administrators need to keep open the lines of communication between analysts (civilian and uniformed), crime-scene investigators, and police personnel. Inevitably, forensic investigations require the skills of many individuals. One notoriously high-profi le investigation illustrates this process: the search for the source of the anthrax letters mailed shortly after September 11, 2001. Figure 11 shows one of the letters and illustrates the multi- tude of skills required in the investigation—skills possessed by forensic chemists and biologists, fi ngerprint examiners, and forensic document examiners.

OTHER FORENSIC SCIENCE SERVICES

Even though this text is devoted to describing the services normally provided by a crime laboratory, the fi eld of forensic science is by no means limited to the areas covered in this article. A number of specialized forensic science ser- vices outside the crime laboratory are routinely available to law enforcement personnel. These services are important aids to a criminal investigation and require the involvement of individuals who have highly specialized skills.

Three specialized forensic services—forensic pathology, forensic anthro- pology, and forensic entomology—are frequently employed at a murder scene. Other services, such as those discussed next, are used in a wide variety of criminal investigations.

FORENSIC PSYCHIATRY Forensic psychiatry is a specialized area that exam- ines the relationship between human behavior and legal proceedings. Foren- sic psychiatrists are retained for both civil and criminal litigations. In civil cases, they typically perform tasks such as determining whether an individual is competent to make decisions about preparing a will, settling property, or refusing medical treatment. In criminal cases, forensic psychologists evalu- ate behavioral disorders and determine whether defendants are competent to stand trial. Forensic psychiatrists also examine behavior patterns of criminals as an aid in developing a suspect’s behavioral profi le.

FORENSIC ODONTOLOGY Practitioners of forensic odontology help identify vic- tims based on dental evidence when the body is in an unrecognizable state. Teeth are composed of enamel, the hardest substance in the body. Because of enamel’s resilience, the teeth outlast tissues and organs during decomposition. The char- acteristics of teeth, their alignment, and the overall structure of the mouth pro- vide individual evidence for identifying a specifi c person. Based on dental records such as X-rays and dental casts, even a photograph of the person’s smile, a set of dental remains can be matched to a suspected victim. Another application of forensic odontology to criminal investigations is bite mark analysis. Bite marks are sometimes left on a victim of assault. A forensic odontologist can compare the marks left on a victim to the tooth structure of the suspect (see Figure 12 ). FORENSIC ENGINEERING Forensic engineers are concerned with failure anal- ysis, accident reconstruction, and causes and origins of fi res and explosions. Forensic engineers answer questions such as these: How did an accident or structural failure occur? Were the parties involved responsible? If so, how were they responsible? Accident scenes are examined, photographs are re- viewed, and any mechanical objects involved are inspected.

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Take a Virtual Tour of a Forensic Laboratory www.mycrimekit.com

17

INTRODUCTION

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18

INTRODUCTION

FORENSIC COMPUTER AND DIGITAL ANALYSIS Forensic computer science is a new and fast-growing fi eld that involves identifying, collecting, preserving, and examining information derived from computers and other digital devices, such as cell phones. Law enforcement aspects of this work normally involve recovering deleted or overwritten data from a computer’s hard drive and tracking hacking activities within a compromised system.

Quick Review • The development of crime laboratories in the United States has been char-

acterized by rapid growth accompanied by a lack of national and regional planning and coordination.

• Four major reasons for the increase in the number of crime laboratories in the United States since the 1960s are as follows: (1) The requirement to advise criminal suspects of their constitutional rights and their right of im- mediate access to counsel has all but eliminated confessions as a routine investigative tool. (2) There has been a staggering increase in crime rates in the United States. (3) All illicit-drug seizures must be sent to a forensic laboratory for confi rmatory chemical analysis before the case can be adjudi- cated in court. (4) DNA profi ling was developed and is now often required.

• The technical support provided by crime laboratories can be assigned to fi ve basic services: the physical science unit, the biology unit, the fi rearms unit, the document examination unit, and the photography unit.

• Some crime laboratories offer optional services such as toxicology, fi nger- print analysis, polygraph administration, voiceprint analysis, and crime- scene investigation.

• Special forensic science services available to the law enforcement commu- nity include forensic pathology, forensic anthropology, forensic entomol- ogy, forensic psychiatry, forensic odontology, forensic engineering, and forensic computer and digital analysis.

FIGURE 12 (a) A bite mark on a victim’s body. (b) Comparison to a suspect’s teeth. David Sweet, DMD, PhD, DABFP, Director BOLD Forensic Laboratory, Vancouver, BC, Canada

(a) (b)

19

INTRODUCTION

Functions of the Forensic Scientist Although a forensic scientist relies primarily on scientifi c knowledge and skill, only half of the job is performed in the laboratory. The other half takes place in the courtroom, where the ultimate signifi cance of the evidence is determined. The forensic scientist must not only analyze physical evidence but also per- suade a jury to accept the conclusions derived from that analysis.

ANALYZING PHYSICAL EVIDENCE

First and foremost, the forensic scientist must be skilled in applying the prin- ciples and techniques of the physical and natural sciences to analyze the many types of physical evidence that may be recovered during a criminal investiga- tion. Of the three major avenues available to police investigators for assistance in solving a crime—confessions, eyewitness accounts by victims or witnesses, and the evaluation of physical evidence retrieved from the crime scene—only physical evidence is free of inherent error or bias.

Criminal cases are replete with examples of individuals who were incor- rectly charged with and convicted of committing a crime because of faulty memories or lapses in judgment. For example, investigators may be led astray during their preliminary evaluation of the events and circumstances sur- rounding the commission of a crime. These errors might be compounded by misleading eyewitness statements and inappropriate confessions. These same concerns don’t apply to physical evidence.

What about physical evidence allows investigators to sort out facts as they are and not as they want them to be? The hallmark of physical evidence is that it must undergo scientifi c inquiry. Science derives its integrity from adherence to strict guidelines that ensure the careful and systematic collection, organiza- tion, and analysis of information—a process known as the scientifi c method . The underlying principles of the scientifi c method provide a safety net to en- sure that the outcome of an investigation is not tainted by human emotion or compromised by distorting, belittling, or ignoring contrary evidence.

The scientifi c method begins by formulating a question worthy of inves- tigation, such as who committed a particular crime. The investigator next formulates a hypothesis, a reasonable explanation proposed to answer the question. What follows is the basic foundation of scientifi c inquiry: the testing of the hypothesis through experimentation. The testing process must be thor- ough and recognized by other scientists as valid. Scientists and investigators must accept the experimental fi ndings even when they wish they were differ- ent. Finally, when the hypothesis is validated by experimentation, it becomes suitable as scientifi c evidence, appropriate for use in a criminal investigation and, ultimately, available for admission in a court of law.

DETERMINING ADMISSIBILITY OF EVIDENCE In rejecting the scientifi c validity of the lie detector (polygraph), the District of Columbia Circuit Court in 1923 set forth what has since become a standard guideline for determining the judicial admissibility of scientifi c examinations. In Frye v. United States, 2 the court ruled that, in order to be admitted as evidence at trial, the questioned procedure, tech- nique, or principles must be “generally accepted” by a meaningful segment of the relevant scientifi c community. In practice, this approach requires the pro- ponent of a scientifi c test to present to the court a collection of experts who can testify that the scientifi c issue before the court is generally accepted by the relevant members of the scientifi c community. Furthermore, in determining whether a novel technique meets criteria associated with “general acceptance,” courts have frequently taken note of books and papers written on the subject, as well as prior judicial decisions relating to the reliability and general acceptance of the technique. In recent years many observers have questioned whether this

scientifi c method A process that uses strict guidelines to ensure careful and systematic collection, organization, and analysis of information.

20

INTRODUCTION

approach is fl exible enough to deal with new scientifi c issues that may not have gained widespread support within the scientifi c community.

The Federal Rules of Evidence offer an alternative to the Frye standard, one that some courts believe espouses a more fl exible guideline for admitting scientifi c evidence. Part of the Federal Rules of Evidence governs the admis- sibility of all evidence, including expert testimony, in federal courts, and many states have adopted codes similar to those of the Federal Rules. Specifi cally, Rule 702 of the Federal Rules of Evidence sets a different standard from “gen- eral acceptance” for admissibility of expert testimony. Under this standard, a witness “qualifi ed as an expert by knowledge, skill, experience, training, or education” may offer expert testimony on a scientifi c or technical matter if “(1) the testimony is based on suffi cient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.”

In a landmark ruling in the 1993 case of Daubert v. Merrell Dow Pharma- ceuticals, Inc., 3 the U.S. Supreme Court (see Figure 13 ) asserted that “general acceptance,” or the Frye standard, is not an absolute prerequisite to the admis- sibility of scientifi c evidence under the Federal Rules of Evidence. According to the Court, the Rules of Evidence—especially Rule 702—assign to the trial judge the task of ensuring that an expert’s testimony rests on a reliable foun- dation and is relevant to the case. Although this ruling applies only to federal courts, many state courts are expected to use this decision as a guideline in setting standards for the admissibility of scientifi c evidence.

JUDGING SCIENTIFIC EVIDENCE In Daubert, the Court advocates that trial judges assume the ultimate responsibility for acting as a “gatekeeper” who determines the admissibility and reliability of scientifi c evidence presented in their courts. The Court offered some guidelines as to how a judge can gauge the veracity of scientifi c evidence, emphasizing that the inquiry should be fl ex- ible. Suggested areas of inquiry include the following:

1. Whether the scientifi c technique or theory can be (and has been) tested 2. Whether the technique or theory has been subject to peer review and

publication

FIGURE 13 A sketch of a U.S. Supreme Court hearing. © Art Lien, Court Artist

21

INTRODUCTION

3. The technique’s potential rate of error 4. The existence and maintenance of standards controlling the technique’s

operation 5. Whether the scientifi c theory or method has attracted widespread accep-

tance within a relevant scientifi c community

Some legal experts have expressed concern that abandoning Frye ’s general-acceptance test will result in the introduction of absurd and irrational pseudoscientifi c claims in the courtroom. The Supreme Court rejected these concerns, pointing out the inherent strengths of the US judicial process in identifying unreliable evidence:

In this regard the respondent seems to us to be overly pessimistic about the capa- bilities of the jury and of the adversary system generally. Vigorous cross-examina- tion, presentation of contrary evidence, and careful instruction on the burden of proof are the traditional and appropriate means of attacking shaky but admissible evidence.

In a 1999 decision, Kumho Tire Co., Ltd. v. Carmichael, 4 the Court unani- mously ruled that the “gatekeeping” role of the trial judge applied not only to scientifi c testimony but to all expert testimony:

We conclude that Daubert ’s general holding—setting forth the trial judge’s gen- eral “gatekeeping” obligation—applies not only to testimony based on “scientifi c” knowledge, but also to testimony based on “technical” and “other specialized” knowledge . . . . We also conclude that a trial court may consider one or more of the more specifi c factors that Daubert mentioned when doing so will help determine that testimony’s reliability. But, as the Court stated in Daubert, the test of reliability is “fl exible,” and Daubert ’s list of specifi c factors neither necessarily nor exclusively applies to all experts in every case.

The case of Coppolino v. State 5 (examined more closely in the Case Files feature) exemplifi es the fl exibility and wide discretion that the Daubert ruling, twenty-fi ve years later, apparently gave to trial judges in matters of scientifi c inquiry. The issue in question was whether the results of a new procedure that has not been widely accepted in the scientifi c community are necessarily inadmissible as evidence. The court rejected this argument, recognizing that researchers must devise new scientifi c tests to solve the special problems that continually arise in the forensic laboratory.

The Coppolino ruling acknowledged that even well-established scientifi c procedures were once new and unproved and noted the court’s duty to protect the public when weighing the admissibility of a new test. In the words of the con- curring opinion, “Society need not tolerate homicide until there develops a body of medical literature about some particular lethal agent.” The court emphasized, however, that although these tests may be new and unique, they are admissible only if they are based on scientifi cally valid principles and techniques.

PROVIDING EXPERT TESTIMONY

Because the results of their work may be a factor in determining a person’s ultimate guilt or innocence, forensic scientists may be required to testify about their methods and conclusions at a trial or hearing.

Trial courts have broad discretion in accepting an individual as an expert witness on any particular subject. Generally, if a witness can establish to the sat- isfaction of a trial judge that he or she possesses a particular skill or has knowledge in a trade or profession that will aid the court in determining the truth of the mat- ter at issue, that individual will be accepted as an expert witness. Depending on the subject area in question, the court will usually consider knowledge acquired

expert witness An individual whom the court determines to possess knowledge relevant to the trial that is not expected of the average layperson.

22

INTRODUCTION

through experience, training, education, or a combination of these as suffi cient grounds for qualifi cation as an expert witness.

In court, an expert witness may be asked questions intended to demon- strate his or her ability and competence pertaining to the matter at hand. Competency may be established by having the witness cite educational de- grees, participation in special courses, membership in professional societies, and any professional articles or books published. Also important is the num- ber of years of occupational experience the witness has had in areas related to the matter before the court.

Unfortunately, few schools confer degrees in forensic science. Most chemists, biologists, geologists, and physicists prepare themselves for careers in forensic science by combining training under an experienced examiner with independent study. Of course, formal education in the physical sciences provides a fi rm foun- dation for learning and understanding the principles and techniques of forensic science. Nevertheless, for the most part, courts must rely on training and years of experience as a measurement of the knowledge and ability of the expert.

Before the judge rules on the witness’s qualifi cations, the opposing attor- ney may cross-examine the witness and point out weaknesses in training and knowledge. Most courts are reluctant to disqualify an individual as an expert even when presented with someone whose background is only remotely as- sociated with the issue at hand. The question of what credentials are suitable for qualifi cation as an expert is ambiguous and highly subjective and one that the courts wisely try to avoid.

The weight that a judge or jury assigns to “expert” testimony in subsequent deliberations is, however, quite another matter. Undoubtedly, education and

CASEFILES DR. COPPOLINO’S DEADLY HOUSE CALLS

A frantic late-night telephone call brought a local physician to the Florida home of Drs. Carl and Carmela Coppolino. The physician ar- rived to fi nd Carmela beyond help. Carmela Coppolino’s body, unex- amined by anyone, was then buried in her family’s plot in her home state of New Jersey.

A little more than a month later, Carl married a moneyed social- ite, Mary Gibson. News of Carl’s marriage infuriated Marjorie Farber, a former New Jersey neighbor of Dr. Coppolino who had been a hav- ing an affair with the good doctor. Soon Marjorie had an interest- ing story to recount to investigators: Her husband’s death two years before, although ruled to be from natural causes, had actually been murder! Carl, an anesthesiologist, had given Marjorie a syringe con- taining some medication and told her to inject her husband, William, while he was sleeping. Ultimately, Marjorie claimed, she was unable to inject the full dose and called Carl, who fi nished the job by suf- focating William with a pillow.

Marjorie Farber’s astonishing story was supported in part by Carl’s having recently increased his wife’s life insurance. Carme- la’s $65,000 policy, along with his new wife’s fortune, would keep Dr. Coppolino in high society for the rest of his life. Based on this infor- mation, authorities in New Jersey and Florida obtained exhumation orders for both William Farber and Carmela Coppolino. After both

bodies were examined, Dr. Coppolino was charged with the murders of William and Carmela.

Offi cials decided to try Dr. Coppolino fi rst in New Jersey for the mur- der of William Farber. The Farber autopsy did not reveal any evidence of poisoning but seemed to show strong evidence of strangulation. The absence of toxicological fi ndings left the jury to deliberate the confl icting medical expert testimony versus the sensational story told by a scorned and embittered woman. In the end, Dr. Coppolino was acquitted.

The Florida trial presented another chance to bring Carl Coppolino to justice. Recalling Dr. Coppolino’s career as an anesthesiologist, the prosecution theorized that to commit these murders Coppolino had exploited his access to the many potent drugs used during surgery, specifi cally an injectable paralytic agent called succinylcholine chloride.

Carmela’s body was exhumed, and it was found that Carmela had been injected in her left buttock shortly before her death. Ulti- mately, a completely novel procedure for detecting succinylcholine chloride was devised. With this procedure elevated levels of succinic acid were found in Carmela’s brain, which proved that she had re- ceived a large dose of the paralytic drug shortly before her death. This evidence, along with evidence of the same drug residues in the injection site on her buttock, was presented in the Florida murder trial of Carl Coppolino, who was convicted of second-degree murder.

23

INTRODUCTION

experience have considerable bearing on what value should be assigned to the expert’s opinions. Just as important may be his or her demeanor and ability to explain scientifi c data and conclusions clearly, concisely, and logically to a judge and jury composed of nonscientists. The problem of sorting out the strengths and weaknesses of expert testimony falls to prosecution and defense counsel.

The ordinary or lay witness must testify on events or observations that arise from personal knowledge. This testimony must be factual and, with few excep- tions, cannot contain the personal opinions of the witness. On the other hand, the expert witness is called on to evaluate evidence when the court lacks the expertise to do so. This expert then expresses an opinion as to the signifi cance of the fi nd- ings. The views expressed are accepted only as representing the expert’s opinion and may later be accepted or ignored in jury deliberations (see Figure 14 ).

The expert cannot render any view with absolute certainty. At best, he or she may only be able to offer an opinion based on a reasonable scientifi c cer- tainty derived from training and experience. Obviously, the expert is expected to defend vigorously the techniques and conclusions of the analysis, but at the same time he or she must not be reluctant to discuss impartially any fi nd- ings that could minimize the signifi cance of the analysis. The forensic scientist should not be an advocate of one party’s cause but an advocate of truth only. An adversary system of justice must give the prosecutor and defense ample opportunity to offer expert opinions and to argue the merits of such testi- mony. Ultimately, the duty of the judge or jury is to weigh the pros and cons of all the information presented when deciding guilt or innocence.

The necessity for the forensic scientist to appear in court has been im- posed on the criminal justice system by a 2009 U.S. Supreme Court case, Melendez-Diaz v . Massachusetts. 6 The Melendez-Diaz decision addressed the practice of using evidence affi davits or laboratory certifi cates in lieu of in- person testimony by forensic analysts. In its reasoning, the Court relied on a previous ruling, Crawford v. Washington 7 where it explored the meaning of the Confrontation Clause of the Sixth Amendment. In the Crawford case, a recorded statement by a spouse was used against her husband in his prosecu- tion. Crawford argued that this was a violation of his right to confront wit- nesses against him under the Sixth Amendment, and the Court agreed. Using

FIGURE 14 An expert witness testifying in court. Taylor Jones/ZUMA Press/Newscom

24

INTRODUCTION

the same logic in Melendez-Diaz, the Court reasoned that introducing forensic science evidence via an affi davit or a certifi cate denied a defendant the oppor- tunity to cross-examine the analyst. In 2011, the Supreme Court reaffi rmed the Melendez-Diaz decision in the case of Bullcoming v. New Mexico8 by rejecting a substitute expert witness in lieu of the original analyst:

The question presented is whether the Confrontation Clause permits the prosecu- tion to introduce a forensic laboratory report containing a testimonial certifi cation— made for the purpose of proving a particular fact—through the in-court testimony of a scientist who did not sign the certifi cation or perform or observe the test re- ported in the certifi cation. We hold that surrogate testimony of that order does not meet the constitutional requirement. The accused’s right is to be confronted with the analyst who made the certifi cation, unless that analyst is unavailable at trial, and the accused had an opportunity, pretrial, to cross-examine that particular scientist.

FURNISHING TRAINING IN

THE PROPER RECOGNITION,

COLLECTION, AND PRESERVATION

OF PHYSICAL EVIDENCE

The competence of a laboratory staff and the sophistication of its analytical equipment have little or no value if relevant evidence cannot be properly rec- ognized, collected, and preserved at the site of a crime. For this reason, the forensic staff must have responsibilities that will infl uence the conduct of the crime-scene investigation.

The most direct and effective response to this problem has been to dispatch specially trained evidence-collection technicians to the crime scene. A growing number of crime laboratories and the police agencies they service keep trained “evidence technicians” on 24-hour call to help criminal investigators retrieve evidence. These technicians are trained by the laboratory staff to recognize and gather pertinent physical evidence at the crime scene. They are assigned to the laboratory full-time for continued exposure to forensic techniques and procedures. They have at their disposal all the proper tools and supplies for proper collection and packaging of evidence for future scientifi c examination.

Unfortunately, many police forces still have not adopted this approach. Often a patrol offi cer or detective collects the evidence. The individual’s effectiveness in this role depends on the extent of his or her training and working relation- ship with the laboratory. For maximum use of the skills of the crime laboratory, training of the crime-scene investigator must go beyond superfi cial classroom lectures to involve extensive personal contact with the forensic scientist. Each must become aware of the other’s problems, techniques, and limitations.

The training of police offi cers in evidence collection and their familiariza- tion with the capabilities of a crime laboratory should not be restricted to a select group of personnel on the force. Every offi cer engaged in fi eldwork, whether it be traffi c, patrol, investigation, or juvenile control, often must pro- cess evidence for laboratory examination. Obviously, it would be diffi cult and time consuming to give everyone the in-depth training and attention that a qualifi ed criminal investigator requires. However, familiarity with crime labo- ratory services and capabilities can be gained through periodic lectures, labo- ratory tours, and dissemination of manuals prepared by the laboratory staff that outline the proper methods for collecting and submitting physical evi- dence to the laboratory (see Figure 15 ).

MyCrimeKit WebExtra 2

Watch a Forensic Expert Witness Testify—I www.mycrimekit.com

MyCrimeKit WebExtra 3

Watch a Forensic Expert Witness Testify—II www.mycrimekit.com

25

INTRODUCTION

Quick Review • A forensic scientist must be skilled in applying the principles and tech-

niques of the physical and natural sciences to analyzing evidence that may be recovered during a criminal investigation.

• The cases Frye v. United States and Daubert v. Merrell Dow Pharmaceuti- cals, Inc. set guidelines for determining the admissibility of scientifi c evi- dence into the courtroom.

• An expert witness evaluates evidence based on specialized training and experience.

• Forensic scientists participate in training law enforcement personnel in the proper recognition, collection, and preservation of physical evidence.

EXPLORING FORENSIC SCIENCE

ON THE INTERNET

There are no limits to the amount or type of information that can be found on the Internet. The fi elds of law enforcement and forensic science have not been left behind by advancing computer technology. Extensive information about forensic science is available on the Internet. The types of information available on websites range from simple explanations of the various fi elds of forensics to intricate details of crime-scene reconstruction. People can also fi nd infor- mation on which colleges offer degree programs in forensics and webpages posted by law enforcement agencies that detail their activities as well as em- ployment opportunities.

GENERAL FORENSICS SITES

Reddy’s Forensic Home Page ( www.forensicpage.com ) is a valuable starting point. This site is a collection of forensic webpages in categories such as new links in forensics; general forensic information sources; associations, colleges,

FIGURE 15 Representative evidence-collection guides prepared by various governmental agencies.

26

INTRODUCTION

and societies; literature and journals; forensic laboratories; general webpages; forensic-related mailing lists and newsgroups; universities; conferences; and various forensic fi elds of expertise.

Another website offering a multitude of information related to forensic science is Zeno’s Forensic Site ( www.forensic.to/forensic.html ). Here users can fi nd links related to forensic education and expert consultation, as well as a wealth of information concerning specifi c fi elds of forensic science.

A comprehensive and useful website for those interested in law enforce- ment is Offi cer.com ( www.offi cer.com ). This comprehensive collection of criminal justice resources is organized into easy-to-read subdirectories that relate to topics such as law enforcement agencies, police association and or- ganization sites, criminal justice organizations, law research pages, and police mailing-list directories.

WEBSITES ON SPECIFIC TOPICS

AN INTRODUCTION TO FORENSIC FIREARM IDENTIFICATION This website contains an extensive collection of information relating to the identifi cation of fi rearms. An individual can explore in detail how to examine bullets, car- tridge cases, and clothing for gunshot residues and suspect shooters’ hands for primer residues. Information on the latest technology involving the auto- mated fi rearms search system IBIS can also be found on this site.

CARPENTER’S FORENSIC SCIENCE RESOURCES This site provides a bibliog- raphy involving forensic evidence. For example, the user can fi nd references about DNA, fi ngerprints, hairs, fi bers, and questioned documents as they re- late to crime scenes and assist investigations. This website is an excellent place to start a research project in forensic science.

CRIME SCENE INVESTIGATOR NETWORK For those who are interested in learning the process of crime-scene investigation, this site provides detailed guidelines and information regarding crime-scene response and the collection and preservation of evidence. For example, information concerning the pack- aging and analysis of bloodstains, seminal fl uids, hairs, fi bers, paint, glass, fi rearms, documents, and fi ngerprints can be found through this website. It explains the importance of inspecting the crime scene and the impact forensic evidence has on the investigation.

CRIMES AND CLUES Users interested in learning about the forensic aspects of fi ngerprinting will fi nd this to be a useful and informative website. The site covers the history of fi ngerprints, as well as subjects pertaining to the devel- opment of latent fi ngerprints. The user will also fi nd links to other websites covering a variety of subjects pertaining to crime-scene investigation, docu- mentation of the crime scene, and expert testimony.

INTERACTIVE INVESTIGATOR—DÉTECTIVE INTERACTIF At this outstanding site, visitors can obtain general information and an introduction to the main aspects of forensic science from a database on the subject. They can also ex- plore actual evidence gathered from notorious crime scenes. Users will be able to employ deductive skills and forensic knowledge while playing an inter- active game in which they must help Detective Wilson and Detective Marlow solve a gruesome murder.

THE CHEMICAL DETECTIVE This site offers descriptions of relevant forensic science disciplines. Topics such as fi ngerprints, fi re and arson, and DNA analy- sis are described in informative layperson’s terms. Case histories describe the application of forensic evidence to criminal investigations. Emphasis is placed

MyCrimeKit WebExtra 4

An Introduction to Forensic Firearm Identifi cation www.mycrimekit.com

MyCrimeKit WebExtra 5

Carpenter’s Forensic Science Resources www.mycrimekit.com

MyCrimeKit WebExtra 6

Crime Scene Investigator Network www.mycrimekit.com

MyCrimeKit WebExtra 7

Crimes and Clues www.mycrimekit.com

MyCrimeKit WebExtra 8

Interactive Investigator www.mycrimekit.com

MyCrimeKit WebExtra 9

The Chemical Detective www.mycrimekit.com

27

INTRODUCTION

on securing and documenting the crime scene. The site directs the reader to other important forensic links.

QUESTIONED-DOCUMENT EXAMINATION This basic, informative webpage answers frequently asked questions concerning document examination, ex- plains the application of typical document examinations, and details the basic facts and theory of handwriting and signatures. There are also links to noted document examination cases that present the user with real-life applications of forensic document examination.

MyCrimeKit WebExtra 10

Questioned-Document Examination www.mycrimekit.com

CHAPTER REVIEW

• Forensic science is the application of science to criminal and civil laws that are enforced by police agencies in a criminal justice system.

• The fi rst system of personal identifi cation was called anthro- pometry. It distinguished one individual from another based on a series of bodily measurements.

• Forensic science owes its origins to individuals such as Bertil- lon, Galton, Lattes, Goddard, Osborn, and Locard, who devel- oped the principles and techniques needed to identify and compare physical evidence.

• Locard’s exchange principle states that, when two objects come into contact with each other, a cross-transfer of materi- als occurs that can connect a criminal suspect to his or her victim.

• The development of crime laboratories in the United States has been characterized by rapid growth accompanied by a lack of national and regional planning and coordination.

• Four major reasons for the increase in the number of crime laboratories in the United States since the 1960s are as fol- lows: (1) The requirement to advise criminal suspects of their constitutional rights and their right of immediate access to counsel has all but eliminated confessions as a routine in- vestigative tool. (2) There has been a staggering increase in crime rates in the United States. (3) All illicit-drug sei- zures must be sent to a forensic laboratory for confi rmatory

chemical analysis before the case can be adjudicated in court. (4) DNA profi ling was developed and is now often required.

• The technical support provided by crime laboratories can be assigned to fi ve basic services: the physical science unit, the biology unit, the fi rearms unit, the document examination unit, and the photography unit.

• Some crime laboratories offer optional services such as toxi- cology, fi ngerprint analysis, polygraph administration, voice- print analysis, and crime-scene investigation.

• Special forensic science services available to the law enforce- ment community include forensic pathology, forensic anthro- pology, forensic entomology, forensic psychiatry, forensic odontology, forensic engineering, and forensic computer and digital analysis.

• A forensic scientist must be skilled in applying the principles and techniques of the physical and natural sciences to analyzing evi- dence that may be recovered during a criminal investigation.

• The cases Frye v. United States and Daubert v. Merrell Dow Pharmaceuticals, Inc. set guidelines for determining the admissibility of scientifi c evidence into the courtroom.

• An expert witness evaluates evidence based on specialized training and experience.

• Forensic scientists participate in training law enforcement personnel in the proper recognition, collection, and preserva- tion of physical evidence.

KEY TERMS

expert witness Locard’s exchange principle scientifi c method

REVIEW QUESTIONS

1. The application of science to law describes ______________ .

2. The Spaniard ______________ published the fi rst writings about the detection of poisons and the effects of poisons on animals, and he is considered the father of forensic toxicology.

3. A system of personal identifi cation using a series of bodily measurements was fi rst devised by ______________ , and he called it ______________ .

28

INTRODUCTION

4. The fi ctional exploits of ______________ excited the imagi- nation of an emerging generation of forensic scientists and criminal investigators.

5. One of the fi rst functional crime laboratories was formed in Lyons, France, in 1910 under the direction of ____________ , who developed ____________ , a theory stating that there is mutual transfer of material when two objects make con- tact with each other.

6. The application of science to criminal investigation was advocated by the Austrian magistrate ______________ .

7. True or False: The important advancement in the fi elds of blood typing and document examination were made in the early part of the twentieth century. ______________

8. The Italian scientist ______________ devised the fi rst workable procedure for typing dried bloodstains.

9. Early efforts at applying scientifi c principles to document examination are associated with ______________.

10. The fi rst DNA profi ling test was developed by ______________ in 1984, and it was fi rst used in 1986 to identify the murderer of two young English girls.

11. True or False: Computerized databases exist for fi ngerprints, bullets, cartridge cases, and DNA. ______________

12. The fi rst forensic laboratory in the United States was created in 1923 by the ______________ Police Department.

13. Although no national system of forensic laboratories exists in the United States, the state of ______________ is an ex- cellent example of a geographical area in the United States that has created a system of integrated regional and satellite laboratories.

14. A decentralized system of crime laboratories currently exists in the United States under the auspices of various governmen- tal agencies at the ______________ , ______________ , ______________ , and ______________ levels of government.

15. In contrast to the United States, Britain has a crime labo- ratory system characterized by a national system of ______________ laboratories.

16. Four important federal agencies offering forensic services are ______________ , ______________ , ______________ , and ______________ .

17. The application of chemistry, physics, and geology to the identifi cation and comparison of crime-scene evidence is the function of the ______________ unit of a crime laboratory.

18. The examination of blood, hairs, fi bers, and botanical mate- rials is conducted in the ______________ unit of a crime laboratory.

19. The examination of bullets, cartridge cases, shotgun shells, and ammunition of all types is the responsibility of the ______________ unit.

20. The study of handwriting and typewriting on questioned documents is carried out by the ______________ unit to ascertain authenticity and/or source.

21. The examination of body fl uids and organs for drugs and poisons is a function of the ______________ unit.

22. The ______________ unit dispatches trained personnel to the scene of a crime to retrieve evidence for laboratory examination.

23. True or False: Special forensic science services available to the law enforcement community include forensic pa- thology, forensic anthropology, and forensic astronomy. ______________

24. The “general acceptance” principle, which serves as a crite- rion for the judicial admissibility of scientifi c evidence, was set forth in the case of ______________ .

25. In the case of ______________ , the Supreme Court ruled that, in assessing the admissibility of new and unique sci- entifi c tests, the trial judge did not have to rely solely on the concept of “general acceptance.”

26. True or False: The U.S. Supreme Court decision in Kumho Tire Co., Ltd. v. Carmichael restricted the “gatekeeping” role of a trial judge to scientifi c testimony only. ______________

27. A Florida case that exemplifi es the fl exibility and wide discre- tion that the trial judge has in matters of scientifi c inquiry is ______________ .

28. A(n) ______________ is a person who can demonstrate a particular skill or has knowledge in a trade or profession that will help the court determine the truth of the matter at issue.

29. True or False: The expert witness’s courtroom demeanor may play an important role in deciding what weight the court will assign to his or her testimony. ______________

30. True or False: The testimony of an expert witness incorpo- rates his or her personal opinion relating to a matter he or she has either studied or examined. ______________

31. True or False: In 2004, the U.S. Supreme Court addressed issues relating to the Confrontation Clause of the Sixth Amendment in the case of Crawford v. Washington . ______________

32. The 2009 U.S. Supreme Court decision ______________ ad- dressed the practice of using affi davits in lieu of in-person testimony by forensic examiners.

33. The ability of the investigator to recognize and collect crime-scene evidence properly depends on the amount of ______________ received from the crime laboratory.

29

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DESIGN SERVICES OF

S4carliSle Publishing Services

IntroductIon

ApplicAtion And criticAl thinking

1. Most crime labs in the United States are funded and oper- ated by the government and provide services free to police and prosecutors. Great Britain, however, relies on private laboratories that charge fees for their services and keep any profits they make. Suggest potential strengths and weak- nesses of each system.

2. Police investigating an apparent suicide collect the following items at the scene: a note purportedly written by the victim, a revolver bearing very faint fingerprints, and traces of skin and blood under the victim’s fingernails. What units of the crime laboratory will examine each piece of evidence?

3. List at least three advantages of having an evidence-collection unit process a crime scene instead of a patrol officer or detective.

4. What legal issue was raised on appeal by the defense in Carl Coppolino’s Florida murder trial? What court ruling is most rel- evant to the decision to reject the appeal? Explain your answer.

5. A timeline of Forensic Science The following images de- pict different types of evidence or techniques for analyzing evidence. Place the images in order pertaining to the time in history (least recent to most recent) at which each type of evidence or technique was first introduced. Do this using the letters assigned to the images.

(A) (D)(B) (C)

(E) (G)(F)

(A), (B) Dorling Kindersley Media Library; (D) Photolibrary.com; (E) lkordela/Shutterstock; (F) Getty Images, Inc. - Hulton Archive

Photos; (G) Getty Images Inc. - PhotoDisc

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INTRODUCTION

6. Evidence Processing at the Crime Laboratory You are the evidence technician at the front desk of the state crime lab. You receive the following items of evidence to check in on a very busy day. You must indicate which unit each piece of evidence must be sent to for analysis. Your

crime lab has a criminalistics (physical science) unit, a drug unit, a biology unit, a fi rearms unit, a document exami- nation unit, a toxicology unit, a latent fi ngerprinting unit, an anthropology unit, and a forensic computer and digital analysis unit.

A.

B.

C.

D.

E.

F.

G.

H.

I.

J.

K.

L.

M.

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EndnotEs

1. Two excellent references are André A. Moenssens, Carol E. Henderson, and Sharon Gross Portwood, Scientific Evidence in Civil and Criminal Cases, 5th ed. (New York: Foundation Press, 2007); and Werner U. Spitz, ed., Medicolegal Investigation of Death, 4th ed. (Springfield, Ill.: Charles C. Thomas, 2006).

2. 293 Fed. 1013 (D.C. Cir. 1923).

3. 509 U.S. 579 (1993).

4. 526 U.S. 137 (1999).

5. 223 So. 2d 68 (Fla. App. 1968), app. dismissed, 234 So. 2d (Fla. 1969), cert. denied, 399 U.S. 927 (1970).

6. 129 S. Ct. 2527 U.S. Mass., (2009).

7. 541 U.S. 36, 124 S. Ct. 1354, 158 L.Ed. 2d 177 (2004).

8. 564 U.S. 131 S. Ct. 2705, 180 L.Ed. 2d 610 (2011).

(A) (E)(B) (C) (D)

(I)(F) (G) (H)

(J) (M)(K) (L)

IntroductIon

(A) and (E) Getty Images Inc. - Stone Allstock; (B) Michael P. Gadomski/Photo Researchers Inc.; (C) Mikael Karlsson/Arresting Images; (D) German Meneses Photography; (F) Getty Images Inc. - Photodisc/Royalty Free; (G) CORBIS - NY; (H), (J), (M) Dorling Kindersley Media Library; (L) Frank Bean/Getty Images; (I) Alamy Images; (K) Corbis RF

32

JONBENET RAMSEY: WHO DID IT? Patsy and John Ramsey were in the upper crust of Boulder, Colorado, society. In the span of fi ve short years, John had built his computer company into a billion-dollar corporation. In addition to fi nancial success, the Ramseys also had a beautiful 6-year-old daughter, JonBenet.

Just after fi ve a.m. on December 26, 1996, Patsy Ramsey awoke and walked downstairs to her kitchen. At the foot of the staircase, she found a two-and-a-half-

page note saying that JonBenet had been kidnapped. The note contained a ransom demand of $118,000. When the police arrived to investigate, it was quite appar- ent that JonBenet was missing.

In retrospect, some serious mistakes were made in securing the crime scene, the Ramsey household. Initially, the police conducted a cursory search of the house but failed to fi nd JonBenet. They did not seal the house off; in fact, four of the Ramseys’ friends along with their pastor were let into the home and allowed to move about at will. John was permitted to leave the premises unattended for one and a half hours. One hour after his return, John and two of his friends searched the house again. This time John went down into the basement, where he discovered JonBenet’s body. He removed a white

blanket from JonBenet and carried her upstairs, placing the body on the living room fl oor.

The murder of JonBenet Ramsey remains as baf- fl ing a mystery today as it was on the fi rst day of its in- vestigation. Ample physical evidence supports both the theory that the crime was committed by an outsider and the competing theory that JonBenet was murdered by someone who resided in the Ramsey household. Perhaps better care at securing and processing the crime scene would have resolved some of the crime’s outstanding questions.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Discuss the responsibilities of the fi rst police offi cer who

arrives at the crime scene. • Comprehend the role of the lead investigator in coordinating

the crime-scene search. • Describe the conditions at the crime scene that should be

given particular notice. • Understand the various search patterns investigators can use

to systematically search the crime scene for evidence. • Appreciate the necessity of documenting all initial

observations and evidence collected.

Securing and Searching

the Crime Scene

© Douglas Keister/Corbis. All Rights Reserved

From Chapter 2 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

SECURING AND SEARCHING THE CRIME SCENE

F orensic science begins at the crime scene. To be useful to investigators, evidence at a crime scene must be preserved and recorded in its original condition as much as possible. Failure to protect a crime scene properly

may result in the destruction or altering of evidence, which can hinder the search for the perpetrator by misleading investigators about the facts of the incident.

Securing the Crime Scene The fi rst offi cer to arrive at the scene of a crime is responsible for taking steps to preserve and protect the area to the greatest extent possible. The offi cer should not let his or her guard down; the scene should always be treated as though the crime were still occurring until it is proved otherwise. Arriving offi cers should immediately ascertain that the perpetrator is no longer in the immediate area of the crime scene and is not a threat to anyone at or near the crime scene. Special note should be taken of any vehicles or people leaving the scene.

Of course, fi rst priority should be given to obtaining medical assistance for individuals in need of it. If medical assistance is needed, the offi cer should direct medical workers to approach the body by an indirect route to minimize the possibility of disturbing evidence. This pathway should later be used by investigative personnel for the same reason. The fi rst responding offi cer must quickly evaluate the victim’s condition before the victim is taken to a medical facility. The offi cer must also record any statements made by the victim and instruct the emergency medical personnel to record any statements the victim makes on the way to the hospital. This information should later be included in notes.

The offi cer should call for any backup or investigative personnel required and, as soon as possible, detain all potential suspects or witnesses still at the scene. The offi cer must identify all individuals at the scene, including bystand- ers and medical personnel. At the same time, he or she should exclude all unauthorized personnel from the scene. This includes family and friends of the victim, who should be shown as much compassion as possible.

The fi rst responder(s) are responsible for establishing the boundaries of the scene to be protected. The boundaries should encompass the center of the scene where the crime occurred, any paths of entry or exit, and any areas where evidence may have been discarded or moved. For indoor scenes this may include anything from a single room to an entire house and yard. The center of the crime scene is usually apparent, and a suffi cient area around this spot should be closed off. The boundaries of an outdoor crime scene are more diffi cult to determine and can span miles, especially if a vehicle is involved. The offi cer should initially denote the boundaries of the scene using crime- scene tape, ropes, or traffi c cones (see Figure 1 ). As additional offi cers arrive, investigators should immediately take measures to isolate the area around the taped-off section. Police barricades, along with the strategic positioning of guards, will prevent unauthorized access to the area. Only investigative per- sonnel assigned to the scene should be admitted. The responding offi cers must keep an accurate log of who enters and exits the scene and the time at which they do so.

Sometimes the exclusion of unauthorized personnel proves to be more diffi cult than expected. Crimes of violence are especially susceptible to atten- tion by higher-level police offi cials and members of the media, as well as by emotionally charged neighbors and curiosity seekers. Every individual who enters the scene has the potential to destroy physical evidence, even if by

34

SECURING AND SEARCHING THE CRIME SCENE

unintentional carelessness. To exercise proper control over the crime scene, the offi cer charged with the responsibility for protecting it must have the author- ity to exclude everyone, including fellow police offi cers not directly involved in processing the site or in conducting the investigation. Seasoned criminal investigators are always prepared to relate horror stories about crime scenes where physical evidence was rendered totally valueless by hordes of people who, for one reason or another, tramped through the site. Securing and isolat- ing the crime scene are critical steps in an investigation, the accomplishment of which is the mark of a trained and professional crime-scene investigative team. It is also important to park the crime-scene vehicle where it will not de- stroy evidence but also be secure and easily accessible.

It is worth noting that personnel should never do anything while at the crime scene—including smoking, eating, drinking, or littering—that might alter the scene. No aspects of the scene, including a body at a death scene, should be moved or disturbed unless they pose a serious threat to investi- gating offi cers or bystanders. This means that no one should open or close faucets or fl ush toilets at the scene. Also, offi cers should avoid altering tem- perature conditions at the scene by adjusting windows, doors, or the heat or air-conditioning.

Quick Review • The fi rst offi cer arriving on the scene of a crime has the responsibility to

preserve and protect the area to the greatest extent possible. • First priority should be given to obtaining medical assistance for individu-

als in need of it. • Steps must be taken by the fi rst responder to exclude all unauthorized per-

sonnel from the scene and keep an accurate log of who enters and exits the scene and the time at which they do so.

FIGURE 1 The fi rst investigators to arrive must secure the crime scene and establish a perimeter. This perimeter may be delineated by crime-scene tape, ropes, or barricades. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

35

SECURING AND SEARCHING THE CRIME SCENE

Surveying the Crime Scene Once the scene has been secured, with the help of others, a lead investigator will start the process of evaluating the area. The lead investigator will immedi- ately gain an overview of the situation and develop a strategy for the system- atic examination and documentation of the entire crime scene.

THE WALK-THROUGH

The initial survey of the scene is typically called the walk-through . First, the perpetrator’s path of entry and exit should be established. The investigators should then follow an indirect path to the center of the scene, possibly one already established by the fi rst responding offi cer to allow for medical atten- tion. Some investigators attempt to follow the path of the suspect, but this may destroy possible evidence.

Logic dictates that obvious items of crime-scene evidence will fi rst come to the attention of the crime-scene investigator. The investigator must docu- ment and photograph these items. Any fragile evidence, such as shoe and tire impressions, may be secured by the investigator or tagged for the search team. Investigators conducting the fi rst walk-through should carry refl ec- tive numbered markers and place a marker near each item of evidence they locate. These markers will alert other crime-scene personnel to the location of diffi cult-to-observe evidence. The investigators should remember that the crime scene is three-dimensional; evidence may be found on the walls or ceil- ings as well as on the fl oor and other surfaces. It may also be practical to have one or two individuals canvas the area outside the barricaded scene.

The investigator should ask the following questions:

• Is the scene indoors or outdoors? • What is the location of the scene (street address if applicable)? • What are the weather or temperature conditions? • In what type of building and neighborhood is the scene located? • Was there any odor detected by the fi rst responder upon arrival? • Are doors and windows open or closed, locked or unlocked? • Given the states of windows and doors, what are possible points of entry

and exit? • Is anything damaged, out of place, or missing? Are there objects that do

not appear to belong there? • Does an object’s condition suggest that a struggle took place? • Are lights and electrical appliances on or off? • Is food present? Is it in the middle of being prepared, partially eaten, etc.? • Does this scene appear to involve violence? • What are the contents of any ashtrays and trash cans at the crime site? Are

there tooth marks or lipstick on cigarette butts? • What is the state of the bathroom? Are towels wet or dry? Is the toilet seat

up or down? • Are there any places where the suspect could have easily and quickly hid-

den a weapon? • Is there a vehicle nearby? If so, is the engine hot or cold?

Investigators should take particular note of aspects of the scene that suggest the timing of the incident. For example, if today’s newspaper is on the table, it suggests that the incident occurred after the paper was delivered. The investigator’s notes should include answers to basic questions and descriptions of everything observed at the scene. These simple observations may prove signifi cant in the later investigation.

walk-through The initial survey of the crime scene carried out by the lead investigator to gain an overview of the scene in order to formulate a plan for processing the scene.

36

SECURING AND SEARCHING THE CRIME SCENE

The presence or absence of certain evidence can offer key clues to the in- vestigator. For example, objects that appear out of place, such as a child’s toy in the house of a couple without children or relatives without children, may be very important. It is also important to observe whether objects that should be at the scene, such as a television or computer, are missing or displaced.

The presence or absence of evidence may also suggest whether the scene is a primary or secondary scene. A primary scene is one at which the original incident occurred. The secondary scene is a location that became part of the crime by activities after the initial incident, such as using a car to transport a body. If a victim suffered severe injury involving heavy loss of blood but little or no blood is present where the body is found, it is likely to be a secondary scene.

ASSIGNING TASKS

Investigators must establish a center of operations or command center at the scene. Here, members of the investigative team receive their assignments, store their equipment, and meet to discuss aspects of the case. The command center must be located outside the taped-off boundary of the scene and con- tain the basic equipment needed to photograph, sketch, process, and collect evidence. An equipped crime-scene vehicle usually serves the purpose well. If multiple scenes are involved, the command center should also be a center for communicating with investigators at the other scenes.

At the command center, the lead investigator assigns tasks after the initial walk-through. Basic tasks include locating possible evidence, assessing the evidence, processing evidence (e.g., dusting for fi ngerprints and casting foot- prints or tire impressions), and photographing and sketching the scene. The tasks should be carried out in this exact order to properly process the scene. The number of personnel assigned to each task depends on the scene and the discretion of the lead investigator. In some cases, a single crime-scene investi- gator might be required to handle all these tasks.

Quick Review • The lead investigator is responsible for developing a strategy for the sys-

tematic examination and documentation of the entire crime scene. • The lead investigator must gain an overview of the general setting of the

scene. Of particular importance are objects that do not appear to belong or aspects of the scene that may suggest the timing of the incident.

• The presence or absence of evidence may also suggest whether the scene is a primary or secondary scene.

• At the command center, members of the investigative team receive their assignments, store their equipment, congregate to talk about aspects of the case, and communicate with personnel at other crime scenes.

Searching the Crime Scene There are many methods for searching the scene in a logical and systematic fashion to locate evidence. How one carries out a crime-scene search depends on the locale and size of the area, as well as on the actions of the suspect(s) and victim(s) at the scene. When possible, it is advisable to have one person super- vising and coordinating the collection of evidence. Without proper control, the search may be conducted in an atmosphere of confusion with needless duplication of effort. The areas searched must include all probable points of entry and exit used by the criminals. The search team may want to use a simple

primary scene A crime scene at which the original criminal act was perpetrated.

secondary scene A crime scene separate from the primary scene that became part of the crime by its involvement in activities after the initial criminal act was perpetrated.

command center A secure site outside the boundaries of a crime scene where equipment is stored, tasks are assigned, and communication occurs.

37

SECURING AND SEARCHING THE CRIME SCENE

fl ashlight to illuminate surfaces at an oblique angle to reveal latent (hidden) fi ngerprints, handprints, footwear imprints, and other residues.

TYPES OF SEARCH PATTERNS

LINE/STRIP SEARCH PATTERN In the line/strip search pattern , one or two investigators start at the boundary at one end of the scene and walk straight across to the other side. They then move a little farther along the border and walk straight back to the other side (see Figure 2[a] ). This method is best used in scenes where the boundaries are well established because the boundar- ies dictate the beginning and end of the search lines. If the boundary is in- correctly chosen, important evidence may remain undiscovered outside the search area.

GRID SEARCH PATTERN The grid search pattern employs two people per- forming line searches that originate from adjacent corners and form per- pendicular lines (see Figure 2[b] ). One searcher will move in a north-south direction while a simultaneous search is conducted in an east-west direction. Both move back and forth as in the line/strip search pattern. This method is very thorough, but the boundaries must be well established.

SPIRAL SEARCH PATTERN The spiral search pattern usually employs one person. The investigator moves in an inward spiral from the boundary to the center of the scene or in an outward spiral from the center to the boundary (see Figure 2[c] ). The inward spiral method is helpful because the searcher is moving from an area light with evidence to an area where more evidence will most likely be found. Either spiral approach facilitates the location of foot- prints leading away from the scene in any direction. However, it is often dif- fi cult for a searcher to complete a perfect spiral, and evidence could be missed.

line/strip search pattern A search method used by one or two investigators who walk in straight lines across the crime scene.

grid search pattern A search method employed by two or more people who perform overlapping line searches forming a grid.

spiral search pattern A search method in which the investigator moves in an inward spiral from the boundary to the center of the scene or in an outward spiral from the center to the boundary of a scene.

FIGURE 2 (a) Line/strip search pattern; (b) grid search pattern; (c) spiral search pattern; (d) wheel/ray search pattern; (e) quadrant/zone search pattern.

Grid search

Quadrant or zone search

end

start

Spiral search method(c)(b)

(e)Wheel/Ray search(d)

Strip or line search(a)

38

SECURING AND SEARCHING THE CRIME SCENE

WHEEL/RAY SEARCH PATTERN The wheel/ray search pattern employs sev- eral people moving from the boundary straight toward the center of the scene (inward) or from the center straight to the boundary (outward). This method is not preferred because the areas between the “rays” are not searched (see Figure 2[d] ).

QUADRANT/ZONE SEARCH PATTERN The quadrant/zone search pattern involves dividing the scene into zones or quadrants, and team members are assigned to search each section. Each of these sections can be subdivided into smaller sections for smaller teams to search thoroughly (see Figure 2[e] ). This method is best suited for scenes that cover a large area.

VEHICLE SEARCHES If the scene includes a vehicle, the vehicle search must be carefully planned and systematically carried out. The nature of the case de- termines how detailed the search must be. At all times investigators must be careful to avoid contact with surfaces that may contain fi ngerprints such as a steering wheel or door handle. In hit-and-run cases, the outside and undercar- riage of the car must be examined with care. In this case the vehicle itself is the “weapon.” Particular attention is paid to looking for any evidence resulting from a cross-transfer of evidence between the car and the victim; this includes blood, tissue, hair, fi bers, and fabric impressions. Traces of paint or broken glass may be located on the victim or roadway. In a vehicle burglary or theft, the search focuses on the place of entry. Tool marks and fi ngerprints usually are important in these cases. If the car was used for transportation, more at- tention may be given to the interior of the car. However, all areas of the vehicle, inside and outside, should be searched with equal care for physical evidence at the scene, or the vehicle may be towed to a police department garage.

NIGHT SEARCHES Searches during the night are especially diffi cult. Indoors, artifi cial lights frequently can be used. However, it can be very diffi cult out- doors even to determine the boundaries of the scene. When possible, the scene should be taped off, left undisturbed, and guarded until daylight. If impend- ing weather or other circumstances do not allow for waiting until daylight, a perimeter must be estimated and fl oodlights should be set up for the search.

LOCATING EVIDENCE

The purpose of the crime-scene search is to locate physical evidence. What to search for will be determined by the particular circumstances of the crime. This may include footprints, weapons, blood spatter, objects possibly touched by the suspect, trace fi bers, or hairs. For example, in the case of homicide, the search will be centered on the weapon and any type of evidence left as a result of contact between the victim and the assailant. The cross-transfer of evidence, such as hairs, fi bers, and blood, between individuals involved in the crime is particularly useful for linking suspects to the crime site and for corroborating events that transpired during the commission of the crime. Special attention should be paid to the body and the area surrounding it. During the investiga- tion of a burglary, offi cers should attempt to locate tool marks at the point of entry. In most crimes, a thorough and systematic search for latent fi ngerprints is required. When an investigator fi nds an object of possible evidentiary value, he or she should record its location in notes, sketches, and photographs and then mark its location with an evidence marker (see Figure 3 ).

The search ends when the team or lead investigator determines that all pertinent evidence has been located to the best of the team’s ability. When this determination is made, the team carries out a fi nal survey of the scene. This should include a visual overview of all parts of the scene. Investigators should take an inventory of all evidence collected so nothing is lost or left behind.

wheel/ray search pattern A search method employed by several people who move from the boundary straight toward the center of the scene (inward) or from the center straight to the boundary (outward).

quadrant/zone search pattern A search method in which the crime scene is divided into smaller sections (zones or quadrants) and team members are assigned to search each section. Each of these sections can be subdivided into smaller sections for smaller teams to search thoroughly.

39

SECURING AND SEARCHING THE CRIME SCENE

The team members should be sure to retrieve all equipment. They should also verify that any threats to health or safety at the scene have been or will be dealt with properly. Once all of these measures have been taken, the scene can be released to the proper authorities.

Obviously, the skill of crime-scene investigators at recognizing evidence and searching relevant locations is paramount to successfully processing the crime scene. Although training can impart general knowledge about conduct- ing a proper crime-scene investigation, ultimately the investigator must rely on experience gained from numerous investigations to formulate a successful strategy for recovering relevant physical evidence at crime scenes. If the in- vestigator cannot recognize physical evidence or cannot properly preserve it for laboratory examination, no amount of sophisticated laboratory instrumen- tation or technical expertise can salvage the situation.

The know-how for conducting a proper crime-scene search for physical evidence is not beyond the grasp of any police department, regardless of its size. With proper training, police agencies can ensure they competently pro- cess crime scenes. In many jurisdictions, however, police agencies have del- egated this task to a specialized team of technicians known as crime-scene investigators.

Quick Review • How one carries out a crime-scene search will depend on the locale and

size of the area, as well as on the actions of the suspect(s) and victim(s) at the scene.

• The purpose of the crime-scene search is to locate physical evidence. The particular circumstances of the crime determine what to search for fi rst.

FIGURE 3 Numbered evidence markers are used to show the location of (1) a fi rearm, (2) a beverage can, and (3) another beverage can at a crime scene. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

WebExtra 1

Autopsy of a Murder Search for clues at the scene of a murder. Once you’ve located the relevant evidence, you will need to collect the evidence for laboratory testing. www.mycrimekit.com

40

SECURING AND SEARCHING THE CRIME SCENE

• When evidence is found, the location is documented in notes, photo- graphs, and sketches.

• When the search is deemed complete, the investigating team conducts a fi nal survey that includes a visual overview of all parts of the scene, an inventory of all evidence collected, the retrieval of all equipment, and the neutralization of all health or safety threats. Once all of these measures have been taken, the scene can be released to the proper authorities.

CHAPTER REVIEW

REVIEW QUESTIONS

• The fi rst offi cer arriving on the scene of a crime has the responsibility to preserve and protect the area to the greatest extent possible.

• First priority should be given to obtaining medical assistance for individuals in need of it.

• Steps must be taken by the fi rst responder to exclude all unauthorized personnel from the scene and keep an accurate log of who enters and exits the scene and the time at which they do so.

• The lead investigator is responsible for developing a strategy for the systematic examination and documentation of the entire crime scene.

• The lead investigator must gain an overview of the general setting of the scene. Of particular importance are objects that do not appear to belong or aspects of the scene that may suggest the timing of the incident.

• The presence or absence of evidence may also suggest whether the scene is a primary or secondary scene.

• At the command center, members of the investigative team receive their assignments, store their equipment, congregate to talk about aspects of the case, and communicate with personnel at other crime scenes.

• How one carries out a crime-scene search will depend on the locale and size of the area, as well as on the actions of the suspect(s) and victim(s) at the scene.

• The purpose of the crime-scene search is to locate physical evidence. The particular circumstances of the crime deter- mine what to search for fi rst.

• When evidence is found, the location is documented in notes, photographs, and sketches.

• When the search is deemed complete, the investigating team conducts a fi nal survey that includes a visual overview of all parts of the scene, an inventory of all evidence collected, the retrieval of all equipment, and the neutralization of all health or safety threats. Once all of these measures have been taken, the scene can be released to the proper authorities.

1. True or False: Failure to protect a crime scene properly may result in the destruction or altering of evidence. ______________

2. The ______________ arriving on the scene of a crime is responsible for taking steps to preserve and protect the area to the greatest extent possible, and he or she must rely on his or her training to deal with any violent or hazardous circumstances.

3. At a crime scene, fi rst priority should be given to obtaining ______________ for individuals in need of it and attempting to minimize the disturbance of evidence.

4. All unauthorized personnel must be ______________ from crime scenes.

5. True or False: The boundaries of the crime scene, denoted by crime-scene tape, rope, or traffi c cones, should encompass only the center of the scene where the crime occurred. ______________

6. Even though all unauthorized personnel are not admitted to the scene, a very accurate ______________ must be kept of those who do enter and exit the scene and the time at which they do so.

KEY TERMS

command center

grid search pattern

line/strip search pattern

primary scene

quadrant/zone search pattern

secondary scene

spiral search pattern

walk-through

wheel/ray search pattern

41

APPLICATION AND CRITICAL THINKING

7. True or False: The lead investigator immediately proceeds to gain an overview of the situation and develop a strategy for the systematic examination of the crime scene during the fi nal survey. ______________

8. A(n) ______________ crime scene is one at which the original incident, such as a beating or rape, occurred. A(n) ______________ crime scene became part of the crime as a result of activities that occurred after the initial incident.

9. The investigative team receives assignments, stores equipment, and congregates to talk about aspects of the case at the ______________ .

10. A detailed search of the crime scene must be conducted in a(n) ______________ fashion.

11. The crime-scene search is undertaken to locate _____________ .

12. True or False: The search patterns that may be used to search a crime scene for evidence include the line pattern, grid pattern, polar coordinate pattern, and spiral pattern. ______________

13. When carrying out vehicle searches, investigators must be  careful to avoid contact with surfaces that may contain  ______________ such as steering wheels or door handles.

14. True or False: During nighttime, outdoor scenes should be taped off, left undisturbed, and guarded until daylight. ______________

15. True or False: The search is concluded when the district attor- ney determines that all pertinent evidence has been located to the best of the team’s ability. ______________

16. Once a(n) ______________ of the scene has been carried out, the scene can be released to the proper authorities.

17. True or False: If the investigator does not recognize physi- cal evidence or does not properly preserve it for laboratory examination, sophisticated laboratory instrumentation or technical expertise can salvage the situation and attain the desired results. ______________

1. You are the fi rst offi cer at the scene of an outdoor assault. You fi nd the victim bleeding but conscious, with two of the victim’s friends and several onlookers standing nearby. You call for backup and quickly glance around but see no one fl eeing the scene. Describe the steps you would take while you wait for backup to arrive.

2. What kind of search pattern(s) would investigators be most likely to employ in each of the following situations:

a) Two people searching a small area with well-defi ned boundaries

b) Several people searching a large area

c) A single person searching a large area

3. Offi cer Bill Walter arrives at the scene of an apparent murder: a body bearing several gunshot wounds lies on the fl oor of a small, un-air-conditioned house in late July. A pungent odor almost overwhelms him when he enters the house, so he opens a window to allow him to breathe so he can investigate the scene. While airing out the house, he secures the scene and interviews bystanders. When he inspects the scene, he discovers very little blood in the room and little evidence of a struggle. What mistake did Offi cer Walter make in his investigation? What conclusion did he draw about the scene from his observations?

CASE ANALYSIS

Investigators looking into the kidnapping and murder of DEA spe- cial agent Enrique Camarena and DEA source Alfredo Zavala faced several hurdles that threatened to derail their efforts to collect evidence in the case. These hurdles almost prevented forensics experts from determining the facts of the case and threatened to undermine the investigation of the crime. However, despite these obstacles, use of standard forensic techniques eventually enabled investigators to solve the case. Read about the Camarena case in the following Case Reading, then answer the following questions:

1. What were the main challenges facing investigators who were collecting evidence in the case? Give specifi c examples.

2. Explain how investigators used reference samples to deter- mine that the victims had been held at the residence located at 881 Lope De Vega.

3. Explain how investigators used soil evidence to determine that the victims’ bodies had been buried and later moved to the site where they were discovered.

SECURING AND SEARCHING THE CRIME SCENE

42

SECURING AND SEARCHING THE CRIME SCENE

CASE READING THE ENRIQUE CAMARENA CASE: A FORENSIC NIGHTMARE

MICHAEL P. MALONE

SPECIAL AGENT, LABORATORY DIVISION FEDERAL BUREAU

OF INVESTIGATION, WASHINGTON, D.C.

On February 7, 1985, US Drug Enforcement Agency (DEA) Special Agent (SA) Enrique Camarena was abducted near the US Consulate in Guadalajara, Mexico. A short time later, Capt. Alfredo Zavala, a DEA source, was also abducted from a car near the Guadalajara Airport. These two abductions would trigger a series of events leading to one of the largest investigations ever conducted by the DEA and would result in one of the most extensive cases ever received by the FBI Laboratory . . .

THE ABDUCTION On February 7, 1985, SA Camarena left the DEA resident offi ce to meet his wife for lunch. On this day, a witness observed a man be- ing forced into the rear seat of a light-colored compact car in front of the Camelot Restaurant and provided descriptions of several of the assailants. After some initial reluctance, Primer Comandante Pavon-Reyes of the Mexican Federal Judicial Police (MFJP) was put in charge of the investigation, and Mexican investigators were assigned to the case. Two known drug traffi ckers, Rafael Caro-Quintero and Ernesto Fonseca, were quickly developed as suspects . . .

THE INVESTIGATION During February 1985, searches of several residences and ranches throughout Mexico proved fruitless, despite the efforts of the DEA task force assigned to investigate this matter and the tremendous pressure being applied by the US government to accelerate the investigation. High-level US government offi cials, as well as their Mexican counterparts, were becoming directly involved in the case. It is believed that, because of this “heat,” the Mexican drug traffi ckers and certain Mexican law enforcement offi cials fabricated a plan. According to the plan, the MFJP would receive an anonymous letter indicating that SA Camarena and Captain Zavala were being held at the Bravo drug gang’s ranch in La Angostura, Michoacan, approximately 60 miles southeast of Guadalajara. The MFJP was supposed to raid the ranch, eliminate the drug gang, and eventually discover the bodies of SA Camarena and Captain Zavala buried on the ranch. The DEA would then be notifi ed and the

Undated photo of Enrique Camarena. AP Wide World Photos Reprinted in part from FBI Law Enforcement Bulletin, September 1989.

case would be closed. Thus, the Bravo gang would make an easy scapegoat.

During early March, MFJP offi cers raided the Bravo ranch before the DEA agents arrived. In the resulting shootout, all of the gang members, as well as one MFJP offi cer, were killed. However, due to a mix-up, the bodies of SA Camarena and Captain Zavala were not buried on the Bravo ranch in time to be discovered as planned. Shortly after this shootout, a passerby on a road near the Bravo ranch found two partially decomposed bodies wrapped in plastic bags. The bodies were removed and transported to a local morgue, where they were autopsied. The DEA was then advised of the discovery of the bodies and their subsequent removal to another morgue in Guadalajara, where a second autopsy was performed.

Cadaver number 1 was quickly identifi ed by the fi ngerprint expert as SA Camarena. Although Mexican offi cials would not allow the second body to be identifi ed at this time, it was later identifi ed through dental records as Captain Zavala.

43

SECURING AND SEARCHING THE CRIME SCENE

The FBI forensic team requested permission to process the clothing, cordage, and burial sheet found with the bodies, but the request was denied. However, they were allowed to cut small, “known” samples from these items and obtain hair samples from both bodies. Soil samples were also removed from the bodies and the clothing items. FBI and DEA personnel proceeded to the Bravo ranch, where the bodies were initially found. Because this site had been a completely uncontrolled crime scene, contaminated by both police personnel and onlook- ers, only a limited crime scene search was conducted. It was immediately noted that there was no gravesite in the area and that the color of the soil where the bodies had been deposited differed from the soil that had been removed from the bodies. Therefore, “known” soil samples from the drop site were taken to compare with soil removed from the victims. It was also noted that there were no signifi cant body fl uids at the “burial” site. This led the forensic team to conclude that the bodies had been buried elsewhere, exhumed, and transported to this site.

In late March 1985, DEA agents located a black Mercury Grand Marquis that they believed was used in the kidnapping or transportation of SA Camarena. The vehicle had been stored in a garage in Guadalajara, and a brick wall had been constructed at the entrance to conceal it. The vehicle was traced to a Ford dealership owned by Caro-Quintero. Under the watchful eye of the MFJP at the Guadalajara Airport, the FBI forensic team processed the vehicle for any hair, fi ber, blood, and/or fi ngerprint evidence it might contain.

During April 1985, the MFJP informed the DEA that they believed they had located the residence where SA Camarena and Captain Zavala had been held. The FBI forensic team was immediately dispatched to Guadalajara; however, they were not allowed to proceed to the residence, located at 881 Lope De Vega, until an MFJP forensic team had processed the residence and had removed all of the obvious evidence.

On the fi rst day after their arrival, the FBI forensic team surveyed and began a crime-scene search of the residence and surrounding grounds (see Figure 1 ). The residence consisted of a large, two-story structure with a swimming pool, covered patio, aviary, and tennis court surrounded by a common wall. The most logical place to hold a prisoner at this location would be in the small outbuilding located to the rear of the main residence. This outbuilding, designated as the “guest house” by investigators, consisted of a small room with a beige rug and an adjoining bathroom. The entire room and bathroom were processed for hairs, fi bers, and latent fi ngerprints. The single door into this room was made of steel and reinforced by iron bars. It was ulti- mately determined by means of testimony and forensic evidence that several individuals interrogated and tortured SA Camarena

in this room. In addition, a locked bedroom, located on the sec- ond fl oor of the main house, was also processed, and the bed linens were removed from a single bed. Known carpet samples were taken from every room in the residence.

A beige Volkswagen Atlantic parked under a carport at the rear of the residence fi t the general description of the smaller ve- hicle noted by the witness to SA Camarena’s abduction. The VW Atlantic was also processed for hairs, fi bers, and fi ngerprints.

On the second day, a thorough grounds search was con- ducted. As FBI forensic team members were walking around the tennis court, they caught a glimpse of something blue in one of the drains. On closer inspection, there appeared to be a folded license plate at the bottom of the drain. The license plate was retrieved, unfolded, and photographed. The MFJP offi cers, all of whom were now at the tennis court, became upset at this discovery, and one of them immediately contacted his superior at MFJP headquarters, who ordered them to secure the license plate until the assistant primer comandante arrived on the scene. Upon his arrival approximately 20 minutes later, he seized the license plate and would not allow the Americans to conduct any further searches.

In September 1985, DEA personnel went to La Primavera Park and recovered a soil sample. This sample matched the soil samples from SA Camarena and Captain Zavala’s cadavers al- most grain for grain, which indicated that this site was almost certainly their burial site before they were relocated to the Bravo ranch.

Later that fall, after further negotiations between the US and the Mexican governments, permission was fi nally granted for an FBI forensic team to process the evidence seized by the MFJP forensic team from 881 Lope De Vega the previous April. The evidence consisted of small samples the MFJP had taken of SA Camarena’s burial sheet, a piece of rope used to bind SA Camarena, a portion of a pillowcase removed from bedroom number 3, a piece of unsoiled rope removed from the covered patio, and a laboratory report prepared by the MFJP Crime Laboratory. The remainder of the evidence had been destroyed for “health reasons.”

In January 1986, a drug traffi cker named Rene Verdugo, who was considered to be a high-ranking member of the Caro-Quintero gang, was apprehended and taken to San Diego, where he was arrested by the DEA. He was then transported to Washington, D.C., where samples of his hair were taken. He refused to testify before the federal grand jury investigating the Camarena case. Later that year, DEA personnel obtained hair samples in Mexico City from Sergio Espino-Verdin, a former fed- eral comandante who is believed to have been SA Camarena’s primary interrogator during his ordeal at 881 Lope De Vega.

44

SECURING AND SEARCHING THE CRIME SCENE

Sliding Gate

Tennis Court

License Plates Found

BATHHOUSE & SPA

AVIARY

PRIVATE BUSINESS

WALL

Covered Porch

SIDE ENTRANCE

VW ATLANTICGROUNDS

WALL AND ARCHWAYS

SIDE ENTRANCEC

ov er

ed P

at io

s

Swimming Pool

Storage

GUEST ROOM

MAID’S ROOM

BA TH

Storage

KITCHEN MAIN HOUSE

FRONT PORCH

Co ve

re d

Po rc

h

LI VI

N G

-D IN

IN G

RO O

M

B ED

RO O

M S

LIBRARY

GARAGE Area

FIGURE 1 A diagram of the 881 Lope De Vega grounds. Camarena was held prisoner in the guest house. FBI Law Enforcement Bulletin, September, 1989.

THE TRIAL In July 1988, the main trial for the murder, interrogation, and abduction of SA Camarena began in US District Court in Los Angeles, California. The forensic evidence presented in this trial identifi ed 881 Lope De Vega as the site where SA Camarena had been held. The evidence also strongly associated two

Mexican citizens, Rene Verdugo and Sergio Espino-Verdin, with the “guest house” at 881 Lope De Vega. Several types of forensic evidence were used to associate SA Camarena with 881 Lope De Vega: forcibly removed head hairs found in the “guest house” and bedroom number 4, in the VW Atlantic, and in the Mercury Grand Marquis, and two types of polyester rug

45

SECURING AND SEARCHING THE CRIME SCENE

FIGURE 2 A trial chart showing hair comparisons between known Camarena hairs and hairs recovered from 881 Lope De Vega. FBI Law Enforcement Bulletin, September, 1989.

46

SECURING AND SEARCHING THE CRIME SCENE

FIGURE 3 A trial chart showing hair comparisons between known Camarena hairs and hairs recovered from the Mercury Grand Marquis. FBI Law Enforcement Bulletin, September, 1989.

47

SECURING AND SEARCHING THE CRIME SCENE

fi bers: a dark, rose-colored fi ber and a light-colored fi ber (see Figures 2 and  3 ). Fabric evidence was also presented, which demonstrated the similarities of color, composition, construc- tion, and design between SA Camarena’s burial sheet and the two pillowcases recovered from bedrooms number 3 and 5.

Based on this evidence associating SA Camarena and 881 Lope De Vega, the FBI Laboratory examiner was able to testify that SA Camarena was at this residence, as well as in the VW Atlantic and the Mercury Grand Marquis, and that he had been in a position such that his head hairs were forcibly removed. Captain Alfredo Zavala was also found to be associated with the “guest house” at 881 Lope De Vega. Light-colored nylon rug fi bers found on samples of his clothing taken at the second autopsy matched the fi bers from the “guest house” carpet.

A detailed model of the residence at 881 Lope De Vega was prepared by the Special Projects Section of the FBI Laboratory for the trial (see Figure 4 ). Over twenty trial charts were also prepared to explain the various types of forensic evidence. These charts proved invaluable in clarifying the complicated techniques and characteristics used in the examination of the hair, fi ber, fabric, and cordage evidence (see Figure 5 ).

CONCLUSION After an eight-week trial, conducted under tight security and in- volving hundreds of witnesses, all of the defendants were found guilty and convicted on all counts, and are currently serving lengthy sentences.

FIGURE 4 A model of 881 Lope De Vega prepared as a trial exhibit. FBI Law Enforcement Bulletin, September, 1989.

48

SECURING AND SEARCHING THE CRIME SCENE

FIGURE 5 A trial chart used to show the association of Camarena and Zavala with various locations. FBI Law Enforcement Bulletin, September, 1989.

Mercury CamarenaHead Hair Blood on Floor Mat

VW Atlantic

Camarena Head Hair

Blood on Tissue

Guest House

Camarena Head Hair

Zavala Clothes

Nylon

Bedroom #3

Camarena Blindfold Polyester

Pillow Case Camarena

Burial Sheet

Bedroom #4

Camarena Head Hair

Camarena Blindfold & Burial Sheet

Polyester

Bedroom #5

Pillow Case Camarena

Burial Sheet

Tennis Court

License Plate

VW/Merc.

Camarena Burial Sheet

Camarena Head Hair

Bedroom #4 Polyester

Pillow Case Bedrooms #3 and #5

Soil La

Primavera

Source — Blindfold/

Rope

Camarena Head Hair

Bedrooms #3 and #4 Polyester

Camarena Blindfold

Tape

Camarena Burial

Cordage

Burial Rope from Covered

Patio

Zavala Clothing

Zavala Head Hair

Guest House Nylon

Soil La

Primavera

CATEGORIES OF FORENSIC EVIDENCE IN CAMARENA CASE

TYPE OF EVIDENCE

Carpet Fibers

Fabric Match

Cordage Match

Tape MatchLOCATION Hair Misc.

49

50

Recording the Crime

Scene

From Chapter 3 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

THE LINDBERGH BABY CASE On the evening of March 1, 1932, a kidnapper crept up his homemade ladder and stole the baby of Charles and Anne Lindbergh directly from the second-fl oor nursery of their house in Hopewell, New Jersey. The only evidence of his coming was a ransom note, the ladder, a chisel, and the tragic absence of the infant. Although the $50,000 ransom had been paid, the baby turned up dead in the woods a mile away a couple of months later. There was no additional sign of the killer. Fortunately, when it was fi nally studied by wood technologist Arthur Koehler, the

abandoned ladder yielded some impor- tant investigative clues.

By studying the types of wood used and the cutter marks on the wood, Koehler ascertained where the materials might have come from and what specifi c equip- ment was used to create them. Koehler traced the wood from a South Carolina mill to a lumberyard in the Bronx, New York. Unfortunately, the trail went cold because the lumberyard did not keep sales records. The break in the case came in 1934, when Bruno Richard Hauptmann paid for gasoline with a bill that matched a serial number on the ransom money. Koehler was able to show that micro- scopic markings on the wood were made by a tool in Hauptmann’s possession. A ladder rail recovered from the home- made ladder had characteristics consis-

tent with wood present in Hauptmann’s attic. Ultimately, handwriting analysis of the ransom note clearly showed it to have been written by Hauptmann.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Explain the steps to be taken to fully record the crime scene. • Describe the proper format and content of crime-scene notes. • Understand the basic features of fi lm and digital cameras in

order to produce examination-quality photographs. • Describe the process and importance of creating a rough and

a fi nished crime-scene sketch.

Recording the Crime

Scene

New York Daily News Archive via Getty Images New York Dailyy News Archive via Getty Iy magges

52

RECORDING THE CRIME SCENE

I nvestigators have only a limited amount of time to work a crime site in its untouched state. They must not lose the opportunity to permanently record the scene in its original condition. Such records not only will prove useful

during the subsequent investigation but also must be presented at a trial in or- der to document the condition of the crime scene and the location of physical evidence. Notes, photographs, and sketches are the three methods of crime- scene recording (see Figure 1 ).

Notes The note-taking process begins with the call to a crime-scene investigator to report to a scene. The fi rst notes should identify the person who contacted the investigator and record the time of the contact and any preliminary informa- tion disclosed, including the case number. When the lead investigator arrives, the note taker should record the date and time of arrival, who is present, and the identities of any other personnel who are being contacted. If additional personnel are contacted, their names, titles, and times of arrival should be recorded.

A crime scene should be off-limits to any people who are not directly in- volved with the processing. Investigators must keep very precise records of personnel movements in and out of the scene, beginning with the movements of the fi rst responding offi cer. It is also important to record the tasks assigned to each member of a team, as well as the beginning and ending times of the processing of the scene.

Before the scene is sketched, photographed, or searched, the lead inves- tigator carries out the initial walk-through. During this walk-through, the in- vestigator should take notes on many aspects of the crime scene in its original condition. Notes taken by an investigator should be uniform in format for all

FIGURE 1 The fi nding of an evidential cigarette butt at the crime scene requires photographing it, making a sketch showing its relation to the crime scene, and recording the fi nd in notes. Courtesy Police Science Ser- vices, Niles, IL

53

RECORDING THE CRIME SCENE

cases. The notes should be in ink (preferably black or blue) and written in a bound notebook. Most important, notes should be written at the time of the crime-scene investigation, not left to record from memory at a later time. At this time, the investigator may need to interview the fi rst responding offi cer. The offi cer should supply information on any events at the crime scene that the offi cer or others witnessed. When the walk-through is complete, the lead investigator assigns specifi c tasks or areas to members of the crime-scene team. The notes should also record these assignments, as well as the times at which each task was started and completed.

Once a search for evidence has taken place, the team members mark the location of all evidence. The investigator should note whether any evidence was disturbed by emergency medical personnel, a suspect, or investigative personnel. Before the team collects items of evidence, the investigator must fully describe each item in his or her notes. The person who collects a piece of evidence should note who found it, where it was located, how it was pack- aged, who packaged it, and when it was packaged. The notes should also men- tion whether the evidence underwent any fi eld tests or processing.

If a victim is present at a homicide scene, the investigator should observe and record the state of the body before the medical examiner or coroner moves it. The notes should describe the victim’s appearance and record the position of the body and any visible wounds or blood spatter. The investigator should make note of any identifying features or marks on the body, such as tattoos. He or she should also make a list of objects found on the body, such as a wallet or jewelry, before collecting those items. Moving the body may reveal previously unseen injuries and physical evidence that the investigator should record. The notes should indicate when the medical examiner or coro- ner moved the body and whether the victim was moved or affected in some way by emergency medical procedures. Any preliminary identifi cation of a victim or suspect should be recorded.

Audio recording of notes at a scene can be advantageous because detailed notes can be spoken much faster than they can be written. This may also leave the investigators’ hands free to carry out other tasks while recording the notes. However, care must be taken to avoid embarrassing conversation on tapes that will be used as evidence in a trial. Some investigators may use digital voice recorders to record their notes. These recordings are easily uploaded to a computer, but they must be copied to a disk to produce a hard copy. Another method of recording notes is by narrating a digital video of the crime scene. This has the advantage of combining note taking with photography. However, at some point the tape must be transcribed into a written document.

The note taker must keep in mind that this written record may be his or her only way of refreshing his or her memory months, perhaps years, after a crime has been processed. The notes must be suffi ciently detailed to anticipate this need.

Quick Review • Because investigators have only a limited amount of time to work a crime

site in its untouched state, the opportunity must not be lost. • Crime-scene notes should include contact information, personnel infor-

mation and movements, task assignments, observations of the victim and scene, and information about the evidence before and after it is processed.

• Recording notes on digital voice recorders is advantageous, but in- vestigators should take care to speak clearly and avoid including side conversations.

54

RECORDING THE CRIME SCENE

Photography All jurisdictions commonly accept photographs of crime scenes as visual evi- dence in criminal investigations. Investigators should therefore understand the procedures and principles of good crime-scene photography in order to best illustrate aspects of the scene. The goal of photography at crime scenes is to produce examination-quality photographs. This means that everyone in- volved in the case, from the investigators to the judge and jury, must be able to interpret the photographs easily.

Crime-scene photographs can show the layout of the scene, the posi- tion of evidence to be collected, and the physical relationship of objects at the scene to one another. Photographs taken from many angles can show possible lines of sight of victims, suspects, and witnesses. Photography is also important for documenting biological evidence in its original condi- tion because this kind of evidence is often altered during testing. Photo- graphs cannot stand alone, however; they are complementary to notes and sketches.

FILM AND DIGITAL PHOTOGRAPHY

Currently there are two methods or approaches to crime-scene photography: fi lm and digital photography . The differences between the two relate to the ways they convert light into images.

FILM Photographic film consists of a sheet of light-reactive silver halide grains and comes in several varieties. Print film produces a negative im- age that is developed to produce a positive image. Slide film, by contrast, produces positive images on transparent slides used for presentation. A special type of infrared film produces images when exposed to infrared light.

Film also comes in a variety of sizes. The most common fi lm size for still photography in modern times is 135, commonly known as 35 mm. The image area on this type of fi lm is 24 by 36 millimeters. The next size up is known as medium format or 120 fi lm. The 120 fi lm is 60 millimeters wide, and the image can be 45 or 60 millimeters in length. Medium or large prints can be made on sheet fi lm instead of rolled fi lm. Sheet fi lm commonly measures 4 by 5 inches.

Film speed determines how sharp or grainy a photograph looks. The fi lm speed is the rate at which the fi lm reacts with light. High-speed fi lms contain larger grains of silver that react more quickly with light, making them ideal for scenes in which light is at a minimum. High-speed fi lms, however, produce grainier pictures than lower-speed fi lms. Lower-speed fi lms produce sharper photographs, but they require more light to react with the smaller grains. Film speed is measured by two different scales. The International Standardization Organization (ISO) scale is simply arithmetic: ISO 200 fi lm has twice the speed of ISO 100 fi lm. The German Institution for Standardization (DIN) uses a loga- rithmic scale in which a three-unit increase is equal to twice the speed. Thus, DIN 28 fi lm is twice the speed of DIN 25 fi lm.

Infrared fi lm records only images that refl ect infrared light. Because some inks refl ect infrared light, this type of fi lm is frequently used in questioned- document examination to view text that has been crossed out or altered. It is also useful for locating grave sites in aerial photography, visualizing gunshot residue on dark fabrics, and viewing underlying patterns in bite and bruise

digital photography The use of electronic means to capture light and save an image on a microchip.

fi lm speed The rate at which the silver halide grains of a given fi lm react to light.

55

RECORDING THE CRIME SCENE

marks. Many cameras have separate settings for infrared fi lm. Infrared fi lm should not be stored for long periods of time because it will deteriorate.

DIGITAL IMAGE RECORDING A digital photograph is made when a light- sensitive microchip inside a digital camera is exposed to light coming from an object or scene. A digital camera captures light on each of millions of tiny picture elements called pixels. The light is recorded on each pixel as a spe- cifi c electric charge using a charged coupled device (CCD) or complementary metal oxide semi-conductor (CMOS). The camera reads this charge number as image information, then stores the image as a fi le on a memory card.

The number of pixels used to capture light is directly related to the resolu- tion of the picture. Resolution is defi ned as the minimum distance that must separate two objects in order for them to be viewed as distinct objects. The lower the distance needed, the greater the resolution of the photograph. Pho- tographs of increasingly higher resolution show more and more detail and sharpness. The greater the number of pixels featured on the digital camera, the better the resolution will be.

Because the number of pixels on a digital camera is in the millions, it is usually referred to in terms of megapixels . A camera that has four million pix- els is a four-megapixel camera. A standard four-megapixel camera can create a clear image on a photographic print of up to 8 by 10 inches. As the number of megapixels increases, the clarity increases, allowing photographers to cre- ate bigger prints. Crime-scene photographers usually use cameras that fea- ture as many as ten megapixels or more.

PHOTOGRAPHIC EQUIPMENT

AND PRINCIPLES

Whether they employ fi lm or digital methods, photographers must master the same basic methods and use many of the same kinds of specialized equipment.

The cameras, lenses, fl ashes, and fi lters used in digi- tal and fi lm photography perform the same functions and operate on the same set of principles.

CAMERAS The most commonly used camera for fi lm crime-scene photography is the single lens refl ex camera , or SLR. The digital version of this camera is called a digital single lens refl ex, or DSLR (see Figure  2 ). Although digital imaging technology is becoming dominant in all aspects of photography, many jurisdictions still advocate the use of fi lm or a combination of fi lm and digital.

Although the general public is more familiar with digital “point and shoot” cameras, SLR and DSLR cam- eras are required for photographing a crime scene. Both kinds of SLR cameras allow for the use of a wide range of lenses, fl ashes, and fi lters. Further, SLR and DSLR cameras give photographers the option of man- ually selecting f-stop, shutter speed, and other vari- ables associated with photography. These settings are discussed in further detail in the following sections. DSLRs also have a large imaging microchip that pro- duces higher-quality images and prints than the tradi- tional “point and shoot” digital cameras can produce.

LENSES The lens of the camera is the mechanism that bends light to focus an image on the fi lm or digital microchip. In general, the thicker the lens,

megapixel One million pixels; used to describe a digital camera in terms of sensor resolution (i.e., four megapixels equals four million pixels).

FIGURE 2 An example of a digi- tal single lens refl ex (DSLR) camera. WHITERABBIT83/shutterstock.com

single lens refl ex (SLR or DSLR) camera A type of camera that uses the same lens for viewing and for taking the picture. The image seen in the viewfi nder or on the LCD monitor is how the photo will turn out.

56

RECORDING THE CRIME SCENE

the greater its ability to bend light. Each lens has a specifi c focal length, which is the distance between the lens and the image projected on the fi lm or microchip. As the thickness and bending ability of the lens increases, the focal length decreases because the lens can bend light onto a surface closer to it. Photographers generally use lenses with long focal lengths to capture in more detail objects far from the camera. The kind of lens one uses, therefore, has a great impact on the quality of the photographs a camera produces.

Normal Lens The normal lens has a 50 to 55 mm focal length. It can be used for most photographs that need to be taken at a crime scene because it can capture as much area as half a wall. It can also take satisfactory photo- graphs of pieces of evidence at standard distances.

Telephoto Lens The telephoto lens is like a telescope attachment for the cam- era, capturing a close-up image of a distant object or subject. This lens has a focal length of 100 mm or greater. This means that a 200 mm telephoto lens, for example, produces an image that is four times the magnifi cation of the normal 50 mm lens.

Wide-Angle Lens A photographer who needs to capture a wider area uses a wide-angle lens with a focal length of less than 50 mm. The typical focal length of the wide-angle lens is 35 mm, and it can show much more area in one photograph than can a normal lens. For example, this lens is use- ful in photographing wide objects such as the facade of a building; it will capture more detail to the left and right of the center of the structure than will a normal lens.

Macro Lens When very close photographs and good detail are required, the photographer might use a macro lens. The macro lens has a focal length of less than 50 mm and a 1:1 or 1:2 magnifi cation ratio. It is especially useful for close-ups of fi ber or tool mark evidence.

Multipurpose Lens A multipurpose lens, commonly called a zoom lens, can also be used for crime-scene photography. These lenses have a range of focal lengths, usually from 28 to 80 mm. This type of lens allows the pho- tographer to take normal, wide-angle, and telephoto photographs without changing lenses.

Most DSLR cameras have a fi xed normal or multipurpose lens, typically in the range of 14 to 55 mm, and accept a variety of other lenses. Some digital cameras have specifi c settings to mimic the effects of special lenses. For ex- ample, the macro setting on a digital camera, usually represented by a fl ower symbol, offers the attributes of a macro lens by making the foreground appear larger and the background appear smaller.

APERTURE AND SHUTTER SPEED The amount of light gathered by the cam- era is regulated by the aperture and shutter speed of the camera. The camera aperture is the diameter of the opening of the mechanism, called the diaphragm, which allows in light. On fi lm or digital cameras, one adjusts the aperture by setting the f-number, which is equal to the focal length of the lens divided by the diameter of the aperture. Thus, the f-number and aperture are inversely re- lated. The lower the f-number setting, the wider the aperture and the more light it allows in. Standard f-number settings have come to be known as f-stops , ranging along a continuum of possible aperture sizes. For example, the lowest f-number (1.0) is arbitrarily designated as f-stop zero (f-0). Each f-stop repre- sents a twofold difference in the amount of light entering the camera. Because f-stop and aperture are inversely related, f-2 thus would have a larger aperture than f-22. Some fi lm and digital cameras, called aperture priority cameras, allow the user to control the f-stop manually, but not the shutter speed.

The shutter of a camera is the mechanism that controls the exposure of the fi lm or microchip to light. The shutter speed is the length of time that the

aperture The size of the diaphragm opening through which light enters the camera.

f-stop A setting on a camera that controls the aperture diameter to determine the amount of light transmitted through the lens to the fi lm or microchip.

shutter speed The length of time that the fi lm or microchip is exposed to light.

57

RECORDING THE CRIME SCENE

fi lm or microchip is exposed to light. This is measured in fractions of a second by factors of 1/2 (i.e., 1/2, 1/4, 1/8, etc.). A fi lm camera that allows the user to manually change the shutter speed shows only the bottom number. On these cameras, the optimal setting is usually marked in red.

DSLR cameras have a wide range of options for adjusting f-stop and shut- ter speed. The green “auto” mode automatically selects an appropriate f-stop and shutter speed for the conditions. Alternately, digital cameras may have a setting known as “sports mode” to capture subjects in motion by using a higher (faster) shutter speed. This setting is usually represented by a symbol of a fi gure running or a foot kicking a ball. A digital camera’s “night mode,” denoted by a moon or star, is set for a lower (slower) shutter speed. This al- lows the shutter to be open longer to gather as much light as possible to create the image. SLR and DSLR cameras allow the user to change shutter speed by adjusting a control knob on the camera. Also, the photographer can operate the camera in a fully manual mode.

DEPTH OF FIELD An important trait of a photograph is the depth of fi eld shown. This is the amount of area in the foreground and background of an in-focus object that is also relatively in focus. This is especially important in photographs of an entire scene and of three-dimensional objects. The smaller the aperture is, the greater the depth of fi eld will be. It is important to remem- ber that the aperture is measured on a camera by the f-stop number, which is inversely related to the aperture diameter. This means that higher f-stops will yield higher depths of fi eld. The “landscape mode” on a digital camera (gener- ally represented by a mountain symbol) automatically selects higher f-stops to improve the depth of fi eld when the background and foreground are impor- tant, such as in scenery photographs. The “portrait mode” of a digital camera, on the other hand, selects lower f-stops to decrease the depth of fi eld and make the subject stand out clearly against a blurred background.

ILLUMINATION Illumination refers to the light falling on an object in a pho- tograph. An important photographic aspect of light is its color temperature . This is the measurement of the difference in hue between a light source and a theoretical source of perfect white light. On the color temperature scale, a “hot” light source has a bluer hue, whereas a “cold” light source has a red- orange hue. Different light sources exhibit different color temperatures. Simi- larly, sunlight will exhibit varying color temperatures during different times of the day and in different weather conditions.

Film cameras will detect or even exaggerate the color of the light source, making the scene appear different on fi lm than it appears to the naked eye. Specifi c fi lm should be purchased for use under certain light conditions. For example, tungsten fi lm is best suited for use under incandescent indoor light- ing, whereas daylight fi lm is better for use in sunlight. Most digital cameras have automatic “white balance” settings that allow them to automatically com- pensate for color temperatures that deviate from white. Some digital cameras feature additional white balance modes for specifi c light sources, including in- candescent lighting, fl uorescent lighting, direct sunlight, and overcast sunlight.

Manipulating Illumination A photographer must be able to recognize and manipulate the amount of light and the angle of illumination in a photograph. Light meters are devices that allow photographers to measure the amount of light in a shot. An incident light meter in a fi lm camera measures the amount of light being projected onto a photographic subject regardless of whether the surface is refl ective (white) or nonrefl ective (black). A refl ective light meter in a fi lm camera measures the amount of light refl ected off photographic sub- jects. For a picture that is neither too dark nor too light, a surface that refl ects 18 percent of the light (gray colored) is recommended. Film photographers

depth of fi eld The amount of area in the foreground and background of an in-focus photographic subject that is also relatively in focus.

color temperature The measure of the “degree of whiteness” of a light source compared to a hypothetical source of perfect white light.

58

RECORDING THE CRIME SCENE

can also manipulate the angle of illumination by using a movable light source such as a fl ash on a stretchable cord. Sometimes direct light at 90 degrees to the subject is acceptable. However, in the case of three-dimensional objects that need to display depth, light from oblique angles (commonly 30 degrees or 60 degrees) can be used to cause shadows that show depth. This technique is especially helpful for illuminating impressions from footwear and tires.

Most digital cameras also have light meters, but the user may have to choose a function from the menu to activate the light meter. Digital cameras designed for the casual user rely on preprogrammed settings and computer technology to determine the optimal settings (such as shutter speed and f-stop) for each photograph taken. In place of manual f-stop operation, a digital camera may use exposure compensation that the user can adjust to capture an extremely bright or dark image. Most digital cameras offer the values �2, �1, 0, 1, and 2. The “0” setting refers to the starting point—that is, the conditions the camera’s autofocus feature determines to be optimal. Adjusting toward negative numbers will reduce the exposure, thereby dark- ening a bright (overexposed) shot.

To compensate for backlighting, a camera may have a center-weighted or spot metering setting. Center-weighted metering directs the camera to deter- mine the optimal settings based on the light conditions present in the center of the fi eld. Spot metering directs the camera to calculate the best settings for the light conditions at the spot on the center of the viewfi nder. The default setting, called matrix or evaluative metering, is based on the average light intensity across the entire fi eld of view. Some manufacturers have preprogrammed set- tings named for specifi c light conditions and composition. Some of the more expensive digital cameras show a graph of the light present in the photograph to help suggest exposure settings.

Flashes The electronic strobe fl ash is the most commonly used source of artifi cial illumination in photography. This type of fl ash is usually mounted on the top or front of a camera. A fl ash unit is an electronic fl ash that is not mounted to the camera. It is either separately operated or connected to the camera by a cord. In either case, the user must time the fl ash with the cor- rect shutter speed for fl ash photography (usually 1/60). The fl ash unit, also called a slave fl ash, is very important to crime-scene photography because it can illuminate dark areas or create lighting at various angles to show greater detail.

A fl ash can produce direct refl ective, direct, and oblique lighting, de- pending on the photographer’s needs. Direct refl ective lighting occurs when the fl ash is attached to the camera or placed at 90 degrees to the plane of view. It provides high contrast, but may show light refl ectance in the photograph. Direct lighting is aimed 45 degrees to the plane of view to minimize refl ectance. Oblique lighting involves placing the fl ash at an angle to the plane of view that is lower than 45 degrees to show greater detail by creating a shadowing effect. Regardless of what kind of fl ash is used, it may be necessary to manually increase or decrease the fl ash power. For example, decreasing the fl ash power can help avoid overexposing a close subject.

Most commercially available digital cameras have mounted electronic strobe fl ashes. This integrated fl ash can illuminate subjects only up to ten feet away. Many digital cameras have a fl ash bracket for using a supplementary fl ash when one is necessary. Digital cameras also have a feature called “fi ll fl ash.” This narrows the range of the fl ash to concentrate illumination on only a dark, backlit subject or object. This is used to eliminate undesirable shadows that may obscure the subject. Fill fl ash can be used to eliminate shadows un- der trees and vehicles.

59

RECORDING THE CRIME SCENE

Because mounted fl ashes on fi lm and digital cameras illuminate only a spe- cifi c distance, a photographer may have to use refl ectors to direct light to il- luminate specifi c objects.

Filters The use of fi lters in photography can help enhance specifi c elements of a picture or show elements of the picture that are not usually visible. Filters allow only specifi c wavelengths (colors) of light to reach the fi lm.

The most common types of fi lters are barrier and bypass fi lters. Barrier fi lters block one specifi c wavelength of light (i.e., color) from reaching the fi lm or microchip, making areas of that color appear lighter in the photo- graph. This is helpful when a fi ngerprint or other feature on a piece of evi- dence is diffi cult to see against a surface of a specifi c color. A bypass fi lter allows only a small range of wavelengths of light to reach the fi lm or micro- chip, and blocks all others. Ultraviolet photography uses a bypass fi lter that allows only ultraviolet light to reach black-and-white fi lm. Objects that fl uo- resce, or glow, under ultraviolet light—such as semen, components of some fi bers, and fl uorescent fi ngerprint powder—appear more readily using this technique. It is also sometimes used when photographing wounds to show greater contrast.

By using a fi lter of a complementary color, a photographer can make cer- tain areas of an object appear darker. A red fi lter, for example, will darken blue/green areas, and an orange/yellow fi lter will darken blue/ violet areas. A polarizer fi lter may be used to eliminate refl ections from windows and water and to eliminate glare. A photographer may also employ a fi lter when the light source used at the scene is a laser.

TRIPODS The use of a tripod can improve the quality of a photograph by eliminating the possibility of blurred photos resulting from unsteady hands. Any photograph taken at a shutter speed of less than 60 (1/60 second) must

be taken from a tripod. A tripod with independently adjustable legs is a superior choice because it is suit- able for uneven terrain. The tripod should also have a bubble level on it to help ensure 90-degree images of evidence (see Figure 3 ).

FIGURE 3 A tripod used for crime-scene photography should have adjustable legs that are sturdy to ensure 90-degree photographs. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

Quick Review • Film is made of a sheet of light-reactive silver ha-

lide grains. The light-capturing ability of the grains is called fi lm speed, and higher-speed fi lms have bigger grains in order to capture light faster. This means that higher-speed fi lms create grainier pho- tographs.

• Digital cameras feature a light-sensitive microchip that captures light on each of millions of tiny pic- ture elements, called pixels. The light is recorded on each pixel as a specifi c charge that will later be electronically translated to an image. The number of pixels on a camera is measured in the millions, called megapixels, and directly affects an image’s resolution.

• SLR and DSLR cameras allow for the use of a wide range of lenses, including normal lenses, telephoto lenses, wide-angle lenses, macro lenses, and multi- purpose lenses. The kind of lens used affects the appearance of the image.

• The aperture and shutter speed regulate the amount of light gathered by the camera. These settings can be manually adjusted on SLR and DSLR cameras.

60

RECORDING THE CRIME SCENE

• The f-stop determines depth of fi eld, or the amount of area in the fore- ground and background that is in focus. The higher the f-stop, the smaller the aperture and the greater the depth of fi eld. Landscape and portrait set- tings on a digital camera adjust for higher and lower f-stops, respectively.

• The color temperature of the light source used will make a photographic image appear orangish or bluish. Many digital cameras combat this with “white balance” capability. Exposure compensation and electronic fl ashes can be used to capture images of dark or light subjects. Flash units, or slave fl ashes, are helpful to provide oblique or versatile illumination.

• Filters are used with SLR or DSLR cameras to block certain wavelengths of light (barrier fi lters) or allow in only certain wavelengths of light (by- pass fi lters). Filters can be used to show greater detail in photographs by adjusting the appearance of specifi c colors.

• Tripods can greatly improve photograph quality by preventing blurri- ness caused by the movement of the photographer’s hand. They also help ensure 90-degree close-up photographs of evidence.

Crime-Scene Photography

BASIC GUIDELINES

Photograph the crime scene in an unaltered condition Except for injured parties, subjects and objects must not be moved until they have been pho- tographed from all necessary angles. If objects are removed, positions changed, or items added, the photographs may not be admissible as evi- dence at a trial. In that case, their intended value will be lost. Evidence should not be reintroduced into the scene in order to take photographs. If a body is found at the crime scene, it should be photographed before it is moved. The body must be photographed at various angles so the body’s position is well documented.

Fill the frame The object being photographed should not be diffi cult to dis- tinguish from a background that is not vital to the overall image. Filling the frame may require physically moving the camera closer to the subject and into a position that does not show undesirable objects in view. Sometimes important details can be gathered from photographing down on the sub- ject’s level. These details might not otherwise be apparent.

Avoid shadows in the photograph A photographer might not think to use a fl ash when outdoors. However, doing so can help fi ll in shadows.

Maximize depth of fi eld A crime scene’s depth of fi eld can be very small or very large. In either case, it is important to have all items of signifi cance in focus.

Photograph the scene in a logical sequence This means that the crime scene should include the area in which the crime actually took place and all adjacent areas where important acts occurred immediately before or after the commission of the crime. The photographer commonly will work from the perimeter to the center of a scene. The sequence used must be kept consistent for all crime scenes. This will show the overall scene fi rst, then work down to individual pieces of evidence so that jurors in the trial can easily relate them back to the larger scene (see Figure 4 ).

Keep a log The fi rst picture on each roll of fi lm taken at the crime scene should show the photography log form; likewise, the photo log should be recorded as the fi rst image of the series if a digital camera is used. The top of the photography log form should include the case number, the type of scene, the date, the location of the scene, a description of the camera

photography log The form on which the investigator records the details of each photograph taken at a crime scene.

61

RECORDING THE CRIME SCENE

(b)

FIGURE 4 This sequence of crime-scene photographs shows the proper progression of photographing the scene. (a) The sequence be- gins with an overview photograph of the entry to the victim’s bedroom showing evidence markers in place. (b) The medium-range photograph shows the evidence marker next to the door denoting a cartridge case. (c) The close-up photograph shows the cartridge in detail with a scale in the photograph.

(c)

(a)

and lenses being used, the fi lm type and speed (if applicable) being used, and the photographer’s name and title. The log should also contain a table where each photograph will be logged. Each pho- tograph’s log should show the date and time the photograph was taken, the location of the picture, the f-stop and shutter speed settings, the lighting used and the lighting angle (if applicable), the angle of the camera, and a description of the subject of the picture. Some digital cameras produce an elec- tronic photography log. This log must be submitted along with notes and the written photography log form, as well as the testimony of the investigator, for the digital photographs to be considered for admissibility.

CRIME SCENE IMAGES

OVERVIEW PHOTOGRAPHS The fi rst pictures the photographer takes are overview photographs of the entire scene and surrounding area, includ- ing points of exit and entry. These photographs should be taken from the outside borders of the scene and must be taken from various angles. If the crime took place indoors, the entire room should be photographed to show each wall area. Rooms adjacent to the actual crime site must be similarly photographed. If the crime scene includes a body, photographs must show the body’s position and location relative to the entire scene. When taking overview photographs, the crime-scene photogra- pher should include at least one object in multiple overview photographs to help visually piece the scene together. This object is called a visual tag . Although one generally should avoid having indi- viduals present in photographs, it may be helpful to photograph witnesses in the locations from which they viewed the crime. This can help the jury deter- mine what a witness could or could not have seen from these locations. One may also wish to photo- graph the sight lines of suspects and victims. If a camera boom is available, the photographer should take pictures from overhead.

MEDIUM-RANGE PHOTOGRAPHS The next set of pictures should be medium-range photographs that show the layout of smaller signifi cant areas of the crime scene. Medium-range shots should be taken with evidence markers in place to show the spatial relationships between and among pieces of evidence in greater detail than in the overview photographs. A key medium-range photograph standard to all crime scenes is one that includes the “center” of the scene. In violent crimes, this usually includes the site where the victim was found and the surrounding area.

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RECORDING THE CRIME SCENE

CLOSE-UP PHOTOGRAPHS Close-up photographs, taken last, show the great- est detail of individual objects or evidence. The pictures must be taken at a 90-degree angle to the object, with and without evidence markers and scales. Scales should be placed as close to the evidence as possible without affecting it in any way. After the 90-degree photographs have been taken, photographs from other angles may be taken. For three-dimensional objects, oblique light- ing may be needed. It is also important to bracket close-up photographs. This means that the same photograph should be taken at varying f-stops and shut- ter speeds to ensure the best detail possible. Filters may also be important for close-up photographs. The most important close-up photographs are those depicting injuries and weapons lying near a body. After the body is removed from the scene, the surface beneath the body should be photographed.

At a minimum, there are four photographs required at a crime scene: an overview photograph, a medium-range photograph, a close-up photograph, and a close-up photograph with a scale. These photographs create an ade- quate visual record of the position and appearance of an item of evidence at a crime scene.

PHOTOGRAPHS AT NIGHT Photography at night can be very challenging. It is best to wait until morning, but there are a few methods to use if this is not possible. Firefi ghters or police offi cers commonly bring fl oodlights to outdoor crime scenes at night. Photographers often use refl ectors to focus fl ash il- lumination on both indoor and outdoor scenes. A technique called “painting with light” allows photographers to illuminate long distances at night. This involves mounting a camera on a tripod and locking the shutter open in com- plete darkness. The photographer then proceeds around the crime scene, fi r- ing off a fl ash to illuminate all areas of the crime scene—usually about three to four fl ashes in total. The shutter is then closed to capture the image. In place of painting with light, one may use multiple fl ash units that are placed strategi- cally around the crime scene. The units are synchronized to fl ash simultane- ously when the shutter is released.

All photographs of the crime scene should be repeated during daylight hours. Although many items of evidence may have been removed in the in- terim, it is advantageous to have overall views of the area in daylight.

INDOOR SCENES Typically, the earliest photographs of an indoor crime scene are overview photographs of the exterior of the building that locate the scene and any evidence present on the exterior. The next photographs are of the  entrance itself, then photographs are taken of the scene as viewed from the entrance. The photographer then moves around the interior of the scene in a clockwise or counterclockwise direction, taking photographs from each corner and possibly the middle of each wall to provide a complete 360-degree view of the scene. Medium-range photographs must then be taken of each wall, the fl oor, and the ceiling, as well as of the relative locations of groups of evidence from different angles. The crime-scene photographer should be con- scious of other rooms that may contain evidence and photograph them thor- oughly as well. Close-up photographs should be taken of all located evidence (with and without scales) and of injuries on a victim. Investigators should give special attention to locating and photographing any impressions made by footwear going into or out of an indoor scene.

OUTDOOR SCENES At outdoor crime scenes, especially those involving vehicles, the earliest photographs may be of the street signs closest to the scene. Overview photographs are then taken from the defi ned borders of the scene. Investigators note the positions from which these pictures were taken on the photography log using Global Positioning System (GPS) coordinates or by measuring the distance to the positions from the nearest roadways.

63

RECORDING THE CRIME SCENE

Medium-range photographs are taken of groups of evidence or of zones of a scene that is too large to photograph as a whole. Close-up photographs must be taken correctly because evidence at an outdoor scene rarely remains undisturbed for very long. If a vehicle is included in the scene or is the scene, overview photographs should be taken of the front and left side and then the back and right side. Particular attention should be paid to capturing license plates and vehicle identifi cation numbers (VINs) in the series of photographs taken. If the vehicle was stolen or burglarized, pictures should show where on the vehicle the culprit gained access. Aerial photography may be required for large outdoor scenes or to show the relationship of multiple scenes. It may also be useful to show weather conditions and traffi c patterns near an outdoor site.

ACCIDENT PHOTOGRAPHY The site of the accident is not simply the place where the wrecked cars are resting. The scene also includes the approach. As with other crime scenes, the objective in investigating an accident scene is to determine the how and why the events took place. This could lead an inves- tigator to retrace the path of the vehicle several blocks from the crash site. It is important to note any local traffi c control devices such as speed-limit signs and traffi c lights. Anything that should control a driver’s and/or pedestrian’s behavior must be documented.

The accident-scene photographer must get shots at various points along the approach to the impact site. This makes it possible for a reconstruction- ist to determine what a driver might have seen and when. It is important to establish possible obstructions a driver might have encountered. Another im- portant task for the photographer is to verify witnesses’ viewpoints. It must be confi rmed that what the witnesses say they saw could actually have been seen from their positions at the time of the accident.

One of the most helpful pieces of evidence for determining how the acci- dent occurred is the tire tracks. The photographer is not responsible for read- ing these marks, but he or she is expected to document them so that someone can. Several views should be taken of each mark to better determine direction- ality and length. Other marks may be present at the scene, such as marks on guardrails, poles, trees, buildings, and other vehicles.

The entire vehicle, not only the damaged portions, should be photographed (see Figure 5 ). This information can be useful in court if the driver claims he or she was struck by another car that caused the accident. If this alibi is accurate, there will be evidence of it in the photographs. Photographs should also be taken of the license plate, pedals, airbags, seat belts, speedometer, and lamp fi laments. Sometimes it is possible to verify which pedal the driver was press-

ing at the time of the accident. This may be possible if the driver’s shoes or bare feet took on the impression of the pedal, or if the pedal took on the impression of the sole of the shoe. An impression can also confi rm the identity of the driver when there is more than one occupant and no one admits to having been in the driver’s seat.

ARSON PHOTOGRAPHY Overview photographs of an arson scene should show the relative location of the scene, with the aid of street signs if possible. The arson scene also requires specifi c medium-range and close-up photographs of the likely point of entry, point of origin, and any areas of fi re activity. Close- up photographs are also required for all located evi-

dence. Photographers may use special lighting techniques or fi lters to show the maximum contrast between dark-colored arson debris and dark-colored

FIGURE 5 Photograph of the scene of an automobile accident.

64

RECORDING THE CRIME SCENE

backgrounds. Because perpetrators of arson crimes frequently return to the scene, it may be especially important to photograph the crowd outside an arson scene.

SEXUAL ASSAULT VICTIM PHOTOGRAPHY In cases involving sexual assault, overview photographs also should be taken of the scene and surrounding area. Medium-range photographs of the position of the victim in relation to the scene may be important. Medium-range and close-up photographs should be taken of any wounds the victim may have sustained. These may include cuts, bruises, or blunt-force-trauma wounds. However, given the nature of the crime and probable locations of wounds on the victim’s body, it is important that photographing be respectful. It is also important to photograph the cloth- ing the victim was wearing during the attack.

IMPRESSION PHOTOGRAPHY If tire or footwear impressions are found at a crime scene, overview and medium-range photographs should be taken to show the relative position and direction of the impressions. Close-up photo- graphs of tire and footwear impressions must be taken before the impression is cast. A tripod must be used to ensure the fi lm is arranged 90 degrees to the plane of view (see Figure 6 ). Lighting from the side of the impression (oblique lighting) should be utilized to provide the best detail and maximum contrast through shadowing. It is helpful to use a fl ashlight to determine the best angle light to photograph the impression. A scale must be included in the photo- graph so that a 1:1 ratio print can later be created for comparison to exemplar

FIGURE 6 A tripod and scale are used to take a close-up photograph of a tire impression marked with an evidence marker at 90 degrees. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

65

RECORDING THE CRIME SCENE

tires or footwear (see Figure 7 ). It may also be wise to include an identifying tag in the photograph to indicate where the impression was found and which part of the impression is represented in the photograph. A tire impression must be photographed using an overlapping photograph sequence, and a min- imum of eight feet of the tire impression should be photographed.

BLOODSTAIN PHOTOGRAPHY Overview and medium-range photographs should show the orientation and location of bloodstain evidence. Overview photographs are taken of the entire crime scene, including overviews of the bloodstain patterns within the scene. If multiple bloodstain patterns cover a large surface area, the area can be subdivided into zones or a grid. Close-up photographs, with a scale in place, should be taken of each pertinent stain or group of stains. If analysis of a blood spatter pattern is done at the scene, photographs should be taken of the drawn area of convergence and area of origin. Bloodstains detected with luminol must be photographed in complete darkness. The camera’s shutter is locked open for approximately three min- utes at an f-stop of 22, and a fl ash at 1/16 power is fi red at the beginning of the three minutes.

LATENT FINGERPRINT PHOTOGRAPHY Close-up photographs of latent (hid- den) fi ngerprints must show the ridge details of the fi ngerprints for possible identifi cation of their source. Any developed fi ngerprints should be photo- graphed before they are retrieved. Photographs can be taken by a special latent fi ngerprint camera that is designed to create a 1:1 photograph of fi n- gerprint evidence (see Figure 8 ) or by a standard fi lm or digital camera fi t- ted with an adapter. Commonly, black-and-white fi lm photography is used to show greater contrast. An item label should be included in the photograph in order to identify the location of the fi ngerprint. The picture must be taken at 90 degrees using a high f-stop and oblique lighting for maximum detail. A fi ngerprint should be photographed using SLR color print fi lm or a stan- dard digital camera, and a scale should be included in the photograph. If the

FIGURE 7 This photograph of a tire impression includes a scale so that a 1:1 image can later be produced. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

66

RECORDING THE CRIME SCENE

pattern is enhanced with a blood reagent, photographs should be taken as the pattern develops.

SHOOTING INCIDENT PHOTOGRAPHY As with any other type of crime scene, the fi rst step in photographing shooting incidents is capturing the overall set- ting. Before any specifi c attention can be paid to bullets or cartridge cases, a complete 360-degree view of the site should be photographed. In addition to pictures of the scene itself, photographs must also be taken from the view- points that involved parties or witnesses might have had. One of the most diffi cult parts of photographing a shooting scene is fi nding the bullet. Bul- lets have the ability to ricochet, infi ltrate, and embed themselves into various surfaces. They also might fragment on impact, or their shape may become distorted. The damage done by a fi red bullet must be photographed as well as the bullet itself.

USE OF DIGITAL PHOTOGRAPHY

Digital photography of crime scenes has many advantages. Investigators can observe the images immediately after taking them to ensure that important photographs are clear and show the best possible detail. Also, the resolution available on many modern digital cameras can exceed six megapixels, whereas the maximum resolution offered by an SLR camera is equivalent to about fi ve megapixels. As technology advances, digital photography provides other ad- vantages over traditional fi lm. For example, photographers can electronically stitch together individual images of a crime scene that were captured with a digital camera to create a nearly three-dimensional panoramic view of the crime scene (see Figure 9 ). With the aid of a computer, any area of the scene captured digitally can be enhanced and examined in fi ne detail.

The very nature of digital images, however, opens digital photography up to important criticisms within forensic science casework. Because the photo- graphs are digital, they can be easily manipulated by using computer software. This manipulation goes beyond traditional photograph enhancement such as

FIGURE 8 A specialized camera is used to photograph latent fi ngerprints on a cereal box (a) and creates a 1:1 photograph (b). Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

(a)

(b)

WebExtra 1

Making a Photographic Record of the Crime Scene www.my crimekit.com

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RECORDING THE CRIME SCENE

adjusting brightness and contrast or color balancing. Computer software al- lows a person to crop a photo, remove repeating patterns such as window screens, superimpose images, and alter photos signifi cantly in many other ways. Because the primary function of crime-scene photography is to provide an accurate depiction, this is a major concern.

The crime-scene photographer using digital photography also has to be conscious of the kind of fi le format in which the crime-scene images are saved. Digital images are preserved by either lossy or lossless compression. Lossy compression condenses fi les by discarding some image information. The in- formation lost during this compression is irretrievable. An example of this type of fi le is the JPEG (Joint Photographic Experts Group) format. This for- mat is usually available in low-cost consumer digital cameras. A JPEG may be suitable for general crime-scene overview photographs; however, any pho- tograph to be used for in-depth evaluation of an object or subject, such as a comparison analysis or analysis of body wounds, requires images without compression loss. Lossless compression condenses fi les without discarding information so no important image information is lost. A tagged image fi le format (TIFF) or a raw image (RAW) format satisfi es this requirement. RAW stores the highest quality image but requires special software for viewing. High-end digital cameras generally offer the option of capturing an image in a number of formats.

To ensure that their digital images are admissible, many jurisdictions have developed or are developing standard operating procedures (SOPs) for the use of digital photography. Sometimes admissibility requirements dic- tate that a detailed and accurate photography log be kept by the crime-scene photographer to be submitted along with the testimony of the photographer

FIGURE 9 Individual images (top) are shown before being electronically stitched together into a single panoramic image (bottom). Individual photographs should be taken with an about 30-percent overlap. Courtesy Imaging Forensics, Fountain Valley, CA, www.imagingforensics.com

lossless compression A compression method for digital fi les that decreases the fi le size without discarding digital data.

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RECORDING THE CRIME SCENE

as to the accuracy of the photographs. The goal is to set guidelines for determining the circumstances under which digital photogra- phy may be used and to establish and enforce strict protocols for image security and chain of custody. For example, digital photo- graphs should be copied only to writable disks. They should never be placed on rewritable disks that can be altered or erased. If an image is to be enhanced in some way, the new image must be saved separately, not written over the original image.

The digital era promises new and elegant approaches to docu- menting the crime scene. Cameras such as that shown in Figure 10 are capable of taking dozens of digital images while scanning the crime scene. Photographic and laser data from multiple scan loca- tions are combined to produce 3-D models of the scene in full color that can be viewed from any vantage point, measured, and used for analysis and courtroom presentations.

VIDEO DOCUMENTATION

The use of digital videorecording at crime scenes is becoming in- creasingly popular because the cost of this equipment is decreasing. Videorecording of crime scenes is even required in some jurisdictions as a preliminary “tour” of the scene.

The same principles used in crime-scene photographs apply to videorecording. As with conventional photography, videorecording should include the entire scene and the immediately surrounding area. Long shots as well as close-ups should be taken in a slow and systematic manner. The way the investigator moves through the scene should be logical and should illustrate potential paths of entry, exit, and movement. Furthermore, it is de- sirable to have one crime-scene investigator narrate the events and scenes being taped while another does the actual shooting. Only the narrator’s voice should be heard, and no personnel should be in the shots.

Videorecording can have advantages over still photography in certain sit- uations. For example, modern video cameras allow the user to play back the tape of a scene and check it for completeness. Video can be especially help- ful in arson scenes, where still photographs have trouble showing detail, and where determining the path of the fi re is very important. In addition, many video cameras can also take still photographs, and on a computer stills can be created from the tape. Video essentially combines notes and photography. Some cameras even have a “night vision” feature, which is similar to infrared photography.

However, there are some disadvantages to videorecording crime scenes. First, although some cameras have a stabilization feature, most cameras will inevitably shake during fi lming. Also, zooming and panning can be very sloppy; these techniques should be used only occasionally and should be done very slowly. Extra noise due to wind or other investigators talking can obscure narration or may be inappropriate and damaging. Because of the “on the spot” nature of the narration, investigators may stumble over words, which can be confusing when a video is used in court. To avoid this, some investigators re- cord the video with the sound off and dub notes over it later.

Although videorecording can capture the sounds and scenes of the crime site with relative ease, the technique cannot be used in place of still photogra- phy at this time. The still photograph remains unsurpassed in defi ning details for the human eye.

FIGURE 10 A computer- controlled scanner has both a high-resolution, professional digital camera and a long-range laser rangefi nder. The tripod- mounted device rotates a full 360 degrees, taking dozens of photographs and measuring millions of individual points. Photographic and laser data from multiple scan locations are  combined to produce 3-D models of the scene. Courtesy 3D Tech, Inc., Durham, NC 27713, www.deltasphere.com

WebExtra 2

Creating a 3-D model of a crime scene with the ability to measure relevant areas of the scene. www.mycrimekit.com

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RECORDING THE CRIME SCENE

Quick Review • Digital photography is used widely for documenting crime scenes. • The crime scene should be recorded in a minimum of four photographs:

an overview photograph, a medium-range photograph, a close-up photo- graph, and a close-up photograph with a scale.

• Special techniques and unique considerations apply when photograph- ing indoor scenes, outdoor scenes, night scenes, accident scenes, arson scenes, sexual assault victims, impression evidence, bloodstain evidence, latent fi ngerprint evidence, and shooting incidents.

• Digital images are preserved by either lossy or lossless compression. • Although many digital cameras have far surpassed the common fi lm cam-

era in resolution and ease of use, admissibility issues may still exist in the use of digital images during legal proceedings.

• Video documentation is helpful for showing possible paths and for com- bining note narration with photography. However, still pictures are still required for their ability to show detail and especially for close-up views of evidence.

Sketching the Crime Scene Once the crime-scene investigator has taken suffi cient notes and photographs, he or she sketches the scene. The sketch serves many important functions in the legal investigation of a crime. If done correctly, a sketch can clearly show the layout of an indoor or outdoor crime scene and the relationship in space of all the items and features signifi cant to the investigation. Sketches are es- pecially important to illustrate the location of collected evidence. A sketch can clarify objects and features already described in notes or shown in photo- graphs. Sketches can also show measurements over long distances and the topography of outdoor scenes. Possible paths of entry, exit, and movement through the scene may be speculated from a good sketch. Additionally, the state of the scene illustrated by the sketch may help to demonstrate the feasi- bility of a witness’s testimony. To be effective, a sketch must be clear enough to be used in reconstruction by other investigative personnel and to illustrate aspects of the crime scene to a jury.

THE ROUGH SKETCH

The investigator may have neither the skill nor the time to make a polished sketch of the scene. However, this is not required during the early phase of the investigation. What is necessary is a rough sketch containing an accurate depiction of the dimensions of the scene and showing the location of all objects having a bearing on the case. It shows all recovered items of physical evidence, as well as other important features of the crime scene (see Figure 11 ).

The following tools are required to create the sketch (see Figure 12 ):

• Graph paper or drawing paper • Two measuring tapes • Clipboard or drawing surface • Pencils • Straightedge ruler

rough sketch The rudimentary fi rst sketch created at the crime scene with care for accuracy in depicting dimensions and locations but no concern for aesthetic appearance.

70

RECORDING THE CRIME SCENE

FIGURE 11 A rough sketch of a crime scene. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

• Erasers • Compass or GPS device • Optional tools including drawing compasses, protractors (half- or full-

circle), architect scales, French curves, drafting triangles, and rolling mea- suring devices

71

RECORDING THE CRIME SCENE

All sketches must include the following features:

• The title block contains the case number, the agency number (if applica- ble), the name and title of the artist, the location of the scene, and the date and time at which the sketch was created. It may also state the victim’s name, the names of any suspects, or the type of crime. The title block should appear in the lower right corner of the sketch paper.

• The legend should contain the key to the identity and dimensions of objects or evidence and may be represented by symbols, letters, or numbers.

• The compass should show an arrow to denote north in relation to the scene.

• The body of the sketch contains the drawing itself and all dimensions and objects located within it.

CREATING THE SKETCH

1. Defi ne the boundaries of the sketch. These may be walls for an indoor sketch. Make sure that the area within these boundaries includes all the pertinent objects and evidence.

2. Establish known points from which to measure the locations of objects and evidence. These points should be fi xed. These can be walls or doors in indoor scenes. Trees, telephone poles, street signs, or natural features (e.g., boulders) can be used for outdoor scenes.

3. The walls or boundaries should be drawn in fi rst, leaving as much room as possible for the contents. If walls are used, their dimensions should be recorded.

FIGURE 12 A basic kit for sketching the crime scene. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

72

RECORDING THE CRIME SCENE

4. Measurements should be taken from the fi xed points to pieces of evidence fi rst. There are three methods of measurement from the two points of reference.

• The rectangular method measures two distances to an object that make a right angle with each other and to two fi xed, fl at surfaces. These sur- faces are usually walls (see Figure 13[a] ).

• The triangulation method measures the distance of the object from two fi xed points of known distance from each other. This forms a triangle. In an indoor scene these points are usually the corners of a room (see Figure 13[b] ).

• The baseline method is especially useful for outdoor scenes. First, two fi xed objects on opposite sides of the scene are located (designated A and B). A line is then made between them and measured. Each object or piece of evidence has a line drawn from it to the baseline to make a 90-degree angle with the baseline. The distance of the line from the ob- ject to the baseline is then measured, along with its point of intersection with the baseline (see Figure 13[c] ).

• The polar coordinates method uses only one reference point. The sketch in Figure 13(d) shows the distance and angle at which an object is located in the scene relative to the reference point.

N

7.75 feet

15 ft

(a) Rectangular Method

A

600

B (d) Polar Coordinates Measurement

16.5 feet 17.25 ft

BA

(b)Triangulation Measurement

10.75 ft 6 7 8 9 10 11 12

6.5 feet

N A

B

N

N

(c) Baseline Method

18 .5

fe et

FIGURE 13 (a) The rectangular measurement method; (b) the triangulation measurement method; (c) the baseline measurement method; and (d) the polar coordinates measurement method.

73

RECORDING THE CRIME SCENE

Distances shown on the sketch must be accurate and not the result of a guess or estimate. For this reason, all measurements should be made with a tape measure and confi rmed by two people. The simplest way to label the location of an item in a sketch is to assign it a number or letter. A legend will then correlate the number or letter to the item’s description and di- mensions. Symbols for objects should be consistent. Typically, items of evi- dence are assigned numbers (possibly correlating to their evidence marker number), and nonevidentiary objects are assigned letters. The distances and dimensions of these objects not considered to be evidence are measured, recorded, and drawn last. Distances between objects also can be measured and drawn. It is very important that units of measure are kept the same throughout the sketch. Usually inches and feet are used in the United States because those measurements are easily understood by the investigative per- sonnel and the jury.

THE FINISHED SKETCH

Unlike the rough sketch, the fi nished sketch is constructed with care and concern for aesthetic appearance. The fi nished sketch must be drawn to scale. The legend should contain the scale (e.g., 1/2" � 1'). When the fi nished sketch is completed, it must refl ect information contained within the rough sketch to be admissible evidence in a courtroom. An indoor overview sketch shows the fl oors of one or more rooms, doors and windows, and any evidence or objects on the fl oor (see Figures 14 and 15 ). An outdoor overview sketch is like an aerial view of a small or large outdoor scene. A fi nal sketch can be done by an investigator or a hired professional. It can be done by hand in pen or by computer (see Figure 16 ).

The process of computer-aided drafting (CAD) has become the standard method for reconstructing crime scenes from rough sketches (see Figure 17 ). The software, ranging from simple, low-cost programs to complex, expensive ones, contains predrawn objects, such as intersections, roadways, buildings, and rooms, onto which information can be added. A generous symbol library provides a variety of images that can be used to add intricate details, such as blood spatters, to a crime-scene sketch. Equipped with a zoom function, com- puterized sketching programs can enlarge a specifi c area for a more detailed pic- ture. These sketches may also be able to show bullet trajectories in scenes where a gun was involved. CAD programs allow users to select a scale size so that the fi nal product can be produced in a size suitable for courtroom presentation.

Three-dimensional CAD sketches can also be created. These sketches show the nature of the crime scene from many angles. This can be helpful in crime reconstruction and in the trial setting. Some can also be animated to show how the events suggested in the reconstruction would lead to the fi nal state of the scene.

Quick Review • The crime scene sketch plays an important role in the legal investigation of

a crime by clearly showing possible points of entry and/or exit, evidence locations, and the general layout of the crime scene. It will also refresh the investigator’s memories about the case after time has passed.

• The rough sketch is made at the scene to show basic measurements of the scene and spatial relationships between items.

• The fi nished sketch is created from the rough sketch with care and con- cern for appearance. It must include a scale, and it may be created using a computer-aided drafting program.

fi nished sketch The perfected fi nal sketch that is constructed with care and concern for aesthetic appearance and drawn to scale.

computer-aided drafting (CAD) The process of creating a scaled drawing using specially designed computer software.

74

RECORDING THE CRIME SCENE

N

‘D - 3' 4¾" FROM FLOOR

SCALE: ¼" = 1 FOOT

CASE 10-789-90 301 N. CENTRE ST. March 15, 2007 11: 40 PM HOMICIDE

VICTIM: LESTER W. BROWN INVESTIGATOR: SGT. L.A. DUFFY ASS’T BY: PTLM. R.W. HICKS

LEGEND: A. COCKTAIL GLASS B. TELEPHONE C. VICTIM D. BULLET HOLE E. BLOOD STAINS F. SHELL CASING CAMERA LOCATIONS

FIGURE 14 An overview fi nished sketch of a room interior. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

75

RECORDING THE CRIME SCENE

FIGURE 15 An overview fi nished sketch of an offi ce scene. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

76

RECORDING THE CRIME SCENE

FIGURE 16 A fi nished sketch of an outdoor crime scene. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

77

RECORDING THE CRIME SCENE

FIGURE 17 Construction of a crime-scene diagram with the aid of a computer-aided drafting program. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

CHAPTER REVIEW

• Because investigators have only a limited amount of time to work a crime site in its untouched state, the opportunity must not be lost.

• Crime-scene notes should include contact information, per- sonnel information and movements, task assignments, ob- servations of the victim and scene, and information about the evidence before and after it is processed.

• Recording notes on digital voice recorders is advantageous, but investigators should take care to speak clearly and avoid including side conversations.

• Film is made of a sheet of light-reactive silver halide grains. The light-capturing ability of the grains is called fi lm speed, and higher-speed fi lms have bigger grains in order to cap- ture light faster. This means that higher-speed fi lms create grainier photographs.

• Digital cameras feature a light-sensitive microchip that cap- tures light on each of millions of tiny picture elements, called pixels. The light is recorded on each pixel as a specifi c charge that will later be electronically translated to an image. The number of pixels on a camera is measured in the millions, called megapixels, and directly affects an image’s resolution.

• SLR and DSLR cameras allow for the use of a wide range of lenses including normal lenses, telephoto lenses, wide-angle lenses, macro lenses, and multipurpose lenses. The kind of lens used affects the appearance of the image.

• The aperture and shutter speed regulate the amount of light gathered by the camera. These settings can be manually ad- justed on SLR and DSLR cameras.

• The f-stop determines depth of fi eld, or the amount of area in the foreground and background that is in focus. The higher the f-stop, the smaller the aperture and the greater the depth of fi eld. Landscape and portrait settings on a digital camera adjust for higher and lower f-stops, respectively.

• The color temperature of the light source used will make a photographic image appear orangish or bluish. Many digital cameras combat this with “white balance” capability. Ex- posure compensation and electronic fl ashes can be used to capture images of dark or light subjects. Flash units, or slave fl ashes, are helpful to provide oblique or versatile illumination.

• Filters are used with SLR or DSLR cameras to block certain wavelengths of light (barrier fi lters) or allow in only certain wavelengths of light (bypass fi lters). Filters can be used to show greater detail in photographs by adjusting the appear- ance of specifi c colors.

• Tripods can greatly improve photograph quality by prevent- ing blurriness caused by the movement of the photographer’s hand. They also help ensure 90-degree close-up photographs of evidence

• Digital photography is used widely for documenting crime scenes.

78

RECORDING THE CRIME SCENE

• The crime scene should be recorded with a minimum of four photographs: an overview photograph, a medium-range photograph, a close-up photograph, and a close-up photo- graph with a scale.

• Special techniques and unique considerations apply when photographing indoor scenes, outdoor scenes, night scenes, accident scenes, arson scenes, sexual assault victims, impres- sion evidence, bloodstain evidence, latent fi ngerprint evi- dence, and shooting incidents.

• Digital images are preserved by either lossy or lossless com- pression.

• Although many digital cameras have far surpassed the com- mon fi lm camera in resolution and ease of use, admissibility issues may still exist in the use of digital images during legal proceedings.

• Video documentation is helpful for showing possible paths and for combining note narration with photography. How- ever, still pictures are still required for their ability to show detail and especially for close-up views of evidence.

• The crime scene sketch plays an important role in the legal investigation of a crime by clearly showing possible points of entry and/or exit, evidence locations, and the general lay- out of the crime scene. It will also refresh the investigator’s memories about the case after time has passed.

• The rough sketch is made at the scene to show basic mea- surements of the scene and spatial relationships between items.

• The fi nished sketch is created from the rough sketch with care and concern for appearance. It must include a scale, and it may be created using a computer-aided drafting program.

KEY TERMS

aperture

color temperature

computer-aided drafting (CAD)

depth of fi eld

digital photography

REVIEW QUESTIONS

1. Three methods for recording the crime scene are _____________ , _____________ , and _____________ .

2. True or False: The note-taking process begins with the call to a crime-scene investigator to report to a scene. ______________

3. The crime-scene notes should include a precise record of per- sonnel movements in and out of the scene, starting with the ______________ .

4. True or False: Crime-scene notes should be written from memory back at the laboratory. ______________

5. Before evidence is collected, it must be fully described in the investigator’s ______________ .

6. True or False: When an injured or deceased victim is pres- ent at the scene, the state of the body before being moved should be observed but not recorded. ______________

7. True or False: The value of crime-scene photographs lies in their ability to show the layout of the scene, the position of witnesses, and the physical relationship of people to one an- other in the scene. ______________

8. The most commonly used camera for crime-scene photogra- phy is the ______________ camera, which can be fi lm or digital.

9. True or False: The lens of the camera is the mechanism for bending light to focus the image on the fi lm or digital micro- chip, and the kind of lens is determined by the lens’s focal length. ______________

10. The camera ______________ is the measure of the diam- eter of the opening of the diaphragm, and it is adjusted on a fi lm or digital camera by adjusting the f-stop.

11. The ______________ , measured in fractions of a second, is the length of time the fi lm or microchip is exposed to light.

12. The ______________ of a photograph is the amount of area in the foreground and background of an in-focus object that is also relatively in focus.

13. True or False: On the color temperature scale, a “hot” light source has a red-orange hue, whereas a “cold” light source has a blue hue. ______________

14. The ______________ is the most commonly used type of fl ash in photography. This type of fl ash is usually on the top or front of a camera.

15. True or False: Film may be either color print fi lm (produc- ing a negative to be developed), color slide fi lm (producing transparent positives on slides for presentations), black-and- white fi lm, or infrared fi lm. ______________

fi lm speed

fi nished sketch

f-stop

lossless compression

megapixel

photography log

rough sketch

shutter speed

single lens refl ex (SLR) or DSLR camera

79

APPLICATION AND CRITICAL THINKING

1. What type of lens would a photographer probably use to create each of the following photos?

a) An extreme close-up photo of a fi ber found at a crime scene

b) A medium-range shot of part of a wall

c) A photo showing the entire length of a wall

2. What kind of fi lter would a photographer probably use for the following shots?

a) A photo of a fi ngerprint imaged with a fl uorescent powder

b) A photo in which the investigator wishes to highlight an area of a particular color

c) A piece of evidence that is diffi cult to see against a spe- cifi c background color

3. The digital camera offers a wide range of options for optimiz- ing the photograph of a subject. What setting would be used in each of the following situations?

a) Capturing subjects in motion

b) Reducing exposure time

c) Increasing depth of fi eld

d) Shooting in a particular type of light, such as fl uorescent lighting

e) Calculating the best setting for light conditions at the center of a fi eld

16. High-speed fi lms produce grainier photographs because of the (large, small) size of the fi lm grains.

17. A digital camera captures light on a light-sensitive ______________ .

18. True or False: Crime-scene photographers generally use sim- ple “point and shoot” digital cameras. ______________

19. A(n) ______________ fi lter blocks one wavelength of light bouncing off the subject and allows all others to reach the fi lm or microchip.

20. The ______________ , fi lled out by the crime-scene photog- rapher, should include the case and scene information and the parameters of each photograph.

21. The most important prerequisite for photographing a crime scene is to have it in a(n) ______________ condition.

22. True or False: Each crime scene should be photographed as completely as possible in a logical sequence that includes the area in which the crime actually took place and all adjacent areas where important acts occurred. ______________

23. The succession of photographs taken at a crime scene is ______________ photographs fi rst, ______________ pho- tographs second, and ______________ photographs last.

24. True or False: Overview photographs should include only points of entry and points of exit. ______________

25. To show the greatest detail of individual objects or evi- dence, close-up photographs must be taken at an angle of ______________ and with and without evidence markers and scales.

26. A technique called ______________ may be used to illumi- nate long distances in total darkness in night photography.

27. True or False: In indoor or outdoor scenes the crime-scene photographer moves around the boundary of the scene in a clockwise or counterclockwise direction, taking photographs from many vantage points and angles to provide a complete 360-degree view of the scene. ______________

28. In ______________ cases it may be especially important to photograph the crowd outside the scene because perpetra- tors of these crimes frequently return to the scene.

29. True or False: Victims of violent crimes may have wounds that should be photographed, but this should be done respect- fully. ______________

30. True or False: Close-up photographs of tire and footwear im- pressions at a crime scene must be taken after the impres- sion is cast. ______________

31. True or False: The traditional fi lm cameras available on the market produce photographs with greater resolution than digital cameras do. ______________

32. To ensure that their digital images will be admissible, many jurisdictions have developed or are developing ______________ for the use of digital photography to avoid the possibility of enhancement or doctoring of crime- scene photographs.

33. The process of ______________ the crime scene essentially combines note taking and photography.

34. An investigator need only draw a(n) ______________ sketch at the crime scene to show its dimensions and perti- nent objects.

35. When creating a rough sketch, measurements should be taken from fi xed points to pieces of evidence by using either the ______________ , ______________ , ______________ , or ______________ method.

36. True or False: The distances and dimensions shown on the sketch can be a guess or estimate, and the use of a tape measure is not required. ______________

37. Unlike the rough sketch, the ______________ is con- structed with care and concern for aesthetic appearance and must be drawn to scale.

38. ______________ programs provide an extensive symbol library and may create a three-dimensional sketch.

RECORDING THE CRIME SCENE

80

RECORDING THE CRIME SCENE

4. What important elements are missing from the following crime-scene sketch?

81

82

Collection of Crime-Scene

Evidence

From Chapter 4 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

MURDER AND THE HORSE CHESTNUT TREE Roger Severs was the son of a wealthy English couple, Eileen and Derek Severs, who were reported missing in 1983. Police investigators were greeted at the Severs home by Roger, who at fi rst explained that his parents had decided to spend some time in London. Suspicion

of foul play quickly arose when investigators located traces of blood in the residence. More blood was found in Derek’s car and there were signs of blood spatter on the garage door. Cu- riously, a number of green fi bers were located throughout the house, as well as in the trunk of Derek’s car.

A thorough geological examination of soil and vegetation caked onto Severs’s car wheel rims seemed to indicate that the car had been in a location at the edge of a wooded area. Closer examination of the debris also revealed the pres- ence of horse chestnut pollen. Horse chestnut is an exceptionally rare tree in the region of the Severs residence.

Using land maps, a geologist located possible areas where horse chestnut pollen might be found. In one of the locations, inves- tigators found a shallow grave that contained the bludgeoned bodies of the elder Severses. Not surprisingly, they were wrapped in a green

blanket. A jury rejected Roger’s defense of diminished ca- pacity and found him guilty of murder.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Defi ne physical evidence. • Review the common types of physical evidence

encountered at crime scenes. • Describe proper techniques for handling evidence to

avoid damage or contamination. • Understand collecting and packaging procedures for

common types of physical evidence. • Defi ne and understand the concept of chain of custody. • List the steps that are typically required to maintain

appropriate health and safety standards at the crime scene.

• Discuss the implications of the Mincey and Tyler cases.

Collection of Crime-Scene

Evidence F. Lukasseck/Jupiter Images F. Lukasseck/Jupitp er Imagesg

84

COLLECTION OF CRIME-SCENE EVIDENCE

A s automobiles run on gasoline, crime laboratories “run” on physical evidence . Physical evidence includes any and all objects that can estab- lish that a crime has or has not been committed or that can provide a link

between a crime and its victim or perpetrator. However, for physical evidence to aid the investigator, its presence must

fi rst be recognized at the crime scene. If investigators were to gather all the natural and commercial objects within a reasonable distance of the scene so that the scientist could uncover signifi cant clues from them, the deluge of material into the crime laboratory would quickly immobilize the facility. This is why it is important for investigators to be discriminating and to get it right the fi rst time. The collection of evidence must be thorough enough to include as many pertinent clues as possible but selective enough not to bog down the laboratory. Physical evidence achieves its value in criminal investigations only when the investigator collects it selectively and with a thorough knowledge of the crime laboratory’s techniques, capabilities, and limitations.

Common Types of Physical Evidence It would be impossible to list all the objects that could conceivably be important to a crime. Every crime scene has to be treated on an individual basis, having its own peculiar history, circumstances, and problems. However, it is practical to be aware of types of items whose scientifi c examination is likely to yield signifi cant results in ascertaining the nature and circumstances of a crime. The investigator who is thoroughly familiar with the recognition, collection, and analysis of these items, as well as with laboratory procedures and capabilities, can make logical decisions when faced with uncommon and unexpected circumstances at the crime scene. Equally important, a qualifi ed evidence collector cannot rely on collection procedures memorized from a pamphlet but must be able to make innovative, on-the-spot decisions at the crime scene.

Blood, Semen, and Saliva All suspected blood, semen, or saliva—liquid or dried, animal or human—presents in a form that suggests a relationship to the offense or people involved in a crime. This category includes blood or semen dried onto fabrics or other objects, as well as cigarette butts that may contain saliva residues. These substances are subjected to serological and biochemical analysis to determine identity and possible origin.

Documents Any handwriting and typewriting submitted so that authenticity or source can be determined. Related items include paper, ink, indented writings, obliterations, and burned or charred documents.

Drugs Any substance in violation of laws regulating the sale, manufacture, distribution, and use of drugs.

Explosives Any device containing an explosive charge, as well as all objects removed from the scene of an explosion that are suspected to contain the residues of an explosive.

Fibers Any natural or synthetic fi ber whose transfer may be useful in estab- lishing a relationship between objects and/or people.

Fingerprints All prints of this nature, hidden (latent) and visible. Firearms and Ammunition Any fi rearm, as well as discharged or intact

ammunition, suspected of being involved in a criminal offense. Glass Any glass particle or fragment that may have been transferred to a

person or object involved in a crime. This category includes windowpanes containing holes made by a bullet or other projectile.

Hair Any animal or human hair present that could link a person with a crime.

physical evidence Any object that can establish that a crime has or has not been committed or can link a crime and its victim or perpetrator.

85

COLLECTION OF CRIME-SCENE EVIDENCE

Impressions Tire markings, shoe prints, depressions in soft soils, and all other forms of tracks. Glove and other fabric impressions, as well as bite marks in skin or foodstuffs, are also included in this category.

Organs and Physiological Fluids Body organs and fl uids submitted for analysis to detect the possible existence of drugs and poisons. This category includes blood to be analyzed for the presence of alcohol and other drugs.

Paint Any paint, liquid or dried, that may have been transferred from the surface of one object to another during the commission of a crime. A  common example is the transfer of paint from one vehicle to another during an automobile collision.

Petroleum Products Any petroleum product removed from a suspect or recovered from a crime scene. The most common examples are gasoline residues removed from the scene of an arson and grease or oil stains whose presence may suggest in- volvement in a crime. Plastic Bags A disposable polyethylene bag such as a gar- bage bag that may be evidential in a homicide or drug case. Examinations are conducted to associate a bag with a similar bag in the possession of a suspect. Plastic, Rubber, and Other Polymers Remnants of these man- ufactured materials recovered at crime scenes may be linked to objects recovered in the possession of a criminal suspect. Powder Residues Any item suspected of containing pow- der residues resulting from the discharge of a fi rearm (see Figure 1 ). Serial Numbers This category includes all stolen property submitted to the laboratory for the restoration of erased iden- tifi cation numbers. Soil and Minerals All items containing soil or minerals that could link a person or object to a particular location. Common examples are soil imbedded in shoes and insulation found on garments. Tool Marks This category includes any object suspected of containing the impression of another object that served as a tool in a crime. For example, a screwdriver or crowbar could produce tool marks by being impressed into or scraped along a wall.

Vehicle Lights The examination of vehicle headlights and taillights is normally conducted to determine whether a light was on or off at the time of impact.

Wood and Other Vegetative Matter Any fragments of wood, sawdust, shavings, or vegetative matter discovered on clothing, shoes, or tools that could link a person or object to a crime location.

Quick Review • Biological crime-scene evidence includes blood, saliva, semen, DNA, hair,

organs, and physiological fl uids. • Impression crime-scene evidence includes tire markings, shoe prints,

depressions in soft soils, all other forms of tracks, glove and other fabric impressions, tool marks, and bite marks.

• Manufactured items considered common items of crime-scene evidence include fi rearms, ammunition, fi bers, paint, glass, petroleum products, plastic bags, rubber, polymers, and vehicle headlights.

FIGURE 1 The gun is fi red at a set distance from the target, and the gun-powder left on the target is compared to powder stains on a victim’s clothing. The density and shape of the powder stains vary with the distance the gun was fi red. Mikael Karlsson\ Arresting Images Royalty Free

86

COLLECTION OF CRIME-SCENE EVIDENCE

Evidence-Collection Tools The well-prepared evidence collector arrives at a crime scene with a large assortment of packaging materi- als and tools ready to encounter any type of situation. These tools are usually kept in an evidence-collection kit (see Figure  2 ).

• Notebook • Pen (black or blue ink) • Ruler • Chalk or crayons • Magnifying glass • Flashlight • Disposable forceps and similar tools, which may be

needed to pick up small items • Scalpels or razor blades • Swabs and medicine droppers for presumptive

testing • Gauze or sterile cloth • Unbreakable plastic pill bottles with pressure lids • Evidence sealing tape • Evidence tags (indoor) or fl ags (outdoor) (see

Figure 3 ) • Various size paper bags, boxes, and manila envelopes • Red “biohazard” labels • Paper for wrapping or for creating “druggist folds” • Alternate light source (see Figure 4 ) • Lifting tape for gathering hair or trace evidence

FIGURE 2 A typical evidence-collection kit. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

FIGURE 3 Evidence fl ags are used for outdoor crime scenes. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

87

COLLECTION OF CRIME-SCENE EVIDENCE

• Vacuum collector with fi lters • Fingerprint powders, brushes, and lifters • Disposable gloves, face masks, and shoe covers

MOBILE CRIME LABORATORIES

In recent years, many police departments have gone to the expense of purchasing and equipping mobile crime laboratories for their evidence technicians. However, the term mobile crime laboratory is a misnomer. These vehicles carry the necessary supplies to protect the crime scene; to photograph, collect, and package physical evidence; and to perform latent print development. They are not designed to carry out the functions of a chemical laboratory. Crime-scene search vehicle would be a more appropri- ate but perhaps less dramatic name for such a vehicle (see Figure 5 ).

Procedures for Collecting and Packaging Physical Evidence Physical evidence can be anything from massive objects to microscopic traces. Many items of evidence are obvious when present, but others may be detected only through examination in the crime laboratory. For example, minute traces of blood may be discovered on garments only after a thorough search in the laboratory, or the presence of hairs and fi bers may be revealed in vacuum

FIGURE 4 An example of an alternate light source in use. This can be used to visually enhance many types of evidence. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

88

COLLECTION OF CRIME-SCENE EVIDENCE

sweepings or on garments only after close laboratory scrutiny. For this reason, investigators should collect possible carriers of trace evidence in addition to more discernible items. This may include vacuum sweepings, fi ngernail scrap- ings, clothing, and vehicles.

The investigator should vacuum critical areas of the crime scene and submit the sweepings to the laboratory for analysis. The sweepings from dif- ferent areas must be collected and packaged separately. A portable vacuum cleaner equipped with a special fi lter attachment is suitable for this purpose (see Figure 6 ). Fingernail scrapings from individuals who were in contact with other individuals may contain minute fragments of evidence capable of pro- viding a link between assailant and victim. The investigator should scrape the undersurface of each nail with a dull object such as a toothpick to avoid cut- ting the skin. These scrapings will be subjected to microscopic examination in the laboratory. All clothing from the victim and suspect(s) should be collected and packaged separately. These objects will be further examined at the labora- tory for trace, fi ber, and hair evidence.

FIGURE 5 An inside view of a mobile crime-scene van: (a) driver’s side and (b) passenger’s side. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

P O L I C E GENERATOR

COMPARTMENT

P O L I C E

FIRST

AID

REFRI- GERATOR

FORENSIC KIT STORAGE

SINK

89

COLLECTION OF CRIME-SCENE EVIDENCE

When a vehicle is involved in a crime, investigators should pay particular attention to signs of a cross-transfer of evidence between the car and the victim—this includes blood, tissue, hair, fi bers, and fabric impressions. Traces of paint or broken glass may be located on the victim or roadway. The entire car should be processed for fi ngerprints. In cases in which the car was used for transportation, more attention may be given to the interior of the car. However, all areas of the vehicle, inside and outside, should be searched with equal care for physical evidence.

HANDLING EVIDENCE

Investigators must handle and process physical evidence in a way that prevents any changes in it between the time the evidence is removed from the crime scene and the time it is received by the crime laboratory. Changes can arise through contamination , breakage, evaporation, accidental scratching or bending, or improper or careless packaging. The use of latex gloves or disposable forceps when touching evidence often can prevent such problems. Any equipment that is not disposable should be cleaned and/or sanitized between collection of each piece of evidence. Evidence should remain unmoved until investigators have documented its location and appearance in notes, sketches, and photographs.

Evidence best maintains its integrity when kept in its original condition as it was found at the crime site. Whenever possible, one should submit intact evidence to the laboratory. The investigator normally should not remove blood, hairs, fi bers, soil

particles, or other types of trace evidence from garments, weapons, or any other articles that bear them. Instead, he or she should send the entire object to the laboratory for processing.

Of course, if evidence is adhering to an object in a precarious manner, good judgment dictates removing and packaging the item. Investigators must use common sense when handling evidence adhering to a large structure, such as a door, wall, or fl oor; they should remove the specimen with a forceps or other appropriate tool. In the case of a bloodstain, the investigator may either scrape the stain off the surface, transfer the stain to a moistened swab, or cut out the area of the object bearing the stain.

PACKAGING EVIDENCE

The well-prepared evidence collector arrives at a crime scene with a large assortment of packaging materials and tools, ready to encounter any type of situation. Forceps and similar tools may be used to pick up small items. Unbreakable plastic pill bottles with pressure lids are excellent containers for hairs, glass, fi bers, and various other kinds of small or trace evidence. Alter- natively, manila envelopes, screw-cap glass vials, sealable plastic bags, and metal pillboxes are adequate containers for most trace evidence encountered at crime sites (see Figure 7 ). Charred debris recovered from the scene of a suspicious fi re must be sealed in an airtight container to prevent the evapora- tion of volatile petroleum residues. New paint cans or tightly sealed jars are recommended in such situations (see Figure 8 ).

Ordinary mailing envelopes should not be used as evidence containers, because powders and fi ne particles will leak out of their corners. Instead, small amounts of trace evidence can be conveniently packaged in a carefully folded paper, using what is known as a “druggist fold” (see Figure 9 ). This method

FIGURE 6 A vacuum sweeper attachment, constructed of clear plastic in two pieces that are joined by a threaded joint. A metal screen is mounted in one half to support a fi lter paper to collect debris. The unit attaches to the hose of the vacuum sweeper. After a designated area of the crime scene is vacuumed, the fi lter paper is removed and retained for laboratory examination. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

contamination The transfer of extraneous matter between the collector and the evidence or multiple pieces of evidence, producing tainted evidence that cannot be used in the subsequent investigation.

90

COLLECTION OF CRIME-SCENE EVIDENCE

consists of placing the evidence in the center of a piece of paper, folding one- third of the piece of paper over the middle third (and the evidence), folding the opposite end (one-third) over that, then repeating the process on the other two sides. After folding the paper in this manner, one should tuck the outside two fl aps into each other to produce a closed container that keeps the specimen from falling out.

Each different item or similar items collected at different locations should be placed in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

BIOLOGICAL MATERIALS Use only disposable tools to collect biological mate- rials for packaging. If biological materials such as blood are stored in airtight containers, the accumulation of moisture may encourage the growth of mold, which can destroy their evidential value. In these instances, wrapping paper, manila envelopes, or paper bags are the recommended packaging materials

FIGURE 7 (a) A manila evidence envelope, (b) metal pillboxes, and (c) a sealable plastic evidence bag. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

FIGURE 8 Airtight metal cans used to package arson evidence. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www .sirchie.com

FIGURE 9 A druggist fold is used to package paint transfer evidence. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

(a)

(c)

(b)

91

COLLECTION OF CRIME-SCENE EVIDENCE

(see Figure 10 ). As a matter of routine, all items possibly containing biological fl uid evidence should be air-dried and placed individually in separate paper bags to ensure a constant circulation of air around them. This will prevent the formation of mold and mildew. Paper packaging is easily written on, but seals may not be sturdy. Finally, place a red biohazard sticker on both the secured evidence bag and the property receipt to ensure all handlers will be aware the item is contaminated with biological fl uids, such as blood, saliva, or semen.

The evidence collector must handle all body fl uids and biologically stained materials as little as possible. All body fl uids must be assumed to be infectious, so investigators must wear disposable latex gloves while handling the evi- dence. Latex gloves also signifi cantly reduce the possibility that the evidence collector will contaminate the evidence. Investigators should change gloves frequently during the evidence-collection phase of the investigation. Safety and contamination considerations also dictate that evidence collectors wear face masks and shoe covers.

DNA EVIDENCE The advent of DNA analysis brought one of the most signifi - cant recent advances in crime-scene investigation. This technique is valuable for making it possible to identify suspects through detecting and analyzing minute quantities of DNA deposited on evidence as a result of contact with saliva, sweat, or skin cells. The search for DNA evidence should include any and all objects with which the suspect or victim may have come into bodily contact. Likely sources of DNA evidence include stamps and envelopes that have been licked, a cup or can that has touched a person’s lips, chewing gum, the sweatband of a hat, and a bedsheet containing dead skin cells.

One key concern during the collection of a DNA-containing specimen is contamination. Contamination—in this case, introducing foreign DNA—can occur from coughing or sneezing onto evidence during the collection process. Transfer of DNA can also occur when items of evidence are incorrectly placed in contact with each other during packaging. To prevent contamination, the evidence collector must wear a face mask and use disposable latex gloves and disposable forceps. The evidence collector may also consider wearing coveralls and shoe covers as an extra precaution to avoid contaminating DNA evidence.

Blood analysis has great evidential value when it allows the investigator to demonstrate a transfer between a victim and a suspect. For this reason, all clothing from both the victim and suspect should be collected and sent to the

FIGURE 10 Paper bags and manila envelopes are recommended evidence containers for biological evidence, especially objects suspected of containing blood and semen stains. Each object should be packaged in a separate bag or envelope. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

92

COLLECTION OF CRIME-SCENE EVIDENCE

laboratory for examination, even when the presence of blood on a garment does not appear obvious to the investigator. Laboratory search procedures are far more revealing and sensitive than any that can be conducted at the crime scene.

MAINTAINING THE CHAIN OF CUSTODY

Whenever evidence is presented in court as an exhibit, the investigator must establish continuity of possession, or the chain of custody . This means that he or she must account for every person who handled or examined the evidence. Failure to substantiate the evidence’s chain of custody may lead to serious questions regarding the authenticity and integrity of the evidence and the examinations of it. Adhering to standard procedures in recording the location of evidence, marking it for identifi cation, and properly completing evidence- submission forms for laboratory analysis are the best guarantee that the evidence will withstand inquiries about what happened to it from the time it was found to its presentation in court.

Once an investigator selects an evidence container, he or she must mark it for identifi cation. All evidence packages must be labeled, and their open- ings must be sealed with evidence tape (see Figure 11 ). Evidence contain- ers often have a preprinted identifi cation form for the evidence collector to fi ll out; otherwise, the collector must attach an evidence tag to the container (see Figure 12 ). The investigator who packaged the evidence must write his or her initials and the date on the evidence tape seal. Anyone who removes the evidence for further testing or observation at a later time should try to

chain of custody A list of all people who came into possession of an item of evidence.

FIGURE 11 Proper evidence tape seals on evidence in various packages. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

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avoid breaking the original seal if possible so that the information on the seal will not be lost. The person who reseals the packaging should record his or her initials and the date on the new seal.

At a minimum, the record of the evidence that is used to demonstrate chain of custody shows the collector’s initials, the location of the evidence, and the date of collection. Transfer of evidence to another individual or delivery to the laboratory must be recorded in notes and other appropriate forms (see Figure 13 ). In fact, ev- ery individual who possesses the evidence must main- tain a written record of its acquisition and disposition. Frequently, all of the individuals involved in the collec- tion and transportation of the evidence must testify in court. Thus, to avoid confusion and to retain complete control of the evidence at all times, the transfer of cus- tody should be kept to a minimum.

Failure to substantiate the evidence’s chain of cus- tody may lead to serious questions regarding the au-

thenticity and integrity of the evidence and the examinations performed on it. Adhering to standard procedures when recording the location of evidence, marking it for identifi cation, and properly completing evidence-submission forms for laboratory analysis is the best way to guarantee that the fi ndings will withstand inquiries about the integrity of the evidence. If a delay occurs

between the time evidence is collected and the time it is submit- ted to the forensic laboratory, the investigator must store the evidence in a secured area with only limited access by police per- sonnel (see Figure 14 ).

OBTAINING STANDARD/

REFERENCE SAMPLES

To examine evidence, whether soil, blood, glass, hair, or fi bers, often the forensic scientist must compare it with a sample of similar material whose origin is known. This is known as a

FIGURE 12 Examples of evidence tags that may be attached directly to the evidence. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

FIGURE 13 A chain of custody form is used to record the name of every person who handled or examined the collected evidence. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

FIGURE 14 An example of a secure evidence locker. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

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standard or reference sample . Although most investigators have little dif- fi culty recognizing and collecting relevant crime-scene evidence, few seem aware of the necessity and importance of providing the crime lab with a thorough sampling of standard/reference materials. Such materials may be obtained from the victim, a suspect, or other known sources. For instance, investigation of a hit-and-run incident might require the removal of stan- dard/reference paint from a suspect vehicle. This will permit its comparison to paint recovered at the scene.

The presence of standard/reference samples greatly facilitates the work of the forensic scientist. For example, hair found at a crime scene will be of optimum value only when compared to standard/reference hairs removed from the suspect and victim. Likewise, bloodstained evidence must be accompanied by a whole-blood or buccal swab standard/reference sample obtained from all relevant crime-scene participants. The quality and quantity of standard/ reference specimens often determines the evidential value of crime-scene evidence, and so must be treated with equal care.

Some types of evidence must also be accompanied by substrate controls . These are materials close to areas where physical evidence has been depos- ited. For example, an arson investigator who suspects that a surface has been exposed to an accelerant, such as gasoline, should collect a piece of the same surface material that he or she believes was not exposed to the accelerant. At the laboratory, forensic scientists will fi rst test the substrate control to see whether the nature of the surface itself will interfere with the procedures used to detect and identify accelerants. Another common example of a substrate control is a material containing a bloodstain. Unstained areas close to the stain may be sampled to determine whether this material can interfere with the interpretation of laboratory results. Thorough collection and proper packag- ing of standard/reference specimens and substrate controls are marks of a skilled investigator.

SUBMITTING EVIDENCE

Evidence is usually submitted to the laboratory either personally or by mail. Although most evidence can be shipped by mail, postal regulations restrict the shipment of certain chemicals and live ammunition and prohibit the mail- ing of explosives. In such situations, one should consult the laboratory to determine the disposition of these substances. One must also exercise care when packaging evidence in order to prevent breakage or other accidental destruction during transit to the laboratory (see Figure 15 ). If the evidence is delivered personally, the deliverer should be familiar with the case to facili- tate any discussions with laboratory personnel concerning specifi c aspects of the case.

Most laboratories require that an evidence-submission form accompany all submitted evidence (see Figure 16 ). The information on this form enables the laboratory analyst to make an intelligent and complete examination of the evidence. Providing a brief description of the case history is particularly important. This information allows the examiner to analyze the specimens in a logical sequence and make the proper comparisons; it also facilitates the search for trace quantities of evidence.

The submission form should specify the particular kind of examination requested for each type of evidence. However, the analyst is not bound to adhere strictly to the specifi c tests requested by the investigator. The discovery of new evidence may dictate changes in the tests required, or the analyst may fi nd the initial requests incomplete or not totally relevant to the case. Items submitted for examination should be packaged separately and each item should be assigned a number or letter. The evidence-submission form should

standard/reference sample Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence.

buccal swab A swab of the inner portion of the cheek; performed to collect cells for use in determining the DNA profi le of an individual.

substrate controls Surface material close to areas where physical evidence has been deposited.

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list the items and their identifying numbers or letters in an orderly and logical sequence.

Once evidence is received, it will undergo the requested tests and exami- nations. When a piece of evidence has been fully examined and tested, it must be submitted to long-term storage. The storage area and containers should be secure to prevent tampering and maintain the chain of custody.

Quick Review • Physical evidence includes any and all objects that can establish that a crime

has been committed or can link the crime and its victim or perpetrator. • Many items of evidence may be detected only through examination

of crime-scene materials at the crime laboratory. For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fi ngernail scrapings, in addition to more discern- able items.

• Each item of physical evidence collected at a crime scene must be placed in a separate, appropriate container to prevent damage through contact and cross-contamination.

• Investigators must maintain the chain of custody, a record for denoting the location of the evidence.

• Proper standard/reference samples must be collected at the crime scene and from appropriate subjects for comparison purposes in the laboratory. Substrate controls must also be collected.

• Typically, an evidence-submission form accompanies all evidence sub- mitted to the crime laboratory. The form lists each item submitted for examination.

FIGURE 15 Evidence that has been correctly packaged and labeled can be sent through the mail. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

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Ensuring Crime-Scene Safety * Safety is one of the most important responsibilities of an employee because it can affect one’s personal health. The employer can implement rules and regulations; educate employees about the standard operating procedures, also known as SOPs; and supply the proper equipment and resources, but it is the

*This section was contributed by and is used with the permission of Jan Johnson, Forensic Spe- cialist; Certifi ed IAI CSCSA; Retired State of Florida; Forensic Pieces, Inc., and Natalie M. Borgan, MS; Certifi ed IAI CCSI; Crime Scene Technician, Coral Gables Police Department.

FIGURE 16 An example of a properly completed evidence-submission form. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

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responsibility of the employee to enforce these safety standards in the fi eld. Standard operating procedures should be reviewed annually by all crime- scene employees, and the agency should retain a record of reviews, which documents the date at which each employee reviewed the standard operating procedures. Updates of current crime-scene safety regulations and education should be provided annually by a designated crime-scene safety coordinator. Health inspections should also be included in the job requirements of personnel who operate certain safety equipment used at the crime scenes. For example, before an employee can wear a respirator at crime scenes, a physical health examination is required, and a proper fi t must be ensured.

PERSONAL PROTECTIVE EQUIPMENT (PPE)

RESPIRATORY PROTECTION Respiratory protection is one of the most important types of personal protective equipment (PPE). Respiratory protec- tion can range from a disposable fi lter mask to a self-contained breathing apparatus, also known as SCBA. Every crime-scene unit should have a train- ing program that teaches employees about the different types of respiratory protection so they will be able to choose the mask that is most appropriate for each crime scene. The most important thing to remember when using a mask is to make sure it is properly sealed, which is the perfect fi t. A proper seal between the face and the respiratory mask prevents any chemicals or irritants from entering.

Crime-scene technicians or investigators should know the differences between the respiratory protections available for use at different crime-scene environments. Dust particle masks or N-95 masks are used for routine crime scenes. They are considered the most common type of respiratory protection. These masks are considered to be disposable and should be discarded after one use. The half-face cartridge respirator can be a disposable model with a mechanical fi lter or a reusable model with disposable fi lters. It is called a half- face cartridge respirator because it protects only the bottom half of the face, including the mouth and nose. A power-assisted air-purifying respirator is a positive-pressure system, which means that the air on the inside of the mask is at a higher pressure than the outside air pressure. This type of respira- tor allows the wearer to control the air that passes through the respirator to reduce or increase the amount of air that is fi ltered. Full-face respirators cover the entire face to protect the face and eyes from contaminants while fi ltering the air. This type of mask works well to fi lter contaminants, such as chemicals, dust, and spores, from the air the wearer breathes. First responders and fi re- fi ghters especially benefi t from these masks because they are in contact with hazardous chemicals on a daily basis.

A self-contained breathing apparatus has a tank, a regulator, and inha- lation piece. If someone is claustrophobic, he or she would have a problem utilizing one of these respirators. Not all crime-scene personnel will be able to wear an SCBA. Investigators must fi rst undergo a health screening to detect possible lung issues.

EYE PROTECTION Eye protection is extremely important when a crime-scene worker is processing a crime scene where contaminants or chemicals could get into his or her eyes. The crime-scene technician must wear goggles even if he or she is wearing prescription glasses or contacts; glasses or contacts do not replace proper eye protection. If your eye comes into contact with a chem- ical, rinse your eye with water for a minimum of 15 minutes. Chemical goggles are the best type of goggles. Face shields are also considered eye protection, and goggles must be worn with them. If any type of laser is being used at the crime scene, workers should wear the appropriate eye protection.

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CHEMICAL PROTECTIVE CLOTHING Tyvek protective clothing is inexpensive, chemical resistant, and disposable. Tyvek is diffi cult to tear but easy to cut. In extreme temperatures, Tyvek should not be worn for longer than 15 minutes at a time: Because the material traps heat, the wearer must take a break from the Tyvek to allow his or her body to readjust to the ambient temperature. If the rest period is not provided, heat stroke and possible death may occur. Nomex brand protective clothing is fi re retardant but not fi reproof; it can only resist fl ames of up to approximately 220 degrees Celsius. Neoprene protective clothing has good chemical stability and is chemical resistant and waterproof. It is widely used and inexpensive. Butyl rubber is a synthetic rubber that is a harder and less porous material than natural rubber, and although it is expensive, it is used in boots, aprons, and gloves. Saranex material is chemical resistant and dispos- able. However, workers need to be careful in hot conditions because heat stress can quickly become a serious problem when wearing this material.

Hand protection helps the crime-scene worker to avoid destroying and/ or contaminating evidence while protecting him or her from safety hazards. Gloves are essential when processing crime scenes. However, a crime-scene technician or investigator needs to know the different types of gloves avail- able and, after assessing the situation, which will be the best for processing the scene. Gloves should be changed on a frequent basis during crime-scene processing, especially when a glove has become soiled or to avoid cross- contamination when the investigator is about to collect a different piece of evidence. Because gloves degrade over time, when gloves are purchased, the box should be dated and the box with the oldest date should be used up fi rst. Gloves will also degrade in extreme temperatures.

Polyvinyl gloves are thin, clear gloves that don’t provide any protection against chemicals or acids. These gloves are fi ne for processing crime scenes with black powder and biological fl uids. Latex gloves are especially good for processing scenes with black powder and biological fl uids. Because this type of glove is thin, gloves must discarded after a single use. Latex is a relatively weak material, and the wearer must be alert for any pinholes, which can undermine the integrity of the glove. It is not a bad idea to “double glove” when using latex gloves, but this will not resolve the pinhole problem. There are individuals who are latex sensitive and therefore need to use a different type of glove to avoid an allergic reaction. Allergic reactions should be taken seriously; they can result in serious injury or even be fatal. Even exposure to another crime-scene investigator who is wearing latex can cause an allergic response in those allergic to latex.

Nitrile gloves are better than latex gloves and provide more protection. These gloves are inexpensive and resistant to some chemicals. Neoprene gloves are chemical resistant and must be worn when processing scenes with chemicals, such as acids and alcohol. At the crime scene, gloves should be changed often, and all contaminated protective gear should be removed and disposed of in biohazard bags.

By wearing shoe covers, the investigator will avoid creating new foot tracks at the crime scene. It should be a standard rule for investigators repond- ing to crime scenes with a substantial amount of blood or biological fl uids to wear foot protection, such as shoe covers or booties. The different types of foot protection include disposable Tyvek shoe covers with vinyl soles, dispos- able Tyvek high-top boots with vinyl soles, and disposable rubber shoe covers. Tyvek shoe covers are made to be strong and tear resistant. However, rubber shoe covers would be necessary at chemical crime scenes, such as clandestine labs. The benefi ts of rubber shoe covers are that they won’t conduct electricity and are excellent to wear in wet environments. Alternatively, an investigator or technician can purchase and wear inexpensive new shoes and dispose of the contaminated shoes after processing the crime scene.

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An investigator may expose children and pets to diseases by walking in biological fl uids at a crime scene and then walking around in his or her resi- dence with the same contaminated shoes. A crime-scene worker must have personal rules such as always leaving work shoes at the front door of his or her residence. If you set personal rules from the beginning, you can prevent contaminates from coming home with you. All nondisposable items such as lab coats, towels, and personal clothing that may be contaminated with potentially infectious material should be placed in a yellow plastic bag labeled “Infectious Linen” and laundered, at the expense of the employer, by a qualifi ed laundry service. Personal clothing that may have been contaminated should never be taken home for cleaning. If a qualifi ed laundry service for “Infectious Linen” is not available to the agency, these nondisposable items should be placed in a red plastic bag and labeled “Biohazard Material.” These items will need to be destroyed because they may contain infectious material.

BIOLOGICAL HAZARDS

UNIVERSAL PRECAUTIONS AND BLOODBORNE PATHOGENS It is extremely important for every crime-scene technician to comprehend and apply the Universal Precaution Rule, which states that when an individual responds to a crime scene that has blood or tissue, he or she must assume the blood or tissue sample is infected and treat the sample as if it contains an infectious disease such as hepatitis B, hepatitis C, human immunodefi ciency virus (HIV), or any number of other infectious agents. Make sure you wear your appropriate PPE, such as a mask and gloves, when working at a bloody crime scene or one involving biological fl uids or tissue.

In general, all of the infectious viruses (hepatitis B, hepatitis C, and HIV) are composed of either DNA or RNA viruses that have the ability to infect humans by a number of different exposure routes. Whether the exposure is by an accidental stick from a needle or knife or broken glass or some other hazard at the crime scene or the laboratory, there is the possibility of acquiring an infection. Even indirect exposures caused by sloppy techniques such as talking on a cell phone while working in the hot zone may introduce the virus to the mucus membranes of your mouth or eyes. To prevent possible health hazards, a clean mask and gloves should be worn in the event a cell phone must be used at the scene.

It is not uncommon for both hepatic viruses to be present in a contaminating source, along with the HIV virus. There are numerous stages and clinical presentations that an individual with hepatitis can exhibit, and the ultimate outcome of hepatitis is quite variable and beyond the scope of this chapter. It is important to remember that the best treatment regarding exposure to blood-borne pathogens is prevention. Every crime scene technician should be vaccinated for hepatitis to avoid contracting these diseases in the event of an accidental exposure. The hepatitis immunization consists of three shots over a nine- to twelve-month period and should be effective for fi fteen to twenty years.

In general, not every exposure to infected blood or bodily fl uid will result in your acquiring an infection and the disease. Numerous factors, including the viral load of the infected material or fl uid, the promptness and thorough- ness of cleaning the site of the exposure (cuts or scraps or splashes), the route of exposure, and the immune system of the exposed individual, all play a vital role in whether or not one will become infected.

If a piece of physical evidence is wet from blood, place the piece of evidence in a paper bag—even consider double-bagging the item with two brown paper bags to keep the outside bag free of contamination—and then place it in a red biohazard bag for transportation to the crime lab. Then, you can use the appropriate drying cabinet to let your evidence air dry before

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putting it in the property room. Remember to place a piece of butcher paper on the bottom of the drying cabinet in case any evidence falls off the item onto the butcher paper during the drying process. The original paper bag and the butcher paper should be kept and stored for possible analysis. After the contaminated bloody evidence has completely dried, use butcher paper to fold the item to avoid creating new patterns on the item, then place it in a new paper bag. Always remember to place a red biohazard sticker both on the fi nal, secured evidence bag and the property receipt to ensure all handlers will know the item is contaminated with biological fl uids.

DIFFERENT TYPES OF EXPOSURE

AT CRIME SCENES

When an investigator responds to a crime scene, there are several different ways in which he or she can be exposed to toxins. If crime-scene personnel are trained and educated to identify these means of exposure, they can protect themselves with the proper personal protection equipment. Among the contaminants that can be present at a crime scene are various chemicals, gas, fumes, dust, and powders, and the only way to avoid exposure is by using the proper PPE.

ABSORPTION Absorption occurs when contaminants make contact with skin or absorb through mucus membrane areas, such as nostrils, mouth, and eyes. Also, contaminants can absorb readily through an unprotected cut on the skin, which is an easy point of entry. If contaminants come into contact with your eyes, rinse your eyes with water for a minimum of fi fteen minutes. Portable eyewash stations should be part of the crime-scene safety equipment.

INGESTION Ingestion occurs when contaminants enter the body through the mouth. An individual must be careful when considering drinking or eating at a crime scene to prevent ingestion of chemicals. The “cold zone,” a work area described in detail in the following section, should be the only area within the crime scene where drinking and eating take place. Chewing gum is another way to ingest such toxins at the crime scene and should be considered taboo.

INHALATION Inhalation occurs when contaminants enter the body through the respiratory system. When an investigator or technician responds to a crime scene, he or she must assess the scene to determine which respiratory mask will offer the best protection from the contaminants present.

INJECTION An injection can enter the body in the form of a needle or sharp object. When working with needles or sharp objects, such as pieces of glass, an individual should wear proper gloves for protection and use special care to prevent being poked by sharp objects. Crime-scene personnel should take their time to be safe when processing all sharp objects, especially needles. They must also be mindful of how they package such objects for others who will receive the evidence and may not know of the inherent risks of handling it.

WORK ZONES

The “hot zone” is the active crime-scene area, which means contaminates and probable evidence exists in this region. In the hot zone, all crime-scene technicians should be suited up with PPE, such as masks, foot protection, eye protection, and gloves. There should be no food or drinks allowed in the hot zone. Also, the employees who are actively working the crime scene should be the only ones allowed in this area. The warm zone is the transition area between the cold and hot zones. This is the area where the crime-scene techni- cians will suit up with their PPE, and it is the staging area for the equipment.

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After the crime-scene processing is complete, the warm zone should also be the decontamination area used to prevent spreading any contamination. When potentially infectious materials are present at a crime scene, personnel should maintain a red biohazard plastic bag for the disposal of contaminated gloves, clothing, masks, pencils, wrapping paper, and so on. On departure from the scene, the biohazard bag must be taped shut and transported to an approved biohazardous waste pickup site. The cold zone is the safe area for all personnel who were not actively processing the scene. The fi rst offi cer on the scene should be using this area to write down the names of the individuals entering and exiting the actual crime scene, or hot zone. The cold zone is also the area where employees can take breaks, eat, and drink. Every crime-scene technician should understand the importance of establishing and maintaining these separate work zones in scenes where contaminants are present. When traveling from the hot zone to the cold zone, decontaminating in the warm zone is essential.

Not every crime scene requires that work zones be established for safety. Simple cases such as burglaries and car thefts do not require zone assignments. Obviously, homicides and other crime scenes that contain bodily fl uids and/or contaminants do require the establishment of work zones. The normal precautions of wearing gloves and masks and the like are more than suffi cient for low-risk crime scenes. When responding to crime scenes that are contaminated, personnel need to know which zones are active, such as hot zone, warm zone, and cold zone, and therefore these zones need to be clearly delineated by the investigator so that personnel do not cross them in an unprotected state.

Quick Review • Updates of current crime-scene safety regulations and education should

be made annually by a designated crime-scene safety coordinator. Health inspections should also be included in the job requirements of personnel who operate certain safety equipment used at the crime scenes.

• Law enforcement offi cers and crime-scene technicians at a crime scene must use caution and protect themselves at all times from contracting AIDS or hepatitis. Bodily fl uids must always be treated as though they were infectious.

• Crime-scene technicians most often use dust particle masks or N-95 masks at routine crime scenes. They are considered the most common type of respiratory protection. These masks are considered to be disposable and should be discarded after one use.

• It is recommended that personnel always wear doubled-up latex gloves and possibly wear chemical-resistant clothing, Tyvek-type shoe covers, a particle mask/respirator, goggles, and possibly face shields when poten- tially infectious material is present. Gloves should be changed often while processing the scene.

• When processing and collecting evidence at a crime scene, person- nel should be alert to sharp objects, knives, hypodermic syringes, razor blades, and similar items.

• Eating, drinking, smoking, eating, and chewing gum are prohibited at the immediate crime scene.

• The hot zone is the active crime-scene area, which means contaminates and probable evidence exists in this region. In the hot zone, all crime-scene technicians or investigators should be suited up with personal protection equipment, also known as PPE, such as masks, foot protection, eye protec- tion, and gloves. No food or drinks should be allowed in the hot zone.

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Legal Considerations at the Crime Scene In police work, there is perhaps no experience more exasperating or demoral- izing than to watch valuable evidence excluded from use against the accused because of legal considerations. This situation most often arises from what is deemed an “unreasonable” search and seizure of evidence. Therefore, the removal of any evidence from a person or from the scene of a crime must be done in conformity with the Fourth Amendment: “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affi rmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Since the 1960s, the Supreme Court of the United States has been par- ticularly concerned with defi ning the circumstances under which the police can search for evidence in the absence of a court-approved search warrant. The court has made a number of allowances to justify a warrantless search: (1) the existence of emergency circumstances, (2) the need to prevent the immediate loss or destruction of evidence, (3) a search of a person and property within the immediate control of the person provided it is made incident to a lawful arrest, and (4) a search made by consent of the parties involved. In cases other than these, police must be particularly cautious about process- ing a crime scene without a search warrant. In 1978, the Supreme Court ad- dressed this very issue, and in doing so it set forth guidelines for investigators to follow in determining the propriety of conducting a warrantless search at a crime scene. Signifi cantly, the two cases decided on this issue related to homi- cide and arson crime scenes, both of which are normally subjected to the most intensive forms of physical evidence searches by police.

In the case of Mincey v. Arizona, 1 the Court dealt with the legality of a four-day search at a homicide scene. The case involved a police raid on the home of Rufus Mincey, who had been suspected of dealing drugs. Under the pretext of buying drugs, an undercover police offi cer forced entry into Mincey’s apartment and was killed in the scuffl e that ensued. Without a search warrant, the police spent four days searching the apartment, recovering, among other things, bullets, drugs, and drug paraphernalia. These items were subsequently introduced as evidence at the trial. Mincey was convicted and on appeal contended that the evidence gathered from his apartment, without a warrant and without his consent, was illegally seized. The Court unanimously upheld Mincey’s position, stating:

We do not question the right of the police to respond to emergency situations. Numerous state and federal cases have recognized that the Fourth Amendment does not bar police offi cers from making warrantless entries and searches when they reasonably believe that a person within is in need of immediate aid. Similarly, when the police come upon the scene of a homicide they may make a prompt warrantless search of the area to see if there are other victims or if a killer is still on the premises. . . . Except for the fact that the offense under investigation was a homicide, there were no exigent circumstances in this case. . . . There was no indi- cation that evidence would be lost, destroyed or removed during the time required to obtain a search warrant. Indeed, the police guard at the apartment minimized that possibility. And there is no suggestion that a search warrant could not easily and conveniently have been obtained. We decline to hold that the seriousness of the offense under investigation itself creates exigent circumstances of the kind that under the Fourth Amendment justify a warrantless search.

In Michigan v. Tyler, 2 fi re destroyed a business establishment leased by Loren Tyler and a business partner. The fi re was fi nally extinguished in the

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early hours of the morning; smoke, steam, and darkness, however, prevented fi re and police offi cials from thoroughly examining the scene for evidence of arson. Offi cials then left the building unattended until eight a.m. that morn- ing, when they returned and began an inspection of the burned premises. During the morning, searchers recovered and removed assorted items of evi- dence from the building. On three other occasions—four days, seven days, and twenty-fi ve days after the fi re—investigators reentered the premises and removed additional items of evidence with neither a warrant nor consent. The evidence seized was used to convict Tyler and his partner of conspiracy to burn real property and related offenses. The Supreme Court upheld the rever- sal of the conviction, holding that the initial morning search had been proper but contending that evidence obtained from subsequent reentries to the scene was inadmissible: “We hold that an entry to fi ght a fi re requires no warrant, and that once in the building, offi cials may remain there for a reasonable time to investigate the cause of a blaze. Thereafter, additional entries to investigate the cause of the fi re must be made pursuant to the warrant procedures.”

The message from the Supreme Court is clear: When time and circum- stances permit, obtain a search warrant before investigating and retrieving physical evidence at the crime scene.

Quick Review • The removal of any evidence from a person or from the scene of a crime

must be in accordance with proper search and seizure procedure. • Warrantless searches are allowed in situations including (1) the existence

of emergency circumstances, (2) the need to prevent the immediate loss or destruction of evidence, (3) a search of a person and property within the immediate control of the person provided it is made incident to a lawful arrest, and (4) a search made with the consent of the parties involved.

CHAPTER REVIEW

• Biological crime-scene evidence includes blood, saliva, semen, DNA, hair, organs, and physiological fl uids.

• Impression crime-scene evidence includes tire markings, shoe prints, depressions in soft soils, all other forms of tracks, glove and other fabric impressions, tool marks, and bite marks.

• Manufactured items considered common items of crime- scene evidence include fi rearms, ammunition, fi bers, paint, glass, petroleum products, plastic bags, rubber, polymers, and vehicle headlights.

• Physical evidence includes any and all objects that can estab- lish that a crime has been committed or can link the crime and its victim or perpetrator.

• Many items of evidence may be detected only through examination of crime-scene materials at the crime labora- tory. For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fi ngernail scrapings, in addition to more discernable items.

• Each item of physical evidence collected at a crime scene must be placed in a separate, appropriate container to pre- vent damage through contact and cross-contamination.

• Investigators must maintain the chain of custody, a record for denoting the location of the evidence.

• Proper standard/reference samples must be collected at the crime scene and from appropriate subjects for comparison purposes in the laboratory. Substrate controls must also be collected.

• Typically, an evidence-submission form accompanies all evidence submitted to the crime laboratory. The form lists each item submitted for examination.

• Updates of current crime scene safety regulations and educa- tion should be made annually by a designated crime scene safety coordinator. Health inspections should also be included in the job requirements of personnel who operate certain safety equipment used at the crime scenes.

• Law enforcement offi cers and crime-scene technicians must use caution and protect themselves at all times from contracting AIDS or hepatitis. Bodily fl uids must always be treated as though they were infectious.

• Crime-scene technicians most often use dust particle masks or N-95 masks at routine crime scenes. They are considered

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KEY TERMS

the most common type of respiratory protection. These masks are considered to be disposable and should be discarded after one use.

• It is recommended that personnel always wear doubled-up latex gloves and possibly wear chemical-resistant clothing, Tyvek-type shoe covers, a particle mask/respirator, goggles, and possibly face shields when potentially infectious material is present. Gloves should be changed often while processing the scene.

• When processing and collecting evidence at a crime scene, personnel should be alert to sharp objects, knives, hypoder- mic syringes, razor blades, and similar items.

• Eating, drinking, smoking, eating, and chewing gum are prohibited at the immediate crime scene.

• The hot zone is the active crime-scene area, which means contaminates and probable evidence exists in this region.

In the hot zone, all crime-scene technicians or investigators should be suited up with personal protection equipment, also known as PPE, such as masks, foot protection, eye protection, and gloves. No food or drinks should be allowed in the hot zone.

• The removal of any evidence from a person or from the scene of a crime must be in accordance with proper search and seizure procedure.

• Warrantless searches are allowed in situations including (1)  the existence of emergency circumstances, (2) the need to prevent the immediate loss or destruction of evidence, (3) a search of a person and property within the immediate control of the person provided it is made incident to a lawful arrest, and (4) a search made with the consent of the parties involved.

buccal swab

chain of custody

contamination

physical evidence

standard/reference sample

substrate control

REVIEW QUESTIONS

1. The term ______________ encompasses all objects that can establish whether a crime has been committed or can link a crime and its victim or perpetrator.

2. True or False: The well-prepared evidence collector arrives at a crime scene with a large assortment of packaging materials and tools ready to encounter any type of situation. ______________

3. The ______________ purchased by some police depart- ments for evidence collection carry the necessary supplies to protect the crime scene; photograph, collect, and package physical evidence; and perform latent-print development.

4. Because some items of evidence may be detected only through examination of crime-scene materials in the crime laboratory, it is important to collect all potential ______________ of physical evidence.

5. True or False: Critical areas of the crime scene should be vacuumed and the sweepings submitted to the laboratory for analysis. ______________

6. An individual may have hand contact with the skin of another individual during the commission of a crime, so ______________ scrapings should be collected because they may contain minute fragments of evidence capable of providing a link between assailant and victim.

7. True or False: The problems of contamination can often be avoided through the use of latex gloves or disposable forceps when touching evidence. ______________

8. True or False: Whenever possible, trace evidence is to be removed from the object that bears it. ______________

9. Each item collected at the crime scene must be placed in a(n) ______________ container.

10. True or False: Unbreakable plastic pill bottles, manila enve- lopes, screw-cap glass vials, sealable plastic bags, and metal pillboxes with pressure lids are excellent containers for blood or arson evidence. ______________

11. True or False: An ordinary mailing envelope is considered a good general-purpose evidence container. ______________

12. True or False: Charred debris recovered from the scene of an arson is best placed in a porous container. ______________

13. Small amounts of trace evidence can also be conveniently packaged in a(n) ______________ , a carefully folded paper packet.

14. Only ______________ tools should be used to collect biological materials for packaging.

15. Packaging material for biological evidence, including blood- stained evidence, should be made of ______________ to ensure a constant circulation of air through them.

16. ______________ of DNA-containing evidence can easily occur by coughing or sneezing onto a stain during the collec- tion process or by contact caused by improper packaging.

17. As a matter of routine, all moist biological stains are to be ______________ before packaging.

18. The possibility of future legal proceedings requires that a(n) ______________ be established with respect to the posses- sion and location of all physical evidence.

105

APPLICATION AND CRITICAL THINKING

ENDNOTES

1. Offi cer Martin Guajardo is the fi rst responder at an appar- ent homicide scene. After securing the area, interviewing the sole witness, and calling for backup, he begins to search for evidence. He makes note of a bloody knife lying next to the body. A small scrap of bloody cloth is clinging precariously to the knife. Because it is a very windy day, Offi cer Guajardo removes the scrap of fabric and seals it in a plastic bag. A few moments later, the crime-scene team, including a photogra- pher, arrives to take over the investigation. What mistakes, if any, did Offi cer Guajardo make prior to the arrival of the crime-scene team?

2. During his search of a homicide scene, investigator David Gurney collects evidence that includes a bloody shirt. After the crime-scene team has completely processed the scene, Investigator Gurney packages the shirt in a paper bag, seals the bag, and labels it to indicate the contents. He then deliv- ers the shirt to the laboratory with an evidence-submission form. There, a forensic scientist breaks the seal, removes the shirt, and performs a series of tests on it. He replaces the shirt, discards the old seal, and places a new seal on the package containing his initials and the date on which it was resealed. What mistakes, if any, were made in handling the shirt?

1. 437 U.S. 385 (1978).

2. 436 U.S. 499 (1978).

19. True or False: The investigator who packaged the evi- dence must write his or her initials and the date on the evidence tape seal, and the evidence should be opened at a different location on the packaging for further testing. ______________

20. Most physical evidence collected at the crime site will require the accompanying submission of ______________ material for comparison purposes.

21. Blood evidence should be accompanied by known controls in the form of whole blood or ______________ from victims or suspects.

22. Uncontaminated areas close to where bloodstains were de- posited are called ______________ and should be collected from the crime scene.

23. True or False: Evidence is usually submitted to the labora- tory either personally or by mail depending on the distance the submitting agency must travel to the laboratory and the urgency of the case. ______________

24. A(n) ______________ form accompanies all evidence submitted to the laboratory and delineates the examination requested for each item of evidence.

25. Although the chance of law enforcement offi cers contracting AIDS or hepatitis at the crime scene is low, bodily fl uids must always be treated as though they are ______________ .

26. At the crime scene, latex gloves should be changed often, and all contaminated protective gear should be removed and disposed of in ______________ bags.

27. True or False: The removal of any evidence from a person must be done in accordance with proper search and seizure procedure, but it is not required for removal of crime-scene evidence. ______________

28. In the case of Mincey v. Arizona , the Supreme Court restricted the practice of conducting a(n) ______________ search at a homicide scene.

29. In the case of Michigan v. Tyler , the Supreme Court dealt with search and seizure procedures at a(n) ______________ scene.

COLLECTION OF CRIME-SCENE EVIDENCE

106

THE GRIM SLEEPER The killing spree began in 1985 in Los Angeles, California, and apparently ended in 1988. All but one of the serial killer’s eight victims were black females. Many of his victims were prostitutes with whom he would have sexual contact before strangling or shooting them. In 2002, the killing resumed. The attacker was dubbed the

“Grim Sleeper” because he appeared to have taken a fourteen-year hiatus from his crimes. By 2007, three more females were added to his list of victims. What proved particularly frustrating to investi- gators was that, even though this killer left behind DNA evidence at many of his crime scenes, a search of the DNA data- bases proved fruitless in establishing an identifi cation. If the killer had been con- victed of criminal activities in the past, they never resulted in the collection of his DNA and its placement in the California database. Finally, in 2010, police arrested and identifi ed Lonnie David Franklin Jr. as the Grim Sleeper. The arrest of Franklin came about through a familial DNA search, which trolls through the DNA database looking for partial DNA matches that could be linked to a close relative in the fi le. One prisoner— Franklin’s son

Christopher—shared a strong familial pattern with the serial killer. Investigators used DNA collected off a dis- carded pizza crust eaten  by Lonnie Franklin to link his DNA to the Grim Sleeper’s victims.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Explain the difference between the identifi cation

and comparison of physical evidence. • Defi ne and contrast individual and class characteristics of

physical evidence. • Appreciate the value of class evidence as it relates

to a criminal investigation. • List and explain the function of national databases available

to forensic scientists.

Physical

Evidence

AP Photo/Nick Ut

From Chapter 5 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

PHYSICAL EVIDENCE

Examination of Physical Evidence Physical evidence is usually examined by a forensic scientist for identifi cation or comparison.

IDENTIFICATION

The purpose of identifi cation is to determine the physical or chemical iden- tity of a substance with the most certainty that existing analytical techniques will permit. For example, the crime laboratory is frequently asked to identify the chemical composition of preparations that may contain illicit drugs such as heroin, cocaine, or barbiturates. It may be asked to identify gasoline in residues recovered from the debris of a fi re, or it may have to identify the nature of explosive residues—for example, dynamite or TNT. Also, the identi- fi cation of blood, semen, hair, or wood would, as a matter of routine, include a determination of species origin. For example, did a bloodstain originate from a human or a dog or cat? Each of these requests requires the analysis and ultimate identifi cation of a specifi c physical or chemical substance to the exclusion of all other possible substances.

The process of identifi cation fi rst requires adopting testing procedures that give characteristic results for specifi c standard materials. Once these test results have been established, they may be permanently recorded and used repeatedly to prove the identity of suspect materials. For example, to ascertain that a particular suspect powder is heroin, the test results on the powder must be identical to those that have been previously obtained from a known heroin sample.

Second, identifi cation requires that the number and type of tests used to identify a substance be suffi cient to exclude all other substances. This means that the examiner must devise a specifi c analytical scheme that will eliminate all but one substance from consideration. Hence, if the examiner concludes that a white powder contains heroin, the test results must have been compre- hensive enough to have excluded all other drugs—or, for that matter, all other substances—from consideration.

Simple rules cannot be devised for defi ning what constitutes a thorough and foolproof analytical scheme. Obviously, each type of evidence requires a unique test, and each test has a different degree of specifi city. Thus, one substance could conceivably be identifi ed by one test, whereas another may require the combination of fi ve or six different tests to arrive at an identifi ca- tion. Because the foresic scientist has little or no control over the quality and quantity of the specimens received, a standard series of tests cannot prevent all possible problems and pitfalls. So the forensic scientist must determine at what point the analysis can be concluded and when the criteria for positive identifi cation has been satisfi ed; for this, he or she must rely on knowledge gained through education and experience. Ultimately, the conclusion will have to be substantiated beyond any reasonable doubt in a court of law.

COMPARISON

A comparison analysis subjects a suspect specimen and a standard, or refer- ence, specimen to the same tests and examinations to ultimately determine whether they have a common origin. For example, the forensic scientist may link a suspect to a particular location by noting the similarities of a hair found at the crime scene to hairs removed from the suspect’s head (see Figure 1 ). Or a paint chip found on a hit-and-run victim’s garment may be compared with paint removed from a vehicle suspected of being involved in the incident.

identifi cation The process of determining a substance’s physical or chemical identity.

comparison The process of ascertaining whether two or more objects have a common origin.

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PHYSICAL EVIDENCE

The forensic comparison is actually a two-step procedure. First, combinations of select properties are chosen from the suspect and the standard/reference specimen for comparison. The question of which and how many properties are selected depends on the type of materials being examined. The overriding consideration must be the ultimate evidential value the conclusion will have.

Once the examination has been completed, the forensic scientist must draw a conclusion about the origins of the specimens. Reaching this conclusion is the second objective. Do they come from the same source or not? Certainly, if one or more of the properties selected for comparison do not agree, the analyst will conclude that the specimens are not the same and therefore could not have originated from the same source. Suppose, on the other hand, that all the properties do compare and the specimens, as far as the examiner can determine, are indistinguishable. Does it logically follow that they came from the same source? Not necessarily.

To comprehend the evidential value of a comparison, one must appreciate the role that probability has in ascertaining the origins of two or more specimens. Simply defi ned, probability is the frequency of occurrences of an event. If a coin is fl ipped a hundred times, in theory we can expect heads to come up fi fty times. Hence, the probability of the event (heads) occurring is fi fty in one hundred. In this case, probability is the odds that a certain match will occur when two specimens are compared.

INDIVIDUAL CHARACTERISTICS Evidence that can be associated with a unique common source with an extremely high degree of probability is said to possess individual characteristics . Examples of such associations are the matching ridge characteristics of two fi ngerprints, matching random striations (markings) on bullets or tool marks, matching irregular and random

FIGURE 1 A side-by-side comparison of hairs. Courtesy Chris Palenik, Microtrace LLC, Elgin, IL, www.microtracescientifi c.com

individual characteristics Properties of evidence that can be attributed to a particular source with an extremely high degree of certainty.

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PHYSICAL EVIDENCE

wear patterns in tire or footwear impressions, consistent handwriting characteristics, the fi tting together of the irregular edges of broken objects in the manner of a jigsaw puzzle (see Figure 2 ), or matching striation marks run- ning across plastic bags that were made sequentially (see Figure 3 ).

FIGURE 2 The body of a woman was found with evidence of beating about the head and a stablike wound in the neck. Her husband was charged with the murder. The pathologist found a knife blade tip in the wound in the neck. The knife blade tip was compared with the broken blade of a penknife found in the trousers pocket of the accused. Note that, in addition to the fi t of the indentations on the edges, the scratch marks running across the blade tip correspond in detail to those on the broken blade. Courtesy Centre of Forensic Sciences, Ministry of Community Safety and Correctional Services, Toronto, Canada

FIGURE 3 The bound body of a young woman was recovered from a river. Her head was covered with a black polyethylene trash bag (shown on the right). Among the items recovered from one of several suspects was another black polyethylene trash bag (shown on the left). A side-by-side comparison of the two bags’ extrusion marks and pigment bands showed them to be consecutively manufactured. This information allowed investigators to focus their attention on one suspect, who ultimately was convicted of the homicide. Courtesy George W. Neighbor

110

PHYSICAL EVIDENCE

In all of these cases, it is not possible to state with mathematical exactness the probability that the specimens are of common origin; it can be concluded only that the probability is so high as to defy mathematical calculations or human comprehension. Furthermore, the conclusion of common origin must be substantiated by the practical experience of the examiner. For example, the French scientist Victor Balthazard determined mathematically that the  probability of two individuals having the same fi ngerprints is one out of 1 � 10 60 , or 1 followed by sixty zeros. This probability is so small as to exclude the possibility of any two individuals having the same fi ngerprints. This contention is supported by the experience of fi ngerprint examiners who, after classifying millions of prints over the past hundred years, have never found any two to be exactly alike.

CLASS CHARACTERISTICS One disappointment awaiting the investigator unfamiliar with the limitations of forensic science is the frequent inability of the laboratory to relate physical evidence to a common origin with a high degree of certainty. Evidence is said to possess class characteristics when it can be associated only with a group and not with a single source. Here again, probability is a determining factor. For example, if we compare two single-layer automobile paint chips of a similar color, their chance of originating from the same car is not nearly as great as when we compare two paint chips with seven similar layers of paint, not all of which were part of the car’s original color. The former will have class characteristics and can be associated with, at the most specifi c, one car model (which may number in the thousands); the latter may be judged to have individual characteristics and thus has a high probability of originating from one specifi c car.

Blood offers another good example of evidence that can have class char- acteristics. For example, suppose that two blood specimens are compared and both are found to be of human origin, type A. The frequency of occurrence of type A blood in the US population is approximately 26 percent—hardly a basis for establishing the common origin of the specimens. However, if other blood factors are also determined and are found to compare, the probability that the two blood specimens originated from a common source increases. Thus, if one uses a series of blood factors that occur independently of each other, then one can apply the product rule to calculate the overall frequency of occurrence of the blood in a population. In this case, the product rule states that multiplying together the frequency of each factor present and occurring independently in a blood sample will determine how common blood contain- ing that combination of factors is in the general population.

For example, in the O. J. Simpson murder case, a bloodstain located at the crime scene was found to contain a number of factors that compared to O. J.’s blood:

Blood Factors Frequency

A 26%

EsD 85%

PGM 2�2� 2%

The product of all the frequencies shown in the table determines the prob- ability that any one individual possesses such a combination of blood factors. In this instance, applying the product rule, 0.26 � 0.85 � 0.02 equals 0.0044. Thus, only 0.44 percent, or less than 1 in 200 people, would be expected to have this particular combination of blood factors. These bloodstain factors did not match either of the two victims, Nicole Brown Simpson or Ronald Goldman, thus eliminating them as possible sources of the blood. Although the forensic

class characteristics Properties of evidence that can be associated only with a group and not with a single source.

product rule A formula for determining how frequently a certain combination of characteristics occurs in a population. The product rule states that one must fi rst determine the probability of each characteristic’s occurring separately and indepentently, then multiply together the frequencies of all these independently occurring characteristics. The result is the overall frequency of occurrence for that particular combination of characteristics.

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PHYSICAL EVIDENCE

scientist did not defi nitively link the bloodstains to one person (in this case, O.  J. Simpson), this analysis provided data that permitted investigators and the courts to better assess the evidential value of the crime-scene stain.

T he product rule is used to determine the frequency of occurrence of DNA profi les developed from blood and other biological materials. Importantly, modern DNA technology provides enough factors to allow an analyst to indi- vidualize blood, semen, and other biological materials to a single person.

Quick Review • Two methods used by forensic scientists when examining physical evidence

are identifi cation and comparison. • Identifi cation is the process of determining a substance’s chemical or phys-

ical identity to the exclusion of all other substances (e.g., drugs, explosives, petroleum products, blood, semen, and hair species).

• A comparison analysis determines whether a suspect specimen and a standard/reference specimen have a common origin.

• Evidence that can be linked to a common source with an extremely high degree of probability is said to possess individual characteristics.

• Evidence that is associated with an entire group is said to have class characteristics.

• The overall frequency of occurrence of an event, such as a match between two substances, can be determined by multiplying the frequencies of all independently occurring instances related to that event. This is known as the product rule.

Signifi cance of Physical Evidence One of the current weaknesses of forensic science is the inability of the exam- iner to assign exact or even approximate probability values when comparing most class physical evidence. For example, what is the probability that a nylon fi ber originated from a particular sweater, or that a hair came from a particu- lar person’s head, or that a paint chip came from a car suspected to have been involved in a hit-and-run accident? Very few statistical data are available from which to derive this information, and in a society that is increasingly depen- dent on mass-produced products, the gathering of such data is becoming an increasingly elusive goal.

One of the primary endeavors of forensic scientists must be to create and update statistical databases for evaluating the signifi cance of class physical evidence. Of course, when such information—for example, the population frequency of blood factors—is available, it is used; but, for the most part, the forensic scientist must rely on personal experience when interpreting the signifi cance of class physical evidence.

People who are unfamiliar with the realities of modern criminalistics are often disappointed to learn that most items of physical evidence retrieved at  crime scenes cannot be linked defi nitively to a single person or object ( Figure  4 ). Although investigators always try to uncover physical evidence with individual characteristics—such as fi ngerprints, tool marks, and bullets— the chances of fi nding class physical evidence are far greater. To deny or belittle the value of such evidence is to reject the potential role that criminal- istics can play in a criminal investigation.

In practice, criminal cases are fashioned for the courtroom around a collection of diverse elements, each pointing to the guilt or involvement of a party in the

112

PHYSICAL EVIDENCE

criminal act. Often, most of the evidence gathered is subjective, prone to human error and bias. The believability of eyewitness accounts, confessions, and informant testimony can all be dis- puted, maligned, and subjected to severe attack and skepticism in the courtroom. Under these circumstances, errors in human judgment are often magnifi ed by the defense to detract from the credibility of the witness.

ASSESSING THE VALUE

OF EVIDENCE

The value of class physical evidence hinges on its ability to corroborate events with data in a manner that is, as nearly as possible, free of human error and bias. It is the thread that binds together other investigative fi ndings that are more dependent on human judgments and, therefore, more prone to human failings. The fact that scientists have not yet learned to indi- vidualize many kinds of physical evidence means that criminal investigators should not abdicate or falter in their pursuit of all investigative leads. However, the ability of scientists to achieve a high degree of success in evaluating class physical evidence means that criminal investigators can pursue their work with a much greater chance of success.

Again, defi ning the signifi cance of an item of class evidence in exact mathematical terms is usually a diffi cult if not impos- sible goal. Although class evidence is by its very nature not unique, meaningful items of physical evidence, such as those listed at the beginning of this chapter, are extremely variable in reality. Select, for example, a colored fi ber from an article of clothing and try to locate that exact color on the clothing of random individuals you meet, or select a car color and try to match it to that of other cars you see on local streets. It will be diffi cult to fi nd a match. Furthermore, keep in mind that a forensic comparison goes beyond a mere color comparison and involves examining and comparing a variety of chemical and/or physical properties (see Figure 5 ). The chances are low of encountering two indistinguishable items of physical evidence at a crime scene that actually originated from different sources. Obviously, given these circumstances, only objects that exhibit signifi cant variability are appro- priate for classifi cation as physical evidence.

In the same way, when one is dealing with more than one type of class evi- dence, their collective presence may lead to an extremely high certainty that they originated from the same source. As the number of objects linking an individual to a crime increases, the probability of involvement increases dramatically. A classic example of this situation can be found in the evidence presented at the trial of Wayne Williams. Williams was charged with the murders of two individ- uals in the Atlanta, Georgia, metropolitan area; he was also linked to the mur- ders of ten other boys and young men. An essential element of the state’s case involved the association of Williams with the victims through a variety of fi ber evidence. Actually, twenty-eight types of fi bers linked Williams to the murder victims, evidence that the forensic examiner characterized as “overwhelming.”

CAUTIONS AND LIMITATIONS

IN DEALING WITH PHYSICAL EVIDENCE

In further evaluating the contribution of physical evidence, one cannot overlook one important reality in the courtroom: The weight or signifi cance accorded physical evidence is a determination left entirely to the “trier of fact,” usually a

FIGURE 4 A computer- generated image of DNA superimposed on a fi ngerprint, representing two of the most frequently found individualized items of evidence at crime scenes. Courtesy Alfred Pasieka\Photo Researchers, Inc.

113

PHYSICAL EVIDENCE

jury of laypeople. Given the high esteem in which scientists are generally held by society and the infallible image of forensic science created by books and televi- sion, scientifi cally evaluated evidence often takes on an aura of special reliability and trustworthiness in the courtroom. Often, physical evidence, whether indi- vidual or class, is accorded great weight during jury deliberations and becomes a primary factor in reinforcing or overcoming lingering doubts about guilt or innocence. In fact, a number of jurists have already cautioned against giving carte blanche approval for admitting scientifi c testimony without fi rst considering its relevance to the case. Given the potential weight of scientifi c evidence, failure to take proper safeguards may unfairly prejudice a case against the accused.

Physical evidence may serve also to exclude or exonerate a person from suspicion. For instance, if type A blood is linked to the suspect, all individu- als who have types B, AB, and O blood can be eliminated from consideration. Because it is not possible to assess at the crime scene what value, if any, the scientist will fi nd in the evidence collected or what signifi cance such fi ndings will ultimately have to a jury, the thorough collection and scientifi c evaluation of physical evidence must become a routine part of all criminal investigations.

Just when an item of physical evidence crosses the line that distinguishes class from individual is diffi cult to determine and is often the source of heated debate and honest disagreement among forensic scientists. How many striations are necessary to individualize a mark to a single tool and no other? How many color layers individualize a paint chip to a single car? How many ridge characteristics individualize a fi ngerprint, and how many handwriting characteristics tie a per- son to a signature? These questions defy simple answers. The task of the forensic scientist is to fi nd as many characteristics as possible to compare one substance with another. The signifi cance attached to the fi ndings is decided by the quality and composition of the evidence, the case history, and the examiner’s experience. Ultimately, the conclusion can range from mere speculation to near certainty.

FIGURE 5 A side-by-side comparison of fi bers. Courtesy Chris Palenik, Microtrace LLC, Elgin, IL, www.microtracescientifi c.com

114

PHYSICAL EVIDENCE

There are practical limits to the properties and characteristics the forensic scientist can select for comparison. Carried to the extreme, no two things in this world are alike in every detail. Modern analytical techniques have become so sophisticated and sensitive that the criminalist must defi ne the limits of natural variation among materials when interpreting the data gathered from a comparative analysis. For example, two properties, density and refractive index, are best suited for comparing two pieces of glass. But the latest tech- niques that have been developed to measure these properties are so sensitive that they can even distinguish glass originating from a single pane of glass. Certainly this goes beyond the desires of a criminalist trying to determine only whether two glass particles originated from the same window. Similarly, if the surface of a paint chip is magnifi ed 1,600 times with a powerful scanning electron microscope, fi ne details are revealed that could not be duplicated in any other paint chip from the very same painted surface. Under these circum- stances, no two paint chips, even those coming from the same surface, could ever compare in the truest sense of the word. Therefore, practicality dictates that such examinations be conducted at a less revealing, but more meaningful, magnifi cation (see Figure 6 ).

Distinguishing evidential variations from natural variations is not always an easy task. Learning how to use the microscope and all the other modern instruments in a crime laboratory properly is one thing; gaining the profi ciency needed to interpret the observations and data is another. As new crime laboratories are created and others expand to meet the requirements of the law enforcement community, many individuals are starting new careers in forensic science. They must be cautioned that merely reading relevant textbooks and journals is no substitute for experience in this most practical of sciences.

Quick Review • The value of class physical evidence lies in its ability to corroborate events

with data in a manner that is, as nearly as possible, free of human error and bias.

• As the number of objects linking an individual to a crime scene increases, so does the likelihood of that individual’s involvement with the crime.

• A person may be exonerated or excluded from suspicion if physical evidence collected at a crime scene is found to be different from standard/ reference samples collected from that subject.

Forensic Databases In a criminal investigation, the ultimate contribution a criminalist can make is to link a suspect to a crime through comparative analysis. This comparison defi nes the unique role of the criminalist in a criminal investigation. Of course, a one-on-one comparison requires a suspect. Little or nothing of evidential value can be accomplished if crime-scene investigators acquire fi ngerprints, hairs, fi bers, paint, blood, and semen without the ability to link these items to a suspect. In this respect, computer technology has dramatically altered the role of the crime laboratory in the investigative process.

No longer is the crime laboratory a passive bystander waiting for inves- tigators to uncover clues about who may have committed a crime. Today, the crime laboratory is on the forefront of the investigation seeking to identify perpetrators. This dramatic enhancement of the role of forensic science in criminal investigation has come about with the creation of computerized data- bases that not only link data from all fi fty states but also tie together data from police agencies throughout the world.

115

PHYSICAL EVIDENCE

FINGERPRINT DATABASES

The premier model of all forensic database systems is the Integrated Automated Fingerprint Identifi cation System (IAFIS), a national fi ngerprint and criminal history system maintained by the FBI and launched in 1999. IAFIS contains the fi ngerprints and corresponding criminal history information of nearly 68  million subjects (i.e., 680 million fi ngerprint images), which are submitted voluntarily to the FBI by state, local, and federal law enforcement agencies.

FIGURE 6 (a) A two-layer paint chip magnifi ed 244 times with a scanning electron microscope. (b) The same paint chip viewed at a magnifi cation of 1,600 times.

(a)

(b)

116

PHYSICAL EVIDENCE

A crime-scene fi ngerprint or latent fi ngerprint is a dramatic fi nd for the criminal investigator. Once the quality of the print has been deemed suitable for the IAFIS search, the latent-print examiner creates a digital image of the print with either a digital camera or a scanner. Next, the examiner, with the aid of a coder, marks points on the print to guide the computerized search (see Figure  7 ). The print is then electronically submitted to IAFIS, and within minutes the search of all fi ngerprint images in IAFIS is com- pleted; the examiner may receive a list of potential candidates and their corresponding fi ngerprints for comparison and verifi cation (see Figure 8 ).

Many countries throughout the world have created national automated fi ngerprint identifi cation systems that are comparable to the FBI’s model. For example, a computerized fi ngerprint database containing nearly nine million ten-print records connects the Home Offi ce and forty-three police forces throughout England and Wales.

DNA DATABASES

In 1998, the FBI’s Combined DNA Index System (CODIS) became fully operational. CODIS enables federal, state, and local crime laboratories to electronically exchange and compare DNA profi les, thereby linking crimes to each other and to convicted offenders. All fi fty states have enacted legislation to establish a data bank containing DNA profi les of individuals convicted of felony sexual offenses (and other crimes, according to each state’s statute).

CODIS creates investigative leads from two sources: the forensic index and the offender index. The forensic index currently contains about 380,000 profi les recovered from crime-scene evidence without a suspect. Based on a match, police in multiple jurisdictions can identify serial crimes, allowing

FIGURE 7 A forensic scientist using the AFIS database. Mikael Karlsson\Arresting Images

FIGURE 8 The computerized search of a fi ngerprint database fi rst requires that selected ridge characteristics be designated by a coder. The positions of these ridge characteristics serve as a basis for comparing the print against fi ngerprints on fi le. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

117

PHYSICAL EVIDENCE

coordination of investigations and sharing of leads developed indepen- dently. The offender index contains the profi les of nearly 10.5 million con- victed or arrested individuals. The FBI has joined fi fteen states that collect DNA from those awaiting trial and from detained immigrants. This informa- tion will be entered into an arrestee index database. Unfortunately, hundreds of thousands of samples are backlogged, still awaiting DNA analysis and entry into CODIS. Law enforcement agencies search this index against DNA profi les recovered from biological evidence found at unsolved crime scenes. This approach has been tremendously successful in identifying perpetrators because most crimes involving biological evidence are committed by repeat offenders.

Several countries throughout the world have initiated national DNA data banks. The United Kingdom’s National DNA Database , established in 1995, was the world’s fi rst national database. Currently it holds more than four million profi les, and DNA samples can be taken for entry into the database from any- one arrested for an offense likely to involve a prison term. In a typical month, DNA matches link individuals in the database to 26 murders; 57 rapes and other sexual offenses; and 3,000 motor vehicle, property, and drug crimes.

OTHER DATABASES

The National Integrated Ballistics Information Network (NIBIN) maintained by the Bureau of Alcohol, Tobacco, Firearms and Explosives, allows fi rearms an- alysts to acquire, digitize, and compare markings made by fi rearms on bullets and cartridge casings recovered from crime scenes. The NIBIN program cur- rently has 236 sites that are electronically joined to sixteen multistate regions.

The heart of NIBIN is the Integrated Ballistic Identifi cation System (IBIS), comprising a microscope and a computer unit that can capture an image of a bullet or cartridge casing. The images are then forwarded to a regional server, where they are stored and correlated to other images in the regional database. IBIS does not positively match bullets or casings fi red from the same weapon;

CASEFILES In 1975, police found Gerald Wallace’s body on his living room couch. He had been savagely beaten, his hands bound with an electric cord. Detectives searched his ransacked house, cataloging every piece of evidence they could fi nd. None of it led to the murderer. They had no witnesses. Sixteen years after the fact, a lone fi ngerprint, lifted from a cigarette pack found in Wallace’s house and kept for sixteen years

in the police fi les, was entered into the Pennsylvania State Police AFIS database. Within minutes, it hit on a match. That print, police say, gave investigators the identity of a man who had been at the house the night of the murder. Police talked to him. He led them to other witnesses, who led police to the man who was ultimately charged with the murder of Gerald Wallace.

CASEFILES Fort Collins, Colorado, and Philadelphia, Pennsylvania, are separated by nearly 1,800 miles, but in 2001 they were tragically linked though DNA. Troy Graves left the Philadelphia area in 1999, joined the air force, and settled down with his wife in Colorado. Subsequently, a frenzied string of eight sexual assaults around the Colorado University campus set off a manhunt that ultimately resulted in the arrest of Graves. However, his DNA profi le inextricably identifi ed

him as Philadelphia’s notorious “Center City rapist.” This assailant had attacked four women in 1997 and brutally murdered Shannon Schieber, a Wharton School graduate student, in 1998. His last known attack in Philadelphia was the rape of an 18-year-old student in August 1999, shortly before Graves left the city. In 2002, Graves was returned to Philadelphia, where he was sentenced to life in prison without parole.

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this must be done by a fi rearms examiner. IBIS does, however, facilitate the work of the fi rearms examiner by producing a short list of candidates for the examiner to manually compare. Nearly 1.6 million pieces of crime-scene evi- dence have been entered in NIBIN, and more than 34,000 “hits” have been recorded, many of them yielding investigative information not obtainable by other means.

The International Forensic Automotive Paint Data Query (PDQ) database contains chemical and color information pertaining to original automotive paints. This database, developed and maintained by the Forensic Laboratory Services of the Royal Canadian Mounted Police (RCMP), contains informa- tion about the make, model, year, and assembly plant of more than 13,000 vehicles, with a library of more than 50,000 layers of paint. Contributors to the PDQ include the RCMP and forensic laboratories in Ontario and Quebec, as well as forty US forensic laboratories and police agencies in twenty-one other countries. Accredited users of PDQ are required to submit sixty new automo- tive paint samples per year to be added to the database. The PDQ database has found its greatest utility in the investigation of hit-and-runs by providing police with possible make, model, and year information to aid in the search for the unknown vehicle.

CASEFILES A 53-year-old man was walking his dog in the early morning hours. He was struck and killed by an unknown vehicle and later found lying in the roadway. No witnesses were present, and the police had no leads regarding the suspect vehicle. A metallic-gold-painted plastic fragment recovered from the scene and the victim’s clothing were submitted to the Virginia Department of Forensic Science for analysis.

The victim’s clothing was scraped, and several minute, metallic gold paint particles were recovered. The majority of these particles contained only topcoats, but one very minute particle contained two primer layers and a very limited amount of topcoat. The color of the primer surfacer layer was similar to that typically associated with some Fords. Subsequent spectral searches in the PDQ database indicated that the paint probably originated from a 1990 or newer Ford.

The most discriminating aspect of this paint was the unusual- looking metallic gold topcoat. A search of automotive repaint books yielded only one color that closely matched the paint recovered in

this case. The color, Aztec Gold Metallic, was determined to have been used only on 1997 Ford Mustangs.

The results of the examination were relayed via telephone to the investigating detective. The investigating detective quickly determined that only 11,000 1997 Ford Mustangs were produced in Aztec Gold Metallic. Only two of these vehicles were registered and had been previously stopped in the jurisdiction of the offense. Ninety minutes after the make/model/year information was relayed to the investigator, he called back to say he had located a suspect vehicle. Molding from the vehicle and known paint samples were submitted for comparison. Subsequent laboratory comparisons showed that the painted plastic piece recovered from the scene physically fi tted together with the molding on the car, and the paint recovered from the victim’s clothing was consistent with paint samples taken from the suspect vehicle.

Source: Brenda Christy, Virginia Department of Forensic Science. Reprinted by permission.

CASEFILES After a series of armed robberies in which suspects fi red shots, the sheriff’s offi ce of Broward County, Florida, entered the cartridge casings from the crime scenes into NIBIN. Through NIBIN, four of the armed robberies were linked to the same .40-caliber handgun. A  short time later, sheriff’s deputies noticed suspicious activity around a local business. When they attempted to interview the suspects, the suspects fl ed in a vehicle. During the chase, the

suspects attempted to dispose of a handgun; deputies recovered the gun after making the arrests. The gun was test-fi red, and the resulting evidence was entered into NIBIN, which indicated a possi- ble link between this handgun and the four previous armed robber- ies. Firearms examiners confi rmed the link by examining the original evidence. The suspects were arrested and charged with four prior armed robbery offenses.

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The previously described databases are maintained and controlled by government agencies. There is one exception: a commercially available computer retrieval system for comparing and identifying crime-scene shoe prints known as SICAR (Shoeprint Image Capture and Retrieval) . 1 SICAR’s pattern-coding system enables an analyst to create a simple description of a shoe print by assigning codes to individual pattern features (see Figure 9 ). Shoe print images can be entered into SICAR via either a scanner or a digital camera. This product has a comprehensive shoe sole database (SoleMate ® ) that includes more than 22,000 footwear entries providing investigators with a means for linking a crime-scene footwear impression to a particular shoe manufacturer. A second database, TreadMate ® , has been created to house tire tread patterns. Currently, it contains 6,000 records.

Quick Review • The creation of computerized databases for fi ngerprints, criminal histories,

DNA profi les, markings on bullets and cartridges, automotive paints, and shoe prints has dramatically enhanced the role of forensic science in criminal investigation.

• IAFIS is the Integrated Automated Fingerprint Identifi cation System, a national fi ngerprint and criminal history database maintained by the FBI. IAFIS allows criminal investigators to compare fi ngerprints at a crime scene to an index of 680 million known prints. CODIS is the FBI’s Combined DNA Index System. It enables federal, state, and local crime laboratories to electronically exchange and compare DNA profi les, linking crimes to each other and to convicted offenders.

FIGURE 9 The crime-scene footwear print on the right is being searched against eight thousand sole patterns to determine its brand and style. Courtesy Foster & Freeman Limited, Worcestershire, UK, www.fosterfreeman.co.uk

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PHYSICAL EVIDENCE

Forensic Palynology: Pollen and Spores as Evidence Of the many plant species on earth, more than half a million produce pollen or spores. The pollen or spores produced by each species has a unique type of ornamentation and morphology. This means that pollen or spores can be identifi ed and used to provide links between a crime scene and a person or object if examined by a trained analyst. This technique is called forensic palynology and includes the collection and examination of pollen and spores connected with crime scenes, illegal activities, or terrorism. Microscopy is the principal tool used in the fi eld of forensic palynology.

CHARACTERISTICS

OF SPORES AND POLLEN

In nature, pollen grains are the single-celled male gametophytes (reproductive cells) of seed-bearing plants. The pollen grain wall ( exine ) is durable because it protects and carries the “sperms” needed for plant reproduction. Spores consist of both the male and female gametes of plants such as algae, fungi, mosses, and ferns. Pollen-producing plants are either anemophilous (their pollen is dispersed by wind) or entomophilous (their pollen is carried and dispersed by insects or small animals). Fairly precise geographical locations can often be identifi ed by the presence of different mixtures of airborne pollens pro- duced by anemophilous plants. For example, it may be possible to identify a geographical origin using a profi le of the pollen samples retrieved from a suspect’s cloth- ing by analyzing the type and percentages of airborne pollen grains. Entomophilous plants usually produce a small amount of pollen that is very sticky in nature. Therefore, this type of pollen is very rarely deposited on clothing or other objects except by direct contact with the plant. This information is useful when reconstruct- ing the events of a crime because it may indicate that the clothing, a vehicle, or other objects on which this pollen is found came into direct contact with plant types found at a crime scene.

ANALYSIS OF SPORES

AND POLLEN

Both spores and pollen are microscopic in size and are produced by adult plants, then dispersed by the millions, and both can be analyzed using similar methods that use a variety of microscopic techniques. Using a compound light microscope with magnifi cation capabilities up to 1,000�, analysts usually can identify pollen and spores as having come from a specifi c plant family or genus, and sometime even the unique species. However, often the pollen or spores of related species may look so similar that identifi cation of the species is possible only by careful analysis using a scanning elec- tron microscope (SEM) (see Figure 10 ).

Unique shapes, aperture type, and surface ornamentation are typically used to identify spore

FIGURE 10 Allergenic pollen grains of ragweed. Common ragweed (Ambrosia artemisiifolia) is the most widespread of this genus in North America. Each ragweed plant is able to produce up to a billion grains of pollen over a season, and the plant is anemophilous (wind- pollinated). It is highly allergenic, has the greatest pollen allergen of all pollens, and is the prime cause of hayfever. The plant blooms in the northern hemisphere from about mid-August until cooler weather arrives. It usually produces pollen more copiously in wet seasons. Two species, Ambrosia artemisiifolia and A. psilostachya, are considered among the most noxious to those prone to hay fever. The ragweed was accidentally imported to Europe during World War I; it has adapted to the different environment successfully and has spread widely since the 1950s. Hungary is currently the most heavily affected country in Europe (and possibly the entire world), especially since the early 1990s, when abandonment of communist-style collective agriculture left vast fi elds uncultivated and those fi elds were promptly invaded by ragweed. Enhanced SEM. Magnifi cation: 1170X if the image is printed 10cm wide. © Medical-on-Line / Alamy

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samples. Useful features for characterizing pollen grains include shape, aper- tures, and wall and surface sculpturing. Shapes of pollen grains include spheres, triangles, ellipses, hexagons, pentagons, and many other geometric variations. Apertures are the openings on pollen grains from which the pollen tube grows and carries the sperms to the egg to complete fertilization. Sculpturing of the pollen refers to the pattern of the pollen grain surface.

To avoid destruction or contamination of pollen evidence, early collection of forensic pollen samples for analysis is important and should be completed as soon as possible at a crime scene by a trained palynologist. This expert’s fi rst task is to calculate the estimated production and dispersal patterns of spores and pollen (called the pollen rain ) for the crime scene or area of interest and, using that information, to produce a kind of “pollen fi ngerprint” of that location.

The information gained from the analysis of pollen and spore evidence has many possible uses. It can link a suspect or object to the crime scene or the victim, prove or disprove a suspect’s alibi, include or exclude suspects, track the previous whereabouts of some item or suspect, or indicate the geographical origin of some item. In the past, pollen and spore evidence has been used to locate human remains and concealed burial sites, establish the season or time of death of a victim, locate the source areas of illegal drugs and fake pharmaceuticals, identify terrorists, and prove the perpetration of illegal poaching and the adulteration of commercial foods.

A case exemplifying the application of forensic palynology to a criminal in- vestigation occurred when a victim was kidnapped, robbed, and then murdered in the eastern part of the American Midwest. 2 The victim’s car was stolen but later abandoned when it got stuck in mud near a busy highway. The next night a drifter was arrested in a nearby town for breaking into a closed store. While in jail awaiting trial, the drifter told a fellow inmate about his car being stuck in the mud, stating that he would not be in jail but for that mishap. The other pris- oner, hoping to work a deal for a lighter sentence, told this story to the sheriff.

During the investigation of the crime scene, one of the law enforcement agents noticed that there was a large fi eld of mature corn growing between the dirt road where the stolen car had been abandoned in the mud and the nearby highway leading to the next town. The investigator wondered if traces of torn corn leaves on the suspect’s clothing might link him to the crime scene. Fortunately, the drifter’s shirt and pants had been removed and stored in ster- ile paper bags when he was arrested. As were all prisoners in that region, he had been given a pair of orange overalls to wear while in jail.

The shirt and pants were sent to a botanist, who was asked to search for traces of corn leaves on the clothing. The botanist was also a palynologist, and thus also collected samples and searched for traces of pollen. The pollen samples yielded the best results. The samples collected from the suspect’s shirt revealed that the neck and shoulder region of the shirt had high concentrations of fresh corn pol- len. The forensic sample collected from the pants also contained corn pollen but in lower numbers. The forensic pollen data indicated that the drifter had recently walked through a corn fi eld similar to the one between the abandoned car and the highway. As he walked through the fi eld, he had brushed against the bloom- ing male tassels on the corn plants, which are about head high. This accounted for the large amount of corn pollen found on the shoulder and neck area of the shirt. Lesser amounts of corn pollen also fell on the drifter’s pants as he walked through the fi eld. While the suspect awaited trial, additional evidence and several fi ngerprints from the victim’s farm also linked him to the murder.

Quick Review • Forensic palynology involves the collection and examination of pollen and

spores connected with crime scenes, illegal activities, or terrorism. The microscope is the principal tool used in the fi eld of forensic palynology.

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PHYSICAL EVIDENCE

• The information gained from the analysis of pollen and spore evidence has many possible uses. It can link a suspect or object to the crime scene or the victim, prove or disprove a suspect’s alibi, include or exclude suspects, track the previous whereabouts of some item or suspect, or indicate the geographical origin of some item.

CHAPTER REVIEW

REVIEW QUESTIONS

• Two methods used by forensic scientists when examining physical evidence are identifi cation and comparison.

• Identifi cation is the process of determining a substance’s chemical or physical identity to the exclusion of all other substances (e.g., drugs, explosives, petroleum products, blood, semen, and hair species).

• A comparison analysis determines whether a suspect specimen and a standard/reference specimen have a common origin.

• Evidence that can be associated with a common source with an extremely high degree of probability is said to possess individual characteristics.

• Evidence associated with only a group is said to have class characteristics.

• The overall frequency of occurrence of an event, such as a match between two substances, can be obtained by multiplying the frequencies of all independently occurring instances related to that event. This is known as the product rule.

• The value of class physical evidence lies in its ability to corroborate events with data in a manner that is, as nearly as possible, free of human error and bias.

• As the number of objects linking an individual to a crime scene increases, so does the likelihood of that individual’s involvement with the crime.

• A person may be exonerated or excluded from suspicion if phys- ical evidence collected at a crime scene is found to be different from standard/reference samples collected from that subject.

• The creation of computerized databases for fi ngerprints, crimi- nal histories, DNA profi les, markings on bullets and cartridges, automotive paints, and shoe prints has dramatically enhanced the role of forensic science in criminal investigation.

• IAFIS is the Integrated Automated Fingerprint Identifi cation System, a national fi ngerprint and criminal history database maintained by the FBI. IAFIS allows criminal investigators to compare fi ngerprints at a crime scene to an index of 680  million known prints. CODIS is the FBI’s Combined DNA Index System. It enables federal, state, and local crime laboratories to electronically exchange and compare DNA pro- fi les, linking crimes to each other and to convicted offenders.

• Forensic palynology involves the collection and examination of pollen and spores connected with crime scenes, illegal activities, or terrorism. The microscope is the principal tool used in the fi eld of forensic palynology.

1. The process of ______________ determines a substance’s physical or chemical identity with the most certainty that existing analytical techniques will permit.

2. The number and type of tests needed to identify a substance must be suffi cient to ______________ all other substances from consideration.

3. A(n) ______________ analysis subjects a suspect and a stan- dard/reference specimen to the same tests and examination for the ultimate purpose of determining whether they have a common origin.

4. ______________ is the frequency of occurrence of an event.

5. Evidence that can be traced to a common source with an extremely high degree of probability is said to possess ______________ characteristics.

6. Evidence associated with a group, not a single source, is said to possess ______________ characteristics.

7. True or False: One of the major defi ciencies of forensic sci- ence is the inability of the examiner to assign exact or ap- proximate probability values to the comparison of most class physical evidence. ______________

KEY TERMS

class characteristics

comparison

identifi cation

individual characteristics

product rule

123

APPLICATION AND CRITICAL THINKING

ENDNOTES

1. Arrange the following tasks in order, from the one that would require the least extensive testing procedure to the one that would require the most extensive. Explain your answer.

a) Determining whether an unknown substance contains an illicit drug

b) Determining the composition of an unknown substance

c) Determining whether an unknown substance contains heroin

2. The following are three possible combinations of DNA char- acteristics that might be found in an individual’s genetic profi le. Using the probability rule, rank each of these combi- nations from most common to least common. The number in parentheses after each characteristic indicates its percentage distribution in the population.

a) FGA 24,24 (3.6%), TH01 6,8 (8.1%), and D16S539 11, 12 (8.9%)

b) vWA 14,19 (6.2%), D21S11 30,30 (3.9%), and D13S317 12,12 (8.5%)

c) CSF1PO 9,10 (11.2%), D18S51 14,17 (2.8%), and D8S1179 17,18 (6.7%)

3. For each of the following pieces of evidence, indicate whether the item is more likely to possess class or individual charac- teristics. Explain your answers.

a) An impression from a new automobile tire

b) A fi ngerprint

c) A spent bullet cartridge

d) A mass-produced synthetic fi ber

e) Pieces of a shredded document

f) Commercial potting soil

g) Skin and hair scrapings

h) Fragments of a multilayer custom automobile paint

4. Which of the forensic databases described in the text con- tain information that relates primarily to evidence exhibiting class characteristics? Which ones contain information that relates primarily to evidence exhibiting individual character- istics? Explain your answers.

5. An investigator at a murder scene notes signs of a prolonged struggle between the attacker and victim. Name at least three types of physical evidence for which the investigator would probably collect standard/reference samples, and explain why he or she would collect them.

1. Foster & Freeman Limited, Worcestershire, UK, www.fosterfreeman.co.uk .

2. V. M. Bryant and G. D. Jones, “Forensic Palynology: Current Status of a Rarely Used Technique in the United States of

America,” Forensic Science International 163 (2006): 183–197.

8. Although databases are consistently updated so that scien- tists can assign probabilities to class evidence, for the most part, forensic scientists must rely on ______________ when interpreting the signifi cance of class physical evidence.

9. The believability of ______________ accounts, confessions, and informant testimony can all be disputed, maligned, and subjected to severe attack and skepticism in the courtroom.

10. The value of class physical evidence lies in its ability to ______________ events with data in a manner that is, as nearly as possible, free of human error and bias.

11. The ______________ accorded physical evidence during a trial is left entirely to the trier of fact.

12. True or False: Given the potential weight of scientifi c evidence in a trial setting, failure to take proper safeguards may un- fairly prejudice a case against the suspect. ______________

13. True or False: Physical evidence cannot be used to exclude or exonerate a person from suspicion of committing a crime. ______________

14. True or False: The distinction between individual and class evidence is always easy to make. ______________

15. Modern analytical techniques have become so sensi- tive that the forensic examiner must be aware of the ______________ among materials when interpreting the signifi cance of comparative data.

16. Students studying forensic science must be cautioned that merely reading relevant textbooks and journals is no substi- tute for ______________ in this most practical of sciences.

17. True or False: A fi ngerprint can be positively identifi ed through the IAFIS database. ______________

18. A database applicable to DNA profi ling is the FBI’s ______________ .

19. True or False: Both spores and pollen can be identifi ed and used to link a crime scene to an individual. ______________

20. True or False: Spores can be characterized by shape and sur- face characteristics through a simple visual examination. ______________

PHYSICAL EVIDENCE

124

HAROLD SHIPMAN, DR. DEATH Kathleen Grundy’s sudden death in 1998 was shocking news to her daughter, Angela Woodruff. Mrs. Grundy, an 81-year-old widow, was believed to be in good health when her physician, Dr. Harold Shipman, visited her a few hours before her demise. Some hours later, when friends came to her home to check on her whereabouts, they

found Mrs. Grundy lying on a sofa fully dressed and dead.

Dr. Shipman pronounced her dead and informed her daughter that an autopsy was not necessary. A few days later, Mrs. Wood- ruff was surprised to learn that a will had surfaced leaving all of Mrs. Grundy’s money to Dr. Shipman. The will was immediately recognized as a forgery and led to the exhumation of Mrs. Grundy’s body. A toxi- cological analysis of the remains revealed a lethal quantity of morphine.

In retrospect, there was good reason to suspect that Dr. Shipman was capable of foul play. In the 1970s, he was asked to leave a medical practice because of a drug abuse problem and charges that he obtained drugs by forgery and deception. However, Dr. Shipman was quickly back to practicing medicine. By 1998, local under-

takers became suspicious because of the number of his patients who were dying. What is more, the patients that had died all were elderly women who were found sitting in a chair or lying fully clothed on a bed. As police inves- tigated, the horror of Dr. Shipman’s deeds became appar- ent. One clinical audit estimated that Dr. Shipman had killed at least 236 of his patients over a twenty-four-year period. Most of the deaths were attributed to fatal doses of heroin or morphine. Toxicological analysis on seven exhumed bodies clearly showed signifi cant quantities of morphine. Convicted of murder, Dr. Shipman hanged him- self in his jail cell in 2004.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Describe the role of the forensic pathologist • Distinguish cause and manner of death • Describe common causes of death • Describe the external, internal, and toxicology phases of an

autopsy • List various categories associated with the manner of death • Describe chemical and physical changes helpful for estimating

time of death • Discuss the role of the forensic anthropologist in death

investigation • Describe the role of the forensic entomologist in death

investigation

Death

Investigation

Phil Noble/AFP/Newscom

From Chapter 6 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

DEATH INVESTIGATION

Role of the Forensic Pathologist Few investigations bring with them the intense focus of community interest and news media coverage as that of a suspicious death. Generally, forensic pathologists associated with the medical examiners’ or coroner’s offi ce are responsible for determining the cause of an undetermined or unexpected death. These offi cers will coordinate their response with that of law enforce- ment in the ensuing investigation. The titles coroner and medical examiner are often used interchangeably, but there are signifi cant differences in their job descriptions. In the United States, there’s a mix of state medical examiner systems, county medical examiner offi ces, and county coroner systems. The coroner is an elected offi cial and may or may not possess a medical degree. (The term coroner dates back hundreds of years to the rule of King Henry II of England, who created the offi ce of the coroner to collect money and personal possessions from people who had died.) The medical examiner, on the other hand, is almost always an appointed offi cial and is usually a physician who generally is a board-certifi ed forensic pathologist and is responsible for certi- fying the manner and the cause of a death.

The tasks of examining the death for the cause and manner of death and recording the results in a death certifi cate are the responsibilities of both offi ces. However, although both the coroner’s offi ce and the medical examiner’s offi ce are charged with investigating suspicious deaths, only the pathologist is trained to perform an autopsy. Ideally, the coroner or medical examiner’s offi ce should be staffed with physicians who are board certifi ed in forensic pathology and should charge them with determining the cause of death by autopsy. The cause-of-death determination, however, involves not just an autopsy but also the history of death, witness statements, relevant medical records, and any scene investigation, all of which constitute the surrounding circumstances of death.

From a practical point of view, it is often not feasible for the forensic pathologist to personally solicit information regarding the circumstances surrounding a death or to respond in-person to every death scene. Thus, the gathering of vital information and the scene investigation can be delegated to trained coroner/medical examiner investigators who, when a crime scene is involved, coordinate their efforts with the those of crime-scene and crimi- nal investigators. The forensic pathologist’s work is also aided by the skills of specialists including forensic anthropologists, forensic entomologists, and forensic odontologists.

SCENE INVESTIGATION

With regard to any scene investigation, protection of the overall scene and the body are of paramount importance, as is the ultimate removal of the body in a medically acceptable manner. The death investigation involves document- ing and photographing the undisturbed scene; collecting relevant physical evidence; attempting to determine time of death, which must be done in a timely fashion at the scene; and, among other things, ascertaining premortem locations of the body and whether any postmortem movement of the body occurred. Examples of observations that can be made of the body at the scene include bruises along the upper lip, which may be evidence of smothering; a black eye limited to the eyelids, which implies an injury from inside the head; or bleeding from the ear, which implies a basal skull fracture.

A critical phase of the death investigation will be a preliminary recon- struction of events that preceded the onset of death, so all signifi cant details of the scene must be recorded. Blood spatter and blood fl ow patterns must be

forensic pathologists Investigative personnel, typically medical examiners or coroners, who investigate the cause, manner and time of death of a victim in a crime. A physician who has been trained to conduct autopsies.

126

DEATH INVESTIGATION

documented. Blood should be sampled for testing in case some of the blood was cast off by a perpetrator. Any tire marks or shoe prints must be documented. Fingerprints must be processed and collected. Of particular importance is the search for any evidence discarded, dropped, or cast off by a perpetrator. When a weapon is involved, there must be a concerted effort to locate and recover the suspect weapon. In the case of fi rearm deaths, fi red bullets or casings must be found and their locations documented. In such fi rearm deaths, before the body is moved or clothing is removed, blood spatter directionality and trace evidence (such as hairs) on the hands must be documented. Paper bags then should be placed over the hands and secured around the wrist or arm (paper prevents moisture condensation) to preserve any additional evidence.

Photographs must always be taken before the scene is altered in any way (except from life-saving efforts). This includes moving the body or anything on the body, such as clothing or jewelry. A particularly violent scene can carry with it a large amount of blood and disorder. Blood may be found at different locations throughout the scene. This could prove to be important in shaping the events that led to the fi nal outcome; it may be possible to determine  the initial location of the injury, as well as victim and assailant movements throughout the course of events. Initially it may be diffi cult to properly infer the source of the wounds and the order in which they were received at the scene. Photographs then will play a very large role when reconstructing the events later. As always, photographs should be taken with a scale, always fi rst overall, then at medium range, then close up. The photographer must also be careful not to get caught up in capturing the injuries exclusively. Negative fi ndings can also be signifi cant. This means photographs should also be taken of areas on the body where injuries are not apparent.

Protection of the body and the overall scene is of paramount importance, as is the ultimate removal of the body in a medically acceptable manner. Often the initial phase of the investigation will focus on determining the identity of the deceased, often called the decedent . Although this task may be relatively simple to accomplish through a visual examination, complications can arise. Body decomposition and the existence of extensive trauma can complicate the identifi cation. This may necessitate the application of more sophisticated technology, such as DNA, fi ngerprinting, dental examination, and facial reconstruction.

Quick Review • Forensic pathologists associated with the medical examiners’ or coroner’s

offi ce are responsible for determining the cause of an undetermined or unexpected death.

• Although both the coroner’s offi ce and the medical examiner’s offi ce are charged with investigating suspicious deaths, only the pathologist is trained to perform an autopsy. The tasks of examining a body for the cause and manner of death and recording the results in the death certifi cate are the responsibilities of both offi ces.

• Protection of the body and the overall scene is of paramount importance, as is the ultimate removal of the body in a medically acceptable manner.

CAUSE OF DEATH

A primary objective of the autopsy is to determine the cause of death. The cause of death is that which initiates the series of events ending in death. The most im- portant determination in a violent death is the character of the injury that started the chain of events that resulted in death. However, if the sequence of events leading to death is suffi ciently prolonged, then the decedent may actually suffer

cause of death Identifi es the injury or disease that led to the chain of events resulting in death.

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DEATH INVESTIGATION

from adverse medical conditions brought about by the initial injury and then die as a result of those conditions. In that case, it will be up to the forensic pathologist to make the determination that the origi- nal injury infl icted on the victim was the underlying cause of death. Some of the more common causes of death are discussed here.

BLUNT FORCE INJURY A blunt force injury is caused a non- sharpened object such a bat or pipe. A blunt force injury can abrade, or scrape, tissue. If tissue is crushed by a blunt force to the point of tearing, an open wound, called a laceration, is produced. Lacerations exhibit abrasions around the open wound, tissue bridg- ing within the open wound, and torn or disturbed tissue beneath the skin surrounding the open portion of the wound. Blunt force injury can also crush tissue. This will cause bleeding from tiny ruptured blood vessels within and beneath the skin, known as a contusion, or bruise (see Figure 1 ). Much has been written about determining the age of bruises, but forensic pathologists have become keenly aware that attempting to “age” bruises based on color and changes in color over time is fraught with diffi culty, and contusions must be interpreted with great care and reserve. Some contusions only become visible externally over time, and frequently, bruises will not be visible externally but become eminently visible internally within soft tissues (e.g., in the abdomen, and on the back, arms, and legs).

A contusion can sometimes exhibit the pattern of the weapon used. For example, if a person wearing a ring strikes another person, the ring may imprint its pattern onto the skin. A person who stomps on another may leave the impression of his or her shoe heel. Over time, however, the bruise will lose its original shape and pattern and undergo color changes. Some objects will produce a characteristic bruised perimeter and a white center.

The outward appearance of the injuries does not always coincide with the injuries sustained inside the body. This is something the pathologist must keep in mind when examining blunt force injuries. A single blow to certain parts of the body can cause instantaneous death with little visible damage. Likewise, a blow to the head can cause a concussion that can be instantly fatal.

SHARP FORCE INJURIES Sharp force injuries occur from weapons with sharp edges, such as knives or blades. These weapons are capable of cutting or stabbing. A cut is formed when the weapon produces an injury that is longer than it is deep. In contrast, a stab is deeper than its length. As shown in Figure  2 , the tissue associated with these types of wounds is not crushed or torn but sliced.

A scene that involves a sharp force injury is usually especially bloody and unruly. Blood may be found at different locations throughout the scene. Again, this information may make it possible to determine the initial location of the injury as well as where the body was moved throughout the course of events. Particularly important in sharp force cases is to examine the victim for defensive wounds. A victim’s forearm that exhibits wounds may indicate defense wounds. These occur when the victim attempts to fi ght off the attacker or block assaults. Though defense wounds are more typical on the outer forearms, they can also be evident on the lower extremities if the victim tries to protect him- or herself by kicking. A lack of any defense wounds can lead a pathologist to conclude that the victim was either unconscious or somehow tied up during the assault.

ASPHYXIA Asphyxia encompasses a variety of conditions that involve interference with the intake of oxygen. For example, death at a fi re scene is caused primarily by the extremely toxic gas, carbon monoxide. When carbon

FIGURE 1 Bruising (contusions) on the skin. Courtesy Rockland County, NY, Medical Examiner’s Offi ce. © All rights reserved.

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monoxide is present, hemoglobin, the protein in red blood cells that transports oxygen, will bind to the carbon monoxide in- stead of oxygen. This is carbon monoxide poisoning, and this deadly complex of hemoglobin and carbon monoxide is known as carboxyhemoglobin. Bound up with carbon monoxide, the hemoglobin is prevented from transporting oxygen throughout the body, causing asphyxia. High levels of carbon monoxide in the blood will cause death. Low levels of carbon monoxide can cause a victim to become disoriented and lose consciousness.

Carbon monoxide will not continue to build up in the body after death. The levels found in a fi re victim then can be used to determine whether the individual was breathing at the time of the fi re. The pres- ence of soot is another indicator that the victim was alive during the fi re. These black particles are often seen in the airway of fi re victims that inhaled smoke before death. During the autopsy, soot can be observed especially in the larynx and trachea and even in the lungs. Sometimes the victim will actually swallow the soot. In these cases, traces can be found in the esophagus and the lining of the stomach.

The ultimate cause of a death from hanging is typically the ces- sation of blood fl ow to or from the brain. Victims of hangings may show signs of petechiae on the eyelids, along with a swollen and a blue/purplish appearance of the face. Petechiae are very small and are caused by blood having escaped into the tissues as a result of capillaries bursting (see Figure 3 ). Although petechiae are wit- nessed in hanging cases, they are more common in strangulation deaths. Typi- cally the hyoid bone (the bone on which the tongue rests) and thyroid cartilage (located below the hyoid) are not fractured in cases of hanging. A break of the thyroid cartilage is common, however, in manual strangulation cases.

In hangings it is vitally important to document exactly how the victim was  initially found and the position of the encircling noose, as shown in Figure  4 . The type of knot used may strongly support the notion that another person was involved in the hanging. This means that the knot should always be preserved for later examination. Either the noose should be slipped off the victim’s head intact, or the noose should be cut distant from the knot. Defense wounds are common on strangulation victims. Often the marks found on the neck of a victim are the victim’s own, made in the attempt to loosen whatever was constricting his or her neck. Even in cases of hanging by suicide, there can be defensive wounds on the neck.

FIGURE 2 A stab wound. Cour- tesy Rockland County, NY, Medical Examiner’s Offi ce. © All rights reserved.

petechiae Pinpoint hemorrhaging often observed in the white area of the victim’s eyes; often observed in strangulation cases.

FIGURE 3 Petechial hemorrhages in a victim’s eye. Courtesy Rockland County, NY, Medical Examiner’s Of- fi ce. © All rights reserved.

FIGURE 4 A ligature pattern on a neck with corresponding ligature. Courtesy Rockland Sheriff’s Offi ce, Rockland County, New City, NY. © All rights reserved.

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Smothering can occur by various materials that block the mouth, nose, and internal airway. Pillows or a hand can inhibit breathing. Gags that are used to silence a victim can be sucked into the airway and block oxygen fl ow. Typically a death by smothering is homicidal in nature. Accidental smothering usually occurs only in infants or in cases where a victim is trapped under an obstruction.

GUNSHOT WOUNDS When evaluating a gunshot wound, the esti- mated range of fi re is one of the most important characteristics to analyze ( Figure 5 ). The appearance of the wound can be of help in estimating whether the fi rearm used to infl ict the wound was dis- charged while in contact with the victim’s body or from a distance of only inches to many feet away. The investigator will compare powder residue distribution around the wound to test fi res collected from the infl icting fi rearm to make this estimate. Obviously if the fi rearm was fi red at a distance of several feet, suicide is a highly unlikely cause of death because the wound could not have been self-infl icted. Gun- powder residue on the victim’s hand, as shown in Figure 6 , is a pos- sible indicator of suicide, but this is not always the case. Evidence of contact shots, that is, shots fi red with the gun held against the body of

the victim, typically indicates that the death was not an accident. The autopsy must include a determination of the path or “wound track” of the projectile. The wound track is determined by observing the wound from the outside of the body, follow- ing the track of the projectile through the body, and documenting its terminus. The pathologist will recover any and all projectiles from the body, carefully pro-

tecting its forensic markings. The autopsy of gunshot victims should include several facts in addition to the general autopsy facts: Scene investigation and the results of toxicological and serological analyses are important. All fi ndings regarding the bullet wounds should be noted, as well as descriptions of the clothing. The police report with a thorough description of the scene is also important.

A gunshot wound may not necessarily explain why a victim died. A person who sustains a gunshot wound can bleed to death in a matter of minutes or up to several hours. Infection can also be a contributory cause of death, especially in cases where the victim was shot in the abdomen: He or she might live several days but

eventually succumb to infection. In cases where the victim was shot in the head but survives in a comatose state, pneumonia often develops. These intervening factors are considered contributory causes of death, but the gunshot wound is still considered the underlying cause of death.

SUBSTANCE ABUSE Drug abuse continues to be an enormous problem in the United States. Drug enforcement is a multibillion-dollar industry. Many of the abused drugs in the country are illegal, but not all are. Deaths as a result of substance abuse are common cases that a forensic pathologist must face. Because drug abuse is so common, the forensic pathologist will routinely test for the presence of drugs in nearly all investigations, and routine tests are available for many commonly abused drugs. As technology has improved, many drugs can be detected at very low levels. These factors have helped considerably in making substance abuse testing easier and less expensive.

Drug abuse can directly cause death, or it can cause complications that can serve as a contributing factor to death. An abuser can misuse a drug or a number of drugs for years, accumulating detrimental effects in that time. Death as a result of those effects is typically labeled a natural death by the pathologist. Drugs can also alter a person’s judgment and psychomotor skills to the point that a fatal accident occurs. Drugs are also often at the source of acts of violence that result in death.

FIGURE 5 A contact gunshot wound to the temple of a suicide victim. Courtesy Rockland County, NY, Medical Examiner’s Offi ce. © All rights reserved.

FIGURE 6 Powder residue on the hand of a suicide victim. Courtesy Rockland County, NY, Medical Examiner’s Offi ce. © All rights reserved.

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Quick Review • A primary objective of the autopsy is to determine the cause of death. The

cause of death is that which initiates the series of events ending in death. • The most important determination in a violent death is the character of the

injury that started the chain of events that resulted in death. • Some of the more common causes of death are blunt force injury, sharp

force injury, asphyxia, gunshot wound, and substance abuse. • A blunt force injury is caused by a nonsharpened object such as a bat or

pipe. A blunt force injury can abrade tissue or can cause a contusion aris- ing from bleeding from tiny ruptured blood vessels within and beneath the skin.

• Sharp force injuries occur from weapons with sharp edges, such as knives or blades.

• Asphyxia encompasses a variety of conditions that involve interference with the intake of oxygen. For example, death at a fi re scene is caused primarily by the extremely toxic gas, carbon monoxide.

• Gunshot wounds originate from projectiles fi red by a fi rearm. The distance a weapon was fi red from a target is one of the most important factors in characterizing a gunshot wound.

• Because drug abuse is so common, a forensic pathologist will routinely order toxicological tests for the presence of drugs in nearly all autopsies.

THE AUTOPSY

An autopsy , in its broadest defi nition, is simply the examination of a body after death (i.e., a postmortem examination). The autopsy can be further de- scribed as one of two types: a clinical/hospital autopsy or a forensic/medi- colegal autopsy. The clinical/hospital autopsy focuses on the internal organ fi ndings and medical conditions. Its purpose is to confi rm the clinical diag- noses, the presence and extent of disease, any medical conditions that were overlooked, and the appropriateness and outcome of therapy. In contrast, the goal of a forensic/medicolegal autopsy is to determine the cause of death and confi rm the manner of death, often to be used in criminal proceedings. The forensic autopsy usually emphasizes external and internal fi ndings while de- veloping meaningful forensic correlations between sustained injuries and the crime scene (see Figures 7 and 8 ).

All the steps of the forensic autopsy must be carefully documented and photographed. The documentation should include date, time, place, by whom the autopsy was performed, and who attended the autopsy. Photographs of the injuries, complete with a scale, and descriptions of each photograph’s location are important when correlating external wounds with internal damage. Negative photographs—photographs of uninjured parts of the body—are also important. The autopsy report and photographs are so important because, once the body is buried, no further evidence can be collected and no additional fi ndings can  occur.

EVIDENCE FROM THE AUTOPSY The search for physical evidence must extend beyond the crime scene to the autopsy room of a deceased victim. Here, the med- ical examiner or pathologist carefully examines the victim to establish the cause and manner of death. As a matter of routine, tissues and organs are retained for pathological and toxicological examination. At the same time, arrangements must be made between the examiner and investigator to secure a variety of items that may be obtainable from the body for laboratory examination. The following are among the items to be collected and sent to the forensic laboratory:

• Victim’s clothing • Fingernail scrapings

autopsy A surgical procedure performed by a pathologist on a dead body to ascertain—from the body, organs, and bodily fl uids—the cause of death.

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• Combings from head and public areas • Blood (for DNA typing purposes) • Vaginal, anal, and oral swabs (in sex-related crimes) • Bullets recovered from the body • Swabs of body areas suspected of being in contact with DNA arising

from touching or saliva • Hand swabs from shooting victims (for gunshot residue analysis)

FIGURE 8 Tools used for an autopsy. Courtesy Rockland County, NY, Medical Examiner’s Offi ce. © All rights reserved.

FIGURE 7 An autopsy suite. Courtesy Rockland County, NY, Medical Examiner’s Offi ce. © All rights reserved.

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These items of evidence should be properly packaged and labeled like all other evidence. Once the body is buried, efforts at obtaining these items may prove diffi cult or futile. Furthermore, a lengthy time delay in obtaining many of these items will diminish or destroy their forensic value.

EXTERNAL EXAMINATION The forensic autopsy consists of an external exami- nation and an internal examination. The fi rst steps taken for the external exam- ination include a broad overview of the condition of the body and the clothing. Obvious damage to the clothing should be matched up to injuries on the body. General characteristics of the body should be noted, including sex, height, weight, approximate age, color of hair, and physical condition. The presence of tattoos and scars, as well as puncture and track marks, are noted. All evidence of apparent medical intervention must be carefully noted, described, and pho- tographed because occasionally these may be misinterpreted, especially chest tube insertions and emergency cardiac punctures. The mouth and nose is ex- amined for the presence of vomit and/or blood and trace evidence, and the ears are examined for blood. Any irritations in the nasal cavity can be indicative of drug sniffi ng.

Often, paper bags are place over the hands at the crime scene until it is time to examine them. This prevents contamination and possible loss of trace evidence, such as hairs and fi bers. This preservation of evidence can play an important role in identifying a suspect. A victim will sometimes have skin and DNA under his or her fi ngernails from fi ghting with the assailant.

The external examination also consists of classifying the injuries. This includes distinguishing between different types of wounds, such as a stab wound versus a gunshot wound. The injuries that are examined may include abrasions, contusions, lacerations, and sharp injury wounds. Hemorrhages in the eyelids (petechiae) are also essential to note, as they can be indicative of strangulation. Attention is also paid to the genitalia, especially in cases where sexual abuse is suspected. In these cases, vaginal, oral, and rectal samples are taken.

The discharge from a fi rearm will produce characteristic markings on the skin. This discharge is a combination of soot and gunpowder. It will leave markings called stippling or tattooing around the bullet hole. The stippling can be analyzed in terms of its span and density in order to approximate the range of fi re. The range of fi re may prove to be the most important factor in distin- guishing a homicide from a suicide.

X-ray examinations can be very useful in the autopsy process. They are most commonly performed in gunshot wound cases and stab wound cases. Even if the bullet, knife, or other piercing weapon is recovered outside the body, an X-ray will identify any fragments still inside the body. An X-ray will also help determine the path of the projectile or sharp utensil. X-rays can also be very helpful in cases where the victim was beaten, especially situations in which the victim is a child: An X-ray can show past bone fractures and a possible pattern of abuse.

INTERNAL EXAMINATION The dissection of the human body generally entails the removal of all internal organs through a Y-shaped incision beginning at the top of each shoulder and extending down to the pubic bone. Performing the internal examination entails weighing, dissecting, and sectioning each organ of the body. When required and in accordance with jurisdictional rules, microscopic examination of the sectioned organs is conducted, which can help in determining the cause of death. For example, microscopic examination of lungs and liver can confi rm chronic intravenous drug abuse. Examination of the cranium requires cutting an incision from behind one ear to the other, peeling the scalp upward and backward, and sawing of the skull in a circular cut; then the skull cap is removed to reveal the brain, as shown in Figure 9 .

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Special care is taken to identify any preexisting conditions or malformations in the organs that might have contributed to the death of the victim. Pulmonary edema (fl uid accumulation in the lungs) is frequently found in victims of chronic cocaine and amphetamine abuse. Heart malformations may cause suspicious death in an otherwise healthy individual.

Special attention is paid to the digestive tract if poi- soning is suspected. The stomach can show partially digested or dissolved pills. Chemical analyses can also be carried out to show signs of poisoning. The amount of pills or tablets in the stomach can aid in the determi- nation of manner of death as well. It is not always a sure sign, but typically it is unlikely that a person will acciden- tally swallow a large number of pills. This would suggest suicide rather than an accidental overdose. Stomach contents may reveal the deceased’s last meal. The extent of digestion can help with determining the time of death.

Toxicology The internal examination is also where toxicological specimens are taken. These include samples of blood, stomach content, bile, and urine. All bile in the gallbladder and all stomach content are collected. In addition to these, brain matter, liver, and

vitreous humor are also gathered. These specimens can play especially large roles in cases where poisoning or drug abuse is suspected.

Blood is often tested to determine the presence and levels of alcohol and drugs. Blood should be taken from areas of the body where there is the least chance of contamination. Blood should never be collected from body cavities, where it may be contaminated from adjacent structures. Many changes oc- cur in the body after death, and these changes can alter the drugs present in the system at the time of death. This can make interpreting how much of a drug was present, if any at all, a very challenging task. Some drugs redistrib- ute or reenter the blood after death and thus may complicate the interpreta- tion of postmortem blood levels of these drugs. This phenomenon is known as postmortem redistribution. For this reason, it is best to collect blood at distant areas of the body to allow the toxicologist to compare the agreement of the drug concentrations found. The ideal location to retrieve the blood is internally, directly from the inferior vena cava (the large vein inside the lower abdominal region, which receives its blood from the femoral veins) using a syringe. Where postmortem redistribution of drugs may have occurred, blood should also be collected at autopsy from the superior venous system directly above the heart.

For illicit as well as legal substances, it is necessary to know what levels are indicative of therapeutic use and what levels indicate toxicity of a given substance. Much information regarding therapeutic versus toxic drug levels has been pub- lished. This data can help pathologists and toxicologists ascertain the cause of death. Most drug-related deaths are quite apparent from the blood concentrations of alcohol and/or a drug found in the postmortem toxicological report. (Note that depressant drugs will act in concert with alcohol.) However, in some cases of drug- induced death, drug levels may not always provide evidence. Cocaine is a prime example of this. Cocaine-induced sudden death is an event with an incubation period. Structural alterations of the cardiovascular system are required, and such alterations take months, or perhaps years, of chronic cocaine use. In these individ- uals, death and toxicity may occur after the use of even a trivial amount of the drug.

Unlike drug analyses, general testing for poisons is not a routine procedure carried out by the pathologist. However, if a specifi c poison is suspected,

FIGURE 9 A brain during au- topsy. Courtesy Rockland County, NY, Medical Examiner’s Offi ce. © All rights reserved.

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a particular test must be performed. A body that displays a cherry-red discoloration often leads a pathologist to suspect carbon monoxide poisoning. The pathologist would then perform a toxicological test of the blood. Poison- ing by cyanide could also produce a pinkish discoloration. Often, cyanide toxicity will show additional signs, such as a distinct smell of burnt almonds. Corrosion around the lips of a victim may lead to a suspicion of ingesting an acid or alkaline substance.

Quick Review • An autopsy, in its broadest defi nition, is simply the examination of a body

after death. • The forensic autopsy consists of an external examination and an internal

examination. • The fi rst steps taken for the external examination include a broad overview

of the condition of the body and the clothing. • The external examination also consists of classifying the injuries. This

includes distinguishing between different types of wounds, such as a stab wound versus a gunshot wound.

• The dissection of the human body generally entails the removal of all internal organs through a Y-shaped incision beginning at the top of each shoulder and extending down to the pubic bone.

• The internal examination entails weighing, dissecting, and sectioning each organ of the body.

• Blood is often routinely tested to determine the presence and levels of alcohol and drugs.

• Some drugs redistribute or reenter the blood after death and thus may complicate the interpretation of postmortem blood levels of these drugs.

MANNER OF DEATH

The manner of death relates to the circumstances that led to the fatal result and is the culmination of the complete investigation, including the determina- tion of cause of death. The certifi cation of the circumstances and manner of death is the responsibility of the coroner’s and medical examiners’ offi ces. The manner in which death occurred is classifi ed in death certifi cations as one of fi ve categories: homicide , suicide, accidental, natural, or undetermined .

HOMICIDE Although there is no universal agreement on its defi nition, generally the term homicide , as certifi ed by coroner’s and medical examiners’ offi ces, is defi ned as a nonaccidental death resulting from grossly negligent, reckless, or intentional actions of another person. Both the cause and manner of death, as certifi ed by the coroner’s/medical examiners’ offi ces, can become the subject of expert debate during any subsequent judicial proceedings. However, this does not result in a revision of the death certifi cation unless there has been negligence on the part of the certifying offi ces.

If the pathologist was unable to go to the scene, he or she should receive adequate information detailing the conditions of the scene from coroner/ medical examiner investigators and law enforcement personnel. This information should include how the body was discovered as well as when and where. It is also an important fi rst step for investigators to make note of the algor mortis, livor mortis, and/or rigor mortis of the body at the scene. These will help to determine time of death.

SUICIDE Suicide is the result of an individual taking his or her own life with lethal intention. For a determination of suicide, it must be demonstrated that the individual carried out the act alone. If there is any doubt about the

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manner of death A determination made by a forensic pathologist of the cause of death. Five broad categories are homicide, suicide, accidental, natural, and undetermined.

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intentions of the victim, the death is not classifi ed as a suicide; the death is ruled as an accident or even as undetermined. The most common methods of suicide include self-infl icted gunshot wounds, hanging, and drug overdosing. Although drug abuse is deliberately committed by a victim, it is not consid- ered suicide unless it was clearly intended as a lethal act.

There are various challenges associated with discriminating suicide from an accident or even homicide. The victim’s personal history, including his or her psychiatric history, becomes relevant. Suicidal threats or past attempts would give obvious evidence of a suicide as opposed to an accident. In all cases of suspected suicide, a thorough search of the victim’s possessions should be made to locate a suicide note.

Multiple gunshot wounds might lead one to suspect homicide. However, a person that is committed to ending his or her own life may take several shots if the wounds are not instantly fatal. It is imperative to confi rm that it is physically possible that the victim could infl ict the wounds. There are a few areas of the body that strongly point toward homicide. These are areas that are not easily accessible to the victim’s own reach. For example, anywhere on the back of a victim is diffi cult and sometimes impossible for the victim to have shot by his or her own hand. This is especially true if the wound was made in the back of the head. For suicides, the most common shot is to the temple of the head. The mouth, forehead, and chest are also common.

Also, if the wound was immediately incapacitating, the weapon should be present. Blood spatter analysis should be consistent with the proposed order of events. All victims involved in gunshot cases should have their hands swabbed for gunshot residue.

ACCIDENTAL In all deaths that are ruled accidental, there must not be intent to cause harm through gross negligence on the part of a perpetrator or the victim. Traffi c accidents make up a large percentage of accidental deaths, followed by drug overdoses and drownings. The surviving driver may have vehicular homicide charges brought against him or her, especially if the driver is determined to have been driving under the infl uence of drugs or alcohol. In this case, the offi cial manner of death certifi ed on the death certifi cate in many jurisdictions would be vehicular homicide .

All cases that have the possibility of being a ruled an accident should have toxicological analyses carried out. The presence of drugs and/or alcohol in the victim’s system can potentially affect the determination. Also, the pathologist should be aware that some events might be disguised as accidents to cover up a homicide or suicide. For example, bodies recovered from a house fi re might show evidence that the victims were dead before the fi re started. This evidence might include a lack of soot in the victim’s airways or no indication of elevated levels of carbon monoxide. This scenario, although not common, illustrates how the autopsy and scene can apparently not correlate with each other. No matter how obvious a scene may appear, the two should always correspond with one another. Cases of electrocution are generally ruled as accidents, but this may be diffi cult to prove. High-voltage electrocutions will usually leave burns on the body. Low-voltage electrocutions, however, may show little to no signs of trauma. The scene then becomes crucial in ascertain- ing the events surrounding the death.

The determination of manner of death in drownings (accidental, suicidal, or homicidal), falls (accidental, pushed, or deliberate), and asphyxiations can be exceedingly diffi cult, and therefore the investigation in all of its components becomes much more important than the autopsy.

NATURAL CAUSES The differentiation between the categories of manner of death can be diffi cult to make. The distinction between natural and accidental deaths can pose challenges. The classifi cation of natural death includes disease

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and continual environmental abuse. This abuse can encompass various events, such as chronic drug and alcohol abuse or longtime exposure to natural toxins or asbestos. Again, although drug abuse is deliberately committed by the victim, a death caused by drug use is not considered suicide unless it is clear that drugs were taken as an intentionally lethal act. Acute ethanol intoxication can be ruled as either natural or accidental depending on the circumstances. If the victim suffers from chronic alcoholism, the death is ruled to be natural. If the victim is a teenager experimenting with alcohol for the fi rst time, the death is ruled an accident.

UNDETERMINED A death is ruled to be undetermined only when a rational classifi cation cannot be established. This can happen when the mechanism that caused the death cannot be determined by a physical fi nding at the autopsy or because of the absence of meaningful fi ndings in the subsequent toxicological and microscopic examinations.

Quick Review • The manner in which death occurred is classifi ed in death certifi cates as one

of fi ve categories: homicide, suicide, accidental, natural, or undetermined. • Homicide is generally defi ned as a nonaccidental death resulting from

grossly negligent, reckless, or intentional actions of another person. • Suicide is the result of an individual taking his or her own life with lethal

intention. Although drug abuse is deliberately committed by a victim, it is not considered the cause of suicide unless it was clearly intended as a lethal act.

• In all deaths that are ruled accidental, there must not be intent to cause harm through gross negligence on the part of a perpetrator or the victim. Traffi c accidents make up a large percentage of accidental deaths, followed by drug overdoses and drownings.

• The classifi cation of natural death includes disease and continual environ- mental abuse. This abuse can encompass various events, such as chronic drug and alcohol abuse or longtime exposure to natural toxins or asbestos.

• An undetermined cause of death arises when the cause of death cannot be determined by a physical fi nding at the autopsy or because of the absence of meaningful fi ndings in the subsequent toxicological and microscopic examinations.

ESTIMATING TIME OF DEATH

A pathologist can never give an exact time of death. However, there are many characteristics that the examiner can analyze in order to arrive at an approxi- mate time of death. Some features can give a very probable time of death, but others are extremely variable. Witnesses can serve to reconstruct the events leading up to the death and the incidents that occurred after the death, along with the times when they occurred, but a single witness’s account alone is not enough to make an accurate determination. The chemical and physical changes that occur after death must also be examined.

ALGOR MORTIS After death the body undergoes a process in which it contin- ually adjusts to equalize with the environmental temperature. This process is known as algor mortis . An algor mortis determination must be performed at the scene as early as possible. The fi rst step is to determine as best as possible what the environmental temperatures may have been prior to discovering the body. Then the environmental temperature and the bilateral axillary and/or ear canal temperatures are recorded at the crime scene (rectal temperatures are usually too disruptive at the scene). The cooling rate of a typical body can

algor mortis A process that occurs after death in which the body temperature continually cools until it reaches the ambient or room temperature.

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DEATH INVESTIGATION

be used to estimate the time of death. At average ambient temperatures of 70°F �72°F, the body loses heat at a rate of approximately of 1.0°F to 1.5°F per hour until the body reaches the ambient or room temperature. However, the rate of heat loss is infl uenced by factors such as ambient temperature, the size of the body, and the victim’s clothing. Because of such factors, this method can only approximate the amount of time that has elapsed since death.

LIVOR MORTIS Another condition that begins when circulation ceases is livor mortis . When the human heart stops pumping, the blood begins to settle in the parts of the body closest to the ground. As shown in Figure  10 , the skin becomes a bluish-purple color in these areas. The onset of this con- dition begins twenty minutes to three hours after death and under average conditions continues for up to sixteen hours after death, at which point all

lividity, or coloring, is fi xed. Initially, lividity can be pressed out of the vessels when the skin is pressed, that is, lividity can be “blanched.” With time, coloring becomes “fi xed” in the vessels, beginning in the most dependent (lowest) areas and progressing to the least dependent areas, then fi nally no blanching can be elic- ited anywhere. In any case, levels of lividity are tested at the scene with regard to whether it is completely fi xed, blanches when sub- jected to light pressure, or blanches when subjected to signifi cant pressure. A  range of time of death can be estimated if at least some of the lividity is still blanching. However, the environmental temperature and the rate of body temperature decline (i.e., algor

mortis) directly affect the rate of fi xation of lividity and therefore must be taken into account when attempting to estimate time of death from lividity.

Different lividity patterns in a body may indicate that the body was moved after death, but before livor mortis had fully fi xed. The skin does not become discolored in areas where the body is restricted by either clothing or an object pressing against the body. This information can be useful in determining whether the victim’s position was changed after death. Livor that is a deep purple is often seen in cases where the victim suffered asphyxia or heart failure.

RIGOR MORTIS Immediately following death, a chemical change occurs in the muscles that causes them to become rigid, as shown in Figure 11 . This condition,

livor mortis A medical condition that occurs after death and results in the settling of blood in areas of the body closest to the ground.

FIGURE 10 Livor mortis. Courtesy Rockland County, NY, Medical Examiner’s Offi ce. © All rights reserved.

FIGURE 11 Rigor mortis in the arms of a decedent. Courtesy Rockland County, NY, Medical Examiner’s Of- fi ce. © All rights reserved.

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rigor mortis , evolves over the fi rst twenty-four hours under average tempera- ture and body conditions. This rigidity subsides as time goes on, however, and disappears after about thirty-six hours under average conditions. Rigor will de- velop in the position that the body was in at the time of death, essentially freez- ing the body in that pose. Discovering a body in a position that defi es gravity is a likely indicator that the body was moved after death.

Although rigor mortis can roughly indicate a time of death, there are factors that can alter this determination. An environment that is hot can speed up the process signifi cantly. Conditions that affected the body before death, such as exercise or physical activity, can also speed up the process. Because rigor mortis occurs as a result of the muscles stiffening, individuals with decreased muscle mass may not develop rigor completely. Examples of these individuals may be infants or elderly or obese persons.

POTASSIUM EYE LEVELS Another approach helpful for estimating the time of death is to determine potassium levels in the decedent’s ocular fl uid, that is, the fl uid within the eye, also known as the vitreous humor . It is important to draw a clean, bloodless vitreous sample from one eye with a syringe as soon as possible at the scene, then draw a second sample from the other eye an hour or two later. After death, cells within the inner surface of the eyeball release potassium into the ocular fl uid. By analyzing the amount of potassium present at various intervals after death, the forensic pathologist can determine the rate at which potassium is released into the vitreous humor and use it to approximate the time of death. However, the rate of potassium release also is dependent on ambient temperatures.

STOMACH CONTENTS Special attention must be paid to the digestive tract. The identifi cation of food items in the stomach may help to determine the location of the decedent prior to death (during his or her last meal). The quantity, con- sistency, and color of bile, and the degree of digestion of food in the stomach and its passage into the small intestine can help to determine the time of death. The stomach also can contain partially digested or dissolved pills. Chemical analyses can be carried out to identify and analyze substances found in the stomach. These can aid in the determination of cause, and manner of death.

DECOMPOSITION Once decomposition has set in, the preceding methods of determining time of death are no longer of any use. After death, two decomposition processes take place: autolysis and putrefaction. Autolysis is fundamentally self-digestion by cells’ own enzymes, and its rate varies from organ to organ depending on the mechanism of death, the enzyme content of the respective organs, the position of the body, and environmental factors. Putrefaction is decomposition carried out by microorganisms such as bacteria. Putrefaction is accompanied by bloating, discoloration, and a foul smell caused by accumulating gases. Again, the rate of putrefaction is dependent on the mechanism of death (for example, congestive respiratory versus sudden cardiac death) allowing bacteria to spread from the bowel, presence or absence of infection, environmental temperatures and humidity, degree of obesity, extent of clothing, and so on. Green discoloration often begins in the abdo- men. Darker green or purple discoloration follows on the face. The skin begins to blister with gas and then peel (called slippage ). The skin of the hands and feet can actually detach and come off the body like a glove. This stage is also accom- panied by bloating, which causes the eyes to bulge and the tongue to protrude. The chest and extremities will then turn a green/purple discoloration and bloat.

In the postmortem period of decomposition, a waxy substance called adipocere may form. Adipocere adds a white or gray waxlike consistency to fatty tissues in the face and extremities that can take on a yellow to tan color. Typically, adipocere takes about three months to develop.

rigor mortis A medical condition that occurs after death and results in the stiffening of muscle mass. The rigidity of the body begins within twenty-four hours of death and disappears within thirty-six hours of death.

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Quick Review • After death the body undergoes a process known as algor mortis in which

it will continually adjust to equalize with the environmental temperature. • Another condition beginning when circulation ceases is livor mortis.

When the human heart stops pumping, the blood begins to settle in the parts of the body closest to the ground. The skin becomes a bluish-purple color in these areas.

• Immediately following death, a chemical change known as rigor mortis occurs in the muscles, causing them to become rigid.

• Another approach helpful for estimating the time of death is to measure potassium levels in the ocular fl uid.

• The identifi cation of food items in the stomach may help to determine the location of the decedent prior to death, during his or her last meal.

Role of the Forensic Anthropologist Forensic anthropology is concerned primarily with the identifi cation and examination of human skeletal remains. Skeletal bones are remarkably du- rable and undergo an extremely slow breakdown process that lasts decades or centuries. Because of their resistance to decomposition, skeletal remains can provide a multitude of individual characteristics long after a victim’s death. An examination of bones may reveal a victim’s sex, approximate age, race, height, and the nature of a physical injury.

RECOVERING AND PROCESSING REMAINS

Thorough documentation is required throughout the processes of recovery and examination of human remains. A site where human remains are found must be treated as a crime scene (see Figure 12 ). These sites are usually located

forensic anthropology The use of anthropological knowledge of humans and skeletal structure to examine and identify human skeletal remains.

FIGURE 12 Crime-scene site showing a pelvis partly buried in sand and a femur lying across a revolver. Courtesy Paul Sledzik/National Transportation Safety Board

140

DEATH INVESTIGATION

by civilians who then contact law enforcement personnel. The scene should be secured as soon as possible to prevent any further alteration of the scene. The scene should then be searched to locate all bones, if they are scattered, and any other items of evidence such as footwear impressions or discarded items. There are many tools that can be useful when searching for evidence at a “tomb” site, including aerial photography, metal detectors, ground-penetrat- ing radar, infrared photography, apparatuses that detect the gases produced by biological decomposition, and so-called cadaver dogs that detect the odors caused by biological decomposition. All items that are found must be tagged, photographed, sketched, and documented in notes. Once all bones and other evidence are found, a scene sketch should be made to show the exact location of each item (preferably using global positioning system [GPS] coordinates), and the spatial relationship of all evidence. Once the skeletal remains have been recovered, they can be examined to deduce information about the iden- tity of the decedent.

DETERMINING VICTIM CHARACTERISTICS

The sex of the decedent can be determined by the size and shape of various skeletal features, especially those of the pelvis and skull, or cranium. Female pelvic bones tend to form a wider, more circular opening than that in a male pelvis because of a woman’s child-bearing capabilities. The female sacrum (fl at bone above the tailbone) is wider and shorter (see Figure 13 [a]) than a male’s; the length and width of the male sacrum are roughly equal (see Figure  13 [b]). The angle formed at the bottom of the pelvis (i.e., subpubic angle) is approximately a right angle (90 degrees) in females, but it is acute (less than 90 degrees) in males. In general, male craniums are larger in overall size than those of females. A male cranium tends to have a more pronounced brow bone and mastoid process (a bony protrusion behind the jaw) than a female cranium (see Figure 14 ). See Table 1 for a summary of the differing features of female and male skeletons from head to toe. These are typical cases; not all skeletons may display the given characteristics to clearly indi- cate the sex of the decedent.

The method for determining the age of a decedent varies depending on the victim’s growth stage. For infants and toddlers, age can be estimated by

FIGURE 13 (a) Frontal shot of female pelvis and hips. This view shows the wide, circular nature of the pelvic opening and the short, wide nature of the sacrum. (b) Human male pelvis. This view shows the narrow pelvic opening and long, narrow sacrum. (b) Giuliano Fornari © Dorling Kindersley

(a) (b)

141

DEATH INVESTIGATION

the length of the long bones (e.g., femur and humerus) when compared to a known growth curve. Different sections of the skull also fuse together at differ- ent stages during early development, and the appearance of fused or divided sections can be used to estimate the age of bones still in early developmental stages (see Figure 15 ). In infant skeletons, formation of teeth can be used in age determination; this is based on the fact that permanent teeth start to form

FIGURE 14 Male (left) and female (right) human skulls showing male skull’s larger size and more pronounced brow bone. Corbis RF

TABLE 1 Summary of Skeletal Features by Gender

  FEMALE MALE

Cranium (skull) Medium to large in size Large in size

Forehead High in height, vaulted, rounded Low in height, sloped, backward

Brow bone Diminished Pronounced

Mastoid process Diminished or absent Pronounced

Mandible (jaw) angle Obtuse (�90 degrees) Approximately right (90 degrees)

Pelvis opening Wide, circular Narrow, noncircular

Sacrum Short, wide, turned outward Approximately equal width/length, turned inward

Subpubic angle Approximately right (90 degrees) Acute (�90 degrees)

Femur Narrow, angled inward from pelvis Thick, relatively straight from pelvis

Overall skeleton Slender Robust

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DEATH INVESTIGATION

at birth. If the skeletal remains belong to a child, the age of the decedent may be determined by observing the fusion or lack of fusion of epiphyseal regions of bones such as those of the mandible (i.e., lower jaw), fi ngers, wrist, long bones, and clavicle (see Figure 16 ). The average age at which each of these

FIGURE 15 A lateral view of a fetal skull showing the separated bones of the skull before they have had a chance to fuse. Ralph T. Hutchings

FIGURE 16 Colored X-rays of healthy human hands at 3 years (left) and at 20 years. Bones display in red, and fl esh is in blue. The child’s hand has areas of cartilage in the joints between the fi nger bones (i.e., epiphyseal areas), where bone growth and fusion will occur. In the adult hand, all the bones are present, and the joints have closed. SPL\Photo Researchers Inc.

143

DEATH INVESTIGATION

regions fuses is known and can be compared against the state of the remains to provide a range of possible ages for the decedent. A child’s cranium may also be identifi ed by its smaller size and the presence of developing teeth (see Figure 17 ). After age 21, age is estimated by the level of change the surfaces of the bones have undergone, especially in areas of common wear such as the pubic symphysis. The pubic symphyseal face shown in Figure 18 is a raised platform that slowly changes over the years from a rough, rugged surface to a smooth, well-defi ned area. See Table 2 for a summary of the skeletal closures by age. It is important to note that these are average ages for closures; not all skeletons display closures at the given ages.

Although the categorization “race” has come under scrutiny and is diffi cult to defi ne, forensic anthropologists use broad classes to characterize the likely (but not defi nite) ancestry of skeletal remains. The possible racial ancestry of the decedent can be assessed by the appearance of various cranial features on the skeletal remains. For example, eye orbits tend to be circular in Mongoloid skeletons (i.e., of Asian descent), oval in Caucasoid skeletons (i.e., of European descent), and square in Negroid skeletons (i.e., of African descent). The frontal plane of the cranium may also vary. The frontal plane of Mongoloid craniums may be fl at or projected outward, that of Caucasoid craniums is fl at, and that of Negroid craniums is projected outward. The nasal cavity tends to be small and rounded in Mongoloids, long and narrow in Caucasoids, and wide in Ne- groids. Skeletal remains of decedents of Asian ancestry, including those of Native American descent, also tend to have “scooped-out” or shovel-shaped incisor teeth. See Table  3 for a summary of the differing features of skeletons that can indicate ancestry. These are typical cases; not all skeletons may dis- play the given characteristics to indicate the ancestry of the decedent.

The height of the victim when alive can be estimated by measuring the long bones of the skeleton, especially in the lower limbs. Even partial bones can yield useful results. However, meaningful stature calculations from known equations must be based on the determined sex and race of the remains. See Table 4 for examples of equations used to calculate the height of the dece- dent from skeletal remains. These equations should yield estimations within 5 cm of actual height.

FIGURE 17 The skull of a young child, with part of the jaw cut away to show the developing teeth. Ralph T. Hutchings

FIGURE 18 The symphysis pubis shown magnifi ed beneath human pelvic bones. Pearson Education Custom Publishing

144

DEATH INVESTIGATION

TABLE 2 Summary of Skeletal Closures by Age

AGE (MONTHS) CLOSURE

6–9 Mandible (jaw) fused

4–6 Humerus head bones fused

7–8 Pelvis frontal bones fused

4–16 Femur shaft sections built

9–13 Elbow bones fused

10 Finger bones fused

16–18 Femur head bones fused to shaft bones

18 Wrist bones fused

18–21 Humerus head bones fused to shaft bones

18–24 Sternum fused to clavicle

20–25 Pelvic bones fully formed

21–22 Clavicle fused

21–30 Labodial suture (rear of cranium) fused

24–30 Sacrum bones fused

30–32 Sagittal suture (center of cranium) fused

48–50 Coronal suture (front of cranium) fused

TABLE 3 Summary of Skeletal Characteristics Indicating Racial Ancestry

  EYE ORBITALS NASAL CAVITY INCISORS CRANIUM FRONTAL PLANE

Caucasoid Oval Long, narrow Smooth Flat

Mongoloid Circular Small, rounded Shoveled interior Flat or projected outward

Negroid Square Wide Smooth Projected outward

OTHER CONTRIBUTIONS

OF FORENSIC ANTHROPOLOGY

A forensic anthropologist may create facial reconstructions to help identify skeletal remains. Facial reconstruction clay is placed and shaped over the vic- tim’s actual cranium, and it takes into account the decedent’s estimated age, ancestry, and sex (see Figure 19 ). With the help of this technique, a composite of the victim can be drawn and advertised in an attempt to identify the victim.

Forensic anthropologists are also helpful in identifying victims of a mass disaster such as a plane crash. When such a tragedy occurs, forensic

145

DEATH INVESTIGATION

anthropologists can help identify victims using the collection of bone fragments. Usually, the identifi cation of the remains will depend on medical records, especially dental records of the individuals. However, defi nite identi- fi cation of remains can be made only by analyzing the decedent’s DNA profi le, fi ngerprints, or medical records. Recovered remains may still contain some soft tissue material, such as the tissue of the hand, which may yield a DNA profi le for identifi cation purposes. If the tissue is dried out, it may be possible to rehydrate it to recover fi ngerprints also.

TABLE 4 Equations for Height Calculation from Skeletal Remains

  CAUCASOID NEGROID UNKNOWN ANCESTRY

Female Height (cm) � femur length (cm) � 2.47 � 54.10

Height (cm) � femur length (cm) � 2.28 � 59.76

Height (cm) � femur length (cm) � 3.01 � 32.52

  Height (cm) � humerus length (cm) � 3.36 � 57.97

Height (cm) � humerus length (cm) � 3.08 � 64.67

Height (cm) � humerus length (cm) � 4.62 � 19.00

Male Height (cm) � femur length (cm) � 2.32 � 65.53

Height (cm) � femur length (cm) � 2.10 � 72.22

Height (cm) � femur length (cm) � 2.71 � 45.86

  Height (cm) � humerus length (cm) � 2.89 � 78.10

Height (cm) � humerus length (cm) � 2.88 � 75.48

Height (cm) � humerus length (cm) � 4.62 � 19.00

CASEFILES IDENTIFYING A SERIAL KILLER’S VICTIMS

The worst serial killer in the United States calmly admitted his guilt as he led investigators to a crawl space under his house. There, John Wayne Gacy had buried 28 young men, after brutally raping and murdering them in cold blood. Because no forms of identifi cation were found with the bodies, the police were forced to examine missing-person reports for leads. However, these boys and men were so alike in age, race, and stature that police were unable to individu- ally identify most of the victims. Clyde Snow, the world-renowned forensic anthropologist from Oklahoma, was asked to help the inves- tigators make these diffi cult identifi cations.

Snow began by making a thirty-fi ve-point examination of each skull for comparison to known individuals. By examining each skeleton, he made sure each bone was correctly attributed to an individual. This was crucial to later efforts because some of the victims had been buried on top of older graves, mingling their remains. Once Snow was sure all the bones were sorted properly, he began his in-depth study. Long bones such as the femur (thigh bone) were used to estimate each individual’s height. This helped narrow the search in the attempt to match the victims with the descriptions of missing people.

After narrowing the list of missing people to those fi tting the general description, investigators consulted missing persons’ hospital and dental records. Evidence of injury, illness, or surgery and other unique skeletal defects of the victims were matched to information in the records to make identifi cations. Snow also pointed out features that gave useful clues to the victim’s behavior and medical history. For example, he discovered that one of Gacy’s victims had a healed fracture on his left arm, and that his left scapula (shoulder blade) and arm bore the telltale signs of a left-handed individual. These details were matched to a missing-person report, and another young victim was identifi ed.

For the most diffi cult cases, Snow called in the help of forensic sculptor and facial reconstructionist Betty Pat Gatliff. She used clay and depth markers to put the “fl esh” back on the faces of these forgotten boys in the hopes that someone would recognize them after the photographs of the reconstructed faces were released to the media. Her efforts were successful, but investigators found some families unwilling to accept the idea that their loved one was among Gacy’s victims. Even with Gatliff’s help, nine of Gacy’s victims remain unidentifi ed.

146

DEATH INVESTIGATION

Quick Review • Forensic anthropology is concerned primarily with the identifi cation and

examination of human skeletal remains. • The gender of the decedent can be determined by the size and shape

of various skeletal features, especially those of the pelvis and skull, or cranium.

• The height of the victim when alive can be estimated by measuring the long bones of the skeleton, especially those in the lower limbs.

Role of the Forensic Entomologist The study of insects and their relation to a criminal investigation is known as forensic entomology. In practice, forensic entomology is commonly used to estimate the time of death when the circumstances surrounding the crime are unknown. This determination can be carried out by observing the stage of development of maggots or insects’ sequence of arrival.

DETERMINING TIME OF DEATH

After decomposition begins, necrophilious insects, or insects that feed on dead tissue, are the fi rst to infest the body, usually within 24 hours. The most common and important of these is the blowfl y, recognized by its green or blue color. Blowfl y eggs are laid in human remains and ultimately hatch into  maggots, or fl y larvae, that consume human organs and tissues (see Figure  20 ). Typically, a single blowfl y can lay up to 2,000 eggs during its lifetime. The resulting larvae gather and feed as a “maggot mass” on the

FIGURE 19 Trooper Sarah Foster, a Michigan State Police forensic artist, works on a three-dimensional facial reconstruction from an unidentifi ed human skull at Richmond Post in Richmond, MI. Paul Sancya\ AP Wide World Photos

forensic entomology The study of insect matter, growth patterns, and succession of arrival at a crime scene to determine the time since death.

147

DEATH INVESTIGATION

decomposing remains. Forensic entomologists can approximate how long a body has been left exposed by examining the stage of development of the fl y larvae. This kind of determination is best for a timeline of hours to approximately one month because the blowfl y goes through the stages of its life cycle at a known sequence and in known time intervals that span this period. By determining the most developed stage of fl y found on the body, entomologists can approximate the postmortem interval (PMI) , or the time that has elapsed since death (see Figure 21 ). Newly emerged fl ies are of important forensic interest, as they indicate that an entire blowfl y cycle has been completed on the decomposing body. Likewise, empty pupal cases indicate that a fl y has completed its entire life cycle on the body. Flies known as cheese skippers are primarily found on human corpses in the later stages of decomposition, long after the blowfl ies have left the corpse.

Time determinations based on the blowfl y cycle are not always straightforward, however. The time required for each stage of development is affected by environmental infl uences such as geographical location, climate, weather conditions, and the presence of drugs. For example, cold temperatures hinder the development of fl y eggs into adult fl ies. The forensic entomologist must consider these conditions when estimating the PMI.

Information about the arrival of other species of insects may also help determine the PMI. The sequence of arrival of these groups depends mostly on the body’s natural decomposition process. Predator insects generally arrive and prey on the necrophilious insects. Several kinds of beetles will be found, either feeding directly on the corpse’s tissues or as predators feeding on blowfl y eggs and maggots present on the corpse. Next, omnivore insects arrive at the body. These insects feed on the body, on other insects, and on any surrounding vegetation. Ants and wasps are an example of omnivore insects. Last comes the arrival of indigenous insects, such as spiders, whose presence on or near the body is coincidental as they move about their environment.

OTHER CONTRIBUTIONS

OF FORENSIC ENTOMOLOGY

Entomological evidence can also provide other pertinent information. In gen- eral, insects fi rst colonize the body’s naturally moist orifi ces. However, if open wounds are present, they will colonize there fi rst. Although the decomposition processes may conceal wounds, colonization away from natural orifi ces may indicate the locations of wounds on the body. If maggots are found extensively on the hands and forearms, for example, this suggests the presence of defen- sive wounds on the victim. Insects that have fed on the body may also have accumulated any drugs present in the fl esh, and analyzing these insects can yield the identity of these drugs.

If resources allow, all insect evidence should be carefully collected by a forensic entomology expert. When this is not possible, collection should be carried out by an investigator with experience in death investigation. The entire body and the area where insect evidence was found must be photo- graphed and documented before collection. Insect specimens should be taken from each area on the body where they are found and labeled to show where they were collected from.

postmortem interval (PMI) The length of time that has elapsed since a person has died. If the time is not known, a number of medical or scientifi c techniques may be used to estimate it.

FIGURE 20 A scanning electron micrograph of two-hour-old blow- fl y maggots. Dr. Jeremy Burgess/Photo Researchers, Inc.

148

CASEFILES THE DANIELLE VAN DAM MURDER CASE

Sometime during the night of February 1, 2002, 7-year-old Danielle Van Dam disappeared from her bedroom in the Sabre Springs suburb of San Diego, California. On February 27, three and a half weeks later, search- ers found her naked body in a trash-covered lot about 25 miles from her home. Because of the high degree of decomposition of the girl’s remains, the medical examiner could not pinpoint the exact time of the girl’s death. Her neighbor, 50-year-old engineer David Westerfi eld, was accused of kidnapping Danielle, killing her, and dumping her body in the desert. During the subsequent investigation, Danielle’s blood was found on Westerfi eld’s clothes, her fi ngerprints and blood were found in his RV, and child pornography was found on his home computer.

The actual time of the 7-year-old’s death became a central issue during the murder trial. Westerfi eld had been under constant police surveillance since February 4. Any suggestion that Danielle was placed at the dump site after that date would have eliminated him

as a suspect.  Confl icting expert testimony was elicited from forensic entomologists who were called on to estimate when the body was dumped. The forensic entomologist who went to the dump site, witnessed the autopsy, and collected and analyzed insects from both locations estimated that Danielle died between February 16 and 18. A forensic entomologist and a forensic anthropologist both called to testify on behalf of the prosecution noted that the very hot, very dry weather at the dump site might have mummifi ed Danielle’s body almost immediately, thus causing a delay in the fl ies colonizing the body.

The jurors convicted Westerfi eld of the kidnapping and murder of Danielle Van Dam, and a San Diego judge sentenced David Westerfi eld to death. Danielle Van Dam’s parents fi led and settled a wrongful death suit against Westerfi eld requiring his automotive and homeowners’ insurance carriers to pay the Van Dams an undisclosed amount, reported to be between $400,000 and $1 million.

FIGURE 21 Typical blowfl y life cycle from egg deposition to adult fl y emergence. This cycle is representative of any one of nearly ninety species of blowfl ies in North America. Volker Steger/Photo Researchers, Inc.

Eclosion: Adult Fly Emerges

Larva Stage III

Larva Stage III

Postfeeding

Puparium

Early

Late

Oviposition

Egg

Eclosion: Maggot Emerges

Larva Stage I

Larva Stage II

149

DEATH INVESTIGATION

Quick Review • Forensic entomologists can approximate how long a body has been left

exposed by examining the stage of development of fl y larvae on the body. • Information about the arrival of other species of insects may also help

determine the postmortem interval. The sequence of arrival of these groups depends mostly on the body’s natural decomposition process.

• In general, insects fi rst colonize the body’s naturally moist orifi ces. However, if open wounds are present, they will colonize there fi rst.

CHAPTER REVIEW

• Forensic pathologists associated with the medical examiner’s or coroner’s offi ce are responsible for determining the cause of a an undetermined or unexpected death.

• Although both the coroner’s offi ce and the medical examin- ers’ offi ce are charged with investigating suspicious deaths, only the pathologist is trained to perform an autopsy. The tasks of examining the body for cause and manner of death and recording the results in the death certifi cate are all responsibilities of both offi ces.

• Protection of the body and the overall scene is of paramount importance, as is the ultimate removal of the body in a medi- cally acceptable manner.

• A primary objective of the autopsy is to determine the cause of death. The cause of death is defi ned as that which initiates the series of events ending in death.

• The most important determination in a violent death is the character of the injury that started the chain of events that resulted in death.

• Some of the more common causes of death are: blunt force injury, sharp force injuries, asphyxia, gunshot wounds, and substance abuse.

• A blunt force injury is caused by a nonsharpened object such as a bat or pipe. A blunt force injury can abrade tissue or can cause a contusion arising from bleeding from tiny ruptured blood vessels within and beneath the skin.

• Sharp force injuries occur from weapons with sharp edges, such as knives or blades.

• Asphyxia encompasses a variety of conditions that involve interference with the intake of oxygen. For example, death at a fi re scene is caused primarily by the extremely toxic gas, carbon monoxide.

• Gunshot wounds originate from projectiles fi red by a fi rearm. The distance a weapon was fi red from a target is one of the most important factors in characterizing a gunshot wound.

• Because drug abuse is so common, a forensic pathologist will routinely order toxicological tests for the presence of drugs in nearly all autopsies.

• An autopsy, in its broadest defi nition, is simply the examina- tion of a body after death.

• The forensic autopsy consists of an external examination and an internal examination.

• The fi rst steps taken for the external examination include a broad overview of the condition of the body and the clothing.

• The external examination also consists of classifying the injuries. This includes distinguishing between different types of wounds, such as a stab wound versus a gunshot wound.

• The dissection of the human body generally entails the removal of all internal organs through a Y-shaped incision beginning at the top of each shoulder and extending down to the pubic bone.

• The internal examination entails weighing, dissecting, and sectioning each organ of the body.

• Blood is often tested to determine the presence and levels of alcohol and drugs.

• Some drugs redistribute or reenter the blood after death and thus may complicate the interpretation of postmortem blood levels of these drugs.

• The manner in which death occurred is classifi ed in death certifi cations as one of fi ve categories: homicide, suicide, accidental, natural, or undetermined.

• Homicide is generally defi ned as a nonaccidental death re- sulting from grossly negligent, reckless, or intentional actions of another person.

• Suicide is the result of an individual taking his or her own life with lethal intention. Although drug abuse is deliberately committed by a victim, it is not considered a cause of suicide unless it was clearly intended as a lethal act.

• In all deaths that are ruled accidental, there must not be intent to cause harm through gross negligence on the part of a perpetrator or the victim. Traffi c accidents make up a large percentage of accidental deaths, followed by drug overdoses and drownings.

• The classifi cation of natural death includes disease and continual environmental abuse. This abuse can encompass

150

KEY TERMS

various events, such as chronic drug and alcohol abuse or longtime exposure to natural toxins or asbestos.

• An undetermined cause of death arises when the cause of death cannot be determined by a physical fi nding at the autopsy or because of the absence of meaningful fi ndings in the subsequent toxicological and microscopic examinations.

• After death the body undergoes a process known as algor mortis in which it will continually adjust to equalize with the environmental temperature.

• Another condition beginning when circulation ceases is livor mortis. When the human heart stops pumping, the blood begins to settle in the parts of the body closest to the ground. The skin appears bluish-purple in these areas.

• Immediately following death, a chemical change known as rigor mortis occurs in the muscles, causing them to become rigid.

• Another approach helpful for estimating the time of death is to measure potassium levels in the ocular fl uid.

• The identifi cation of food items in the stomach may help to determine the location of the decedent prior to death (i.e., during his or her last meal).

• Forensic anthropology is concerned primarily with the identi- fi cation and examination of human skeletal remains.

• The gender of the decedent can be determined by the size and shape of various skeletal features, especially those in the pelvis and skull, or cranium.

• The height of the victim when alive can be estimated by mea- suring the long bones of the skeleton, especially those in the lower limbs.

• Forensic entomologists can approximate how long a body has been left exposed by examining the stage of develop- ment of the fl y larvae on the body.

• Information about the arrival of other species of insects may also help determine the postmortem interval. The sequence of arrival of these groups depends mostly on the body’s natural decomposition process.

• In general, insects fi rst colonize the body’s naturally moist orifi ces. However, if open wounds are present, they will colonize there fi rst.

algor mortis

autopsy

cause of death

forensic anthropology

forensic entomology

forensic pathologist

livor mortis

manner of death

petechiae

postmortem interval (PMI)

rigor mortis

DEATH INVESTIGATION

REVIEW QUESTIONS

1. The titles of ______________ and ______________ are often used interchangeably, but there are signifi cant differ- ences in their job descriptions.

2. True or False: The medical examiner is an elected offi cial and is not required to possess a medical degree. ______________

3. Although both a coroner and a forensic pathologist are charged with investigating a suspicious death, only the ______________ is trained to perform an autopsy.

4. True or False: If it appears that a victim did not shoot him- or herself or anyone else, the victim’s hands should not be swabbed. ______________

5. The primary objective of the autopsy is to determine the ______________ .

6. True or False: The manner of death is defi ned as that which ini- tiates the series of events ending in death. ______________

7. A(n) ______________ force injury can abrade and crush tissue.

8. True or False: The outward appearance of the injuries will always match the injuries sustained inside the body. ______________

9. Wounds on a victim’s forearm may be ______________ wounds.

10. True or False: A lack of any defense wounds can lead a pathologist to believe that the victim was either unconscious or somehow tied up during the assault. ______________

11. Asphyxia encompasses a variety of conditions that involve interference with the intake of ______________ .

12. True or False: Death at a fi re scene is primarily caused by the extremely toxic gas carbon monoxide. ______________

13. The protein in red blood cells that transports oxygen is known as ______________ .

14. True or False: High levels of carbon monoxide must be pres- ent for a victim to become disoriented and lose conscious- ness. ______________

15. True or False: Carbon monoxide will continue to build up in the body after death. ______________

16. Carbon monoxide levels and the presence of soot can be used to determine whether the individual was ______________ at the time of the fi re.

151

APPLICATION AND CRITICAL THINKING

1. Rigor mortis, livor mortis, and algor mortis are all used to help determine time of death. However, each method has its limitations. For each method, describe at least one condition that would render that method unsuitable or inaccurate for determining time of death.

2. What kind of forensic expert would most likely be asked to help identify human remains in each of the following conditions?

a. A body that has been decomposing for a day or two

b. Fragmentary remains of a few arm bones and part of a jaw

c. A skeleton that is missing its skull

3. Identify a reasonable manner of death for each of the follow- ing situations:

a. A contact wound to the back of the head.

b. An elevated carboxyhemoglobin blood level in a fi re victim.

c. A fractured hyoid bone.

d. Death by overdose of a fi rst-time user of alcohol.

e. A gunshot wound to the chest from a distance of 3 feet.

f. Sudden death of a young chronic user of cocaine.

17. Victims of hangings often show signs of ______________ on the eyelids, cheeks, and forehead.

18. Petechiae are caused by the escaping of blood into the tissue as a result of ______________ bursting.

19. True or False: Petechiae are more common in hangings than strangulation deaths. ______________

20. True or False: Typically the hyoid bone and thyroid cartilage are not fractured in hanging cases. ______________

21. True or False: For gunshot victims, the cause of death can be listed as a gunshot wound. ______________

22. True or False: Because drug abuse is so common, the forensic pathologist will routinely test for the presence of drugs in nearly all investigations. ______________

23. A(n) ______________ in its broadest defi nition is simply the examination of a body after death.

24. True or False: There are two types of autopsies: a forensic/ medicolegal autopsy and a clinical/hospital autopsy. ______________

25. The autopsy consists of a(n) ______________ examination and a(n) ______________ examination.

26. The discharge from a fi rearm will produce characteristic markings on the skin known as ______________ .

27. True or False: X-ray examinations are most commonly per- formed in gunshot wound cases and stab wound cases. ______________

28. Pulmonary ______________ , or fl uid accumulation in the lungs, is frequently found in victims of chronic cocaine and amphetamine abuse.

29. True or False: The liver can contain partially digested or dissolved pills. ______________

30. True or False: The ideal location to take a blood sample is from the heart. ______________

31. ______________ is the redistribution of drugs after death.

32. True or False: General testing for poisons is not a routine procedure carried out by the pathologist. ______________

33. A body that displays a cherry-red discoloration often leads a pathologist to suspect poisoning by ______________ .

34. True or False: A pathologist can often give an exact time of death. ______________

35. The process of the body’s continually decreasing in tempera- ture after death until it reaches the environmental tempera- ture is known as ______________ .

36. The process of the blood settling in parts of the body closest to the ground after death is known as ______________ .

37. True or False: Different lividity patterns on a body may indi- cate that the body was moved after death but before livor mortis had fully fi xed. ______________

38. Levels of ______________ in the ocular fl uid can help indi- cate the time of death.

39. After death, two decomposition processes take place: ______________ and ______________ .

40. The female bone structure differs from the male structure within the ______________ area because of a woman’s childbearing capabilities.

41. True or False: A defi nite identifi cation of remains cannot be made through the analysis of the decedent’s DNA profi le, fi ngerprints, or medical records. ______________

42. True or False: A site where human remains are found must be treated as a crime scene, and the site and surrounding area should be secured, searched, and carefully processed. ______________

43. The fi eld of ______________ takes advantage of the durable nature of bones over a long period of time to exam- ine and identify human skeletal remains through a multitude of individual characteristics.

44. The study of insects and their relation to a criminal investiga- tion, known as ______________ , is commonly used to esti- mate the time of death when the circumstances surrounding the crime are unknown.

45. By determining the oldest stage of fl y found on the body and taking environmental factors into consideration, entomolo- gists can approximate the ______________ interval.

46. True or False: Another method to determine PMI is by observ- ing the schedule of arrival of different insects species on the body. ______________

DEATH INVESTIGATION

152

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DESIGN SERVICES OF

S4carliSle Publishing Services

4. Creating a Forensic Anthropology Victim Profile A nearly complete human skeleton has been found. The skel- eton has the features shown in the accompanying table and

image. Approximate the gender, ancestry, age range, and height of the individual based on this information.

Cranium Size Medium Forehead Rounded, projected outward Mastoid process Absent Jaw Angle 5 110 degrees Teeth All permanent Sagittal suture Not fused Coronal suture Not fused Eye orbits Squared Nasal cavity Large, wide Incisors Smooth Pelvis Opening See figure Sacrum See figure Subpubic angle 90–100 degrees Long Bones Femur Fully fused, 44.1 cm long Clavicle Fully fused Gender ______________ Ancestry ______________ Age Range ___________ Height _______________

DeAth InVestIgAtIon

5. sequence of Insect Arrival in Forensic entomology The following images depict the sequence of events at the site of a decomposing body. Place the arrival events in order of occurrence from earliest to latest.

Courtesy Dorling Kindersley Media Library

(A), (B), (E) courtesy Dorling Kindersley Media Library; (C) Suede Chen/Shutterstock; (D) irin-k/Shutterstock; (F) Ian Thraves/Alamy

(A) (B) (C)

(D) (E) (F)

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Crime-Scene Reconstruction

From Chapter 7 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

THE ASSASSINATION OF PRESIDENT KENNEDY Ever since President John F. Kennedy was killed in 1963, questions have lingered about whether Lee Harvey Oswald was part of a conspiracy to assassinate the president or a lone assassin. The Warren Commission, the offi cial government body appointed to investigate

the shooting, concluded that Oswald acted alone. However, over the years, eyewitness ac- counts and acoustical data interpreted by some experts have been used to contend that a sec- ond shooter fi red at the president from a region in front of the limousine (the so-called “grassy knoll”).

In arriving at its conclusions, the Warren Commission reconstructed the crime as follows: From a hidden position on the sixth fl oor of the Texas School Book Depository building where he worked, Oswald fi red three shots from behind the president. Two bullets struck the president, one bullet of which missed the president’s limousine. One bullet hit the president in the back, exited through his throat, and went on to strike Texas governor John Connally, who was sitting in a jump seat in front of the president. In a sixth-fl oor room at the Texas School Book Depository, police found a rifl e with Oswald’s

palm print on it. They also found three spent cartridge cases.

In 1977, the US House of Representatives Select Committee on Assassinations requested that the bullet taken from Connally’s stretcher—along with bullet frag- ments recovered from the car and various wound areas— be examined for levels of trace elements. Investigators compared the antimony and silver content of the bullet and bullet fragments recovered after the assassination and concluded that all of the fragments probably came from two bullets.

In 2003, ABC TV broadcast the results of a ten- year 3-D computer animation study of the events of November  22, 1963. The animation graphically showed that the bullet wounds were completely consistent with Kennedy’s and Governor Connally’s positions at the time of the shooting, and that by following the bullets’ trajec- tories backward they could have originated only from a narrow region including a few windows on the sixth fl oor of the School Book Depository.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Defi ne crime-scene reconstruction . • Discuss the ways investigators maintain objectivity during

reconstruction. • Understand the processes of deductive reasoning, inductive

reasoning, and falsifi ability and how these processes are used in reconstruction.

• Describe the limitations and fallacies involved in the reconstruction of crime scenes.

• Explain the role physical evidence, testimonial evidence, and reenactments play in reconstructing the events surrounding the commission of a crime.

• Describe the utility of an event timeline in a crime-scene reconstruction.

Crime-Scene

Reconstruction

Dennis Beach/Warren Commission/Dennis Brach A/Newscom

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CRIME-SCENE RECONSTRUCTION

Fundamentals of Crime-Scene Reconstruction Previous discussions dealing with the processes of identifi cation and compari- son have stressed laboratory work routinely performed by forensic scientists. However, there is another dimension to the role that forensic scientists play during the course of a criminal investigation: participating in a team effort to reconstruct events that occurred prior to, during, and subsequent to the commission of a crime.

Reconstructing the circumstances of a crime scene entails a collaborative effort that includes experienced law enforcement personnel, medical examiners, and criminalists. All of these professionals contribute unique perspectives to develop the crime-scene reconstruction. Was more than one person involved? How was the victim killed? Were actions taken to cover up what took place? To answer these questions, all personnel involved with the investigation must pay careful attention and think logically.

Crime-scene reconstruction is the method used to develop a likely sequence of events at a crime scene by observing and evaluating physical evidence and statements made by individuals involved with the incident. The evidence may also include information obtained from reenactments. Therefore, reconstructions have the best chance of being accurate when investigators use proper documentation and collection methods for all types of evidence.

STRIVING FOR OBJECTIVITY

One of the most important features of a logical and systematic inquiry is objectivity. Objectivity is professional detachment practiced by individuals to avoid letting personal beliefs or biases affect the conclusions they reach through observations. Even trained scientists come to their jobs with some expectations or biases. These can have a negative effect on the process of reconstruction by leading to the incorrect analysis or interpretation of the information provided by the evidence. For that reason, all data and evidence must be continually reevaluated throughout the process of crime-scene recon- struction. It may also be wise to have several individuals analyze the evidence and present independent interpretations.

Investigators should approach each case free of previous theories or expectations. For example, if a victim is found dead from a gunshot wound to the temple and he is holding a gun, the investigator should not assume his death was a suicide. Surmising that the death was a suicide may cause the investigator to create a “self-fulfi lling prophecy” by considering only information that supports this theory in the reconstruction. Crime-scene reconstruction personnel should never try to prove any theory or hypothesis. Instead, they should use the processes of deductive reasoning, inductive reasoning, and falsifi ability to create a logical reconstruction of crime-scene events.

DEDUCTIVE REASONING Deductive reasoning is the process of drawing a conclusion based on known facts or premises. Using deductive reasoning allows an investigator to come to a defi nitive conclusion. For example, if an investigator fi nds a fi ngerprint from the victim on a table, then the victim defi nitely touched the table with whatever fi nger the print came from. This conclusion makes no assumptions about how, when, or why the victim touched the table, but it establishes a concrete event. Another example is locating a muddy footprint outside the door of a burglary scene. Laboratory examination shows the impression to have individual markings belonging to a sneaker owned by a suspect. Linking the footprint to a particular suspect strongly suggests the presence of the suspect’s footwear at the crime scene.

crime-scene reconstruction The method used to develop a likely sequence of events at a crime scene by the observation and evaluation of physical evidence and statements made by individuals involved with the incident.

objectivity A manner of professional detachment practiced by individuals to avoid letting personal beliefs or biases affect the conclusions reached through observations.

deductive reasoning The process of drawing a conclusion based on known facts or premises.

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CRIME-SCENE RECONSTRUCTION

This observation becomes particularly relevant in identifying the suspect as the perpetrator if it can be shown that the suspect has no prior association with the locale of the crime.

INDUCTIVE REASONING When using inductive reasoning , one attempts to draw a conclusion based on premises one does not know are correct. This pro- cess leads to a conclusion that is probable but not defi nitive. Here the danger is overgeneralization—making an observation about an event and assuming the observation is always or nearly always applicable to events of the same kind. For example, if a large amount of a victim’s blood is found at a crime scene, then the victim probably was present and injured at the crime scene. It is also possible that the victim was injured somewhere else and large amounts of her blood were transported to the scene, but this scenario is not probable. One must be careful using conclusions drawn from inductive reasoning, and never confuse them with conclusions drawn from deductive reasoning.

FALSIFIABILITY It is very easy for an investigator to locate and include evidence that supports a theory. To avoid causing a self-fulfi lling prophecy, investigators should test the falsifi ability of a theory. This means that they should try to dis- prove the theory. Those involved in reconstructing the crime scene must always be aware of all plausible alternatives that could have led to the state of any piece of evidence. They must keep an open mind to avoid narrowing their view to one or a few possibilities, potentially excluding more plausible scenarios. Once they have identifi ed all possibilities, the investigators should set about prioritizing their reconstruction theories. They may do this by examining each alternative explanation and determining how consistent it is with the physical evidence, eyewitness accounts, and general dynamics of the crime scene.

The crime-scene reconstruction typically produces the most probable conclusion. However, being mindful of plausible alternate explanations will help provide other leads if an aspect of a reconstruction theory does not appear to fi t all the facts of the case. No evidence or data should ever be excluded. A crime-scene reconstruction theory must be supported by all interpreted evidence or it cannot be accepted.

LIMITATIONS TO RECONSTRUCTION

Crime-scene investigators apply systematic reasoning to bolster their recon- structions, but certain fallacies of reasoning can undermine their conclusions. Each inquiry must be accompanied by an attitude of skepticism and knowl- edge of fallacies that can impede a search for the truth.

BIFURCATION The fallacy of bifurcation happens when investigators or at- torneys try to apply a simple “yes or no” answer to a complex question. Not all information gained from the crime scene leads to a clear-cut solution or conclusion, and asking for a simple answer to a complex question may be an attempt to cloud the truth.

GENERALIZATION Generalizing about aspects of evidence can be both helpful and harmful to an investigation. Generalizations about the shape of bloodstains can help determine the direction and approximate angle of the deposition of a droplet. This is helpful to the investigation and reconstruc- tion. However, generalizations about the kind of force that creates a pattern may send the investigation in the wrong direction. For example, fi ne droplets, called high-velocity spatter, are usually found when a victim suffers a gunshot wound. However, sometimes blunt force beatings also produce fi ne droplets that look like high-velocity spatter. If an investigator generalizes that high- velocity spatter always comes from gunshot wounds, this may divert the in- vestigation toward looking for a weapon that doesn’t exist.

inductive reasoning The process of drawing a conclusion from premises one does not know are correct.

falsifi ability The ability of a theory to be disproved by being tested against known information.

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CRIME-SCENE RECONSTRUCTION

FALSE LINKAGE False linkage occurs when an investigator assumes a link between two or more objects of evidence that starts the investigation down the wrong path. For example, suppose that investigators fi nd footwear impressions at a crime scene in a high-traffi c area of a park. The investigators may assume the impressions are linked to the perpetrator when in truth they may belong to an unrelated person who walked there earlier in the day.

The biggest limitation associated with reconstruction is that investigators can use only what is left behind to theorize what occurred in the past. The information available to make these theories is often much less than would be needed to create a full timeline of events. The reconstruction team can only strive to make optimum use of all the available evidence, witness statements, and appropriate investigative leads to defi ne what events occurred at specifi c moments and the order in which they happened. Reconstruction also relies on information from toxicology tests, DNA typing, autopsies, interrogations, and many other sources. However, the results of these tests and processes may take quite a bit of time. This means that the reconstructing team may not receive all relevant information for days, weeks, or months after the incident. It is important to remember that crime-scene reconstruction does not provide instant gratifi cation for all the effort it requires.

Quick Review • Because crime-scene reconstruction develops a likely sequence of events

at a crime scene with physical evidence, testimony, and reenactments, proper documentation and collection methods must be used for all types of evidence.

• Investigative personnel bring some expectations or biases to reconstruc- tion, and these can have a negative effect on the process. It is, therefore, very important for personnel to practice objectivity, or professional distance.

• The processes of deductive reasoning, inductive reasoning, and falsifi ability are very important to the reconstruction process, but they must be differen- tiated and used properly.

• Investigators must be aware that the fallacies of bifurcation, general- ization, and false linkage can impede a search for the truth. Avoiding these fallacies will help investigators maintain objectivity throughout the reconstruction.

Requirements for Crime-Scene Reconstruction PERSONNEL INVOLVED IN RECONSTRUCTION

Because investigators consider many types of evidence when reconstructing a crime scene, reconstruction is a team effort that involves various profession- als putting together many pieces of a puzzle. The team as a whole works to answer the typical “who, what, when, where, why, and how” of a crime scene. Often, reconstruction requires the involvement of a medical examiner and at least one criminalist. For example, an investigator might call on a trained medical examiner to determine whether a body has been moved after death by evaluating the livor distribution within the body. A criminalist or trained crime-scene investigator can also bring special skills to the reconstruction of events that occurred during the commission of a crime. For example, a crimi- nalist using a laser beam to plot the approximate trajectory of a bullet can help determine the probable position of the shooter relative to that of the victim (see Figure 1 ).

159

CRIME-SCENE RECONSTRUCTION

Other skills that a criminalist or expert may employ during a crime-scene reconstruction analysis include blood spatter analysis, determining the direc- tion of impact of projectiles penetrating glass objects, locating gunshot resi- dues deposited on victims’ clothing for the purpose of estimating the distance of a shooter from a target, and searching for primer residues deposited on the hands of a suspect shooter.

GATHERING EVIDENCE

AND DATA FROM THE CRIME SCENE

Physical evidence left behind at a crime scene plays a crucial role in reconstructing the sequence of events surrounding the crime. Although the evidence alone may not describe everything that happened, it can support or contradict accounts given by witnesses and/or suspects. Information obtained from physical evidence can also generate leads and confi rm the reconstruc- tion of a crime to a jury. The collection, documentation, and interpretation of physical evidence is the foundation of a reconstruction. Reconstruction develops a likely sequence of events by the observation and evaluation of physical evidence as well as statements made by witnesses and input from those involved with the investigation of the incident. Analysis of all available data will help to create a workable model for reconstruction.

DIRECT PHYSICAL EVIDENCE Information from direct physical evidence provides a defi nite conclusion or direction. The analysis of direct physical evi- dence employs deductive reasoning to state a fact that can be understood by everyone. For example, if a transfer bloodstain on the clothing of a homicide victim has a DNA type consistent with that of the suspect, the victim must have had contact with the suspect after the suspect was injured and began bleed- ing. However, this assumes no prior contact or relationship existed between the victim and the suspect.

CIRCUMSTANTIAL EVIDENCE Information from circumstantial evidence provides a lead but no defi nite conclusion. With the use of inductive reasoning,

FIGURE 1 A laser beam is used to determine the search area for the position of a shooter who has fi red a bullet through a window and wounded a victim. The bullet’s path is determined by lining up the victim’s bullet wound with the bullet hole in the pane of glass.

Bullet entrance wound

Search path for evidence of shooter

Laser

Mannequin

Window

Bullet hole

direct physical evidence An item of evidence from which an indisputable fact or detail of the events at the crime scene can be concluded.

circumstantial evidence An item of evidence that suggests the occurrence of one of several possible events at the crime scene.

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CRIME-SCENE RECONSTRUCTION

an investigator can identify many possible causes for the state of the evidence. For example, the presence of semen in the DNA analysis of a female victim can be consistent with either forcible rape or consensual sex. Individual hair or fi ber evidence found at the scene is considered highly circumstantial. It may suggest that an individual was present during the commission of the crime, but there are also other probable explanations for how it got there. Circum- stantial evidence, when examined in the context of a crime scene, has only a few possible explanations, and one of these may be more probable than the others.

TESTIMONIAL EVIDENCE An investigator should carefully scrutinize eyewit- ness testimony about what occurred at a crime scene. Eyewitness accounts, also called testimonial evidence , are sometimes highly subjective and heav- ily biased. Unfortunately, people lie or misinterpret the facts. Fortunately, physical evidence does not lie. Therefore, crime-scene reconstruction should include only testimonial evidence that is corroborated by aspects of physical evidence.

REENACTMENTS Some events at the crime scene lend themselves to a reenactment by live personnel, mannequins, or computer-generated models. Individuals used in live reenactments should be as close as possible in size and strength to the actual participants at the crime scene. The information gained from reenactments can show whether a theory of how an event occurred is physically possible and whether physical evidence is consistent with that  theory.

CONFIRMING CHAIN OF CUSTODY

As mentioned previously, a great deal of time may pass before all pertinent evidence and information can be gathered in order to begin reconstruction. Once all the evidence has been gathered, investigators must establish the chain of custody of items and the integrity of testimonial evidence. A missing link in the chain of custody of an item means that it was unaccounted for during a period of time. During this time, the evidence could have been tampered with, contaminated, or damaged. Evidence without a confi rmed chain of custody cannot and should not be included in reconstruction. If there is any question about the legality or authenticity of testimonial evidence, it should be excluded from reconstruction.

Quick Review • Crime-scene reconstruction is a team effort that requires the expertise of

various professionals, depending on the kind of case. • Information gathered from direct physical evidence provides a defi nite

conclusion or direction, whereas circumstantial evidence provides a lead but no defi nite conclusion for reconstructing the crime.

• Testimonial evidence from eyewitnesses is sometimes highly subjective and heavily biased and must be used in reconstruction only if it is corroborated by physical evidence.

• Reenactments of events at a crime scene can be carried out by live person- nel, mannequins, or computer-generated models.

• Evidence used in a crime-scene reconstruction must have a complete and valid chain of custody.

testimonial evidence Informational evidence gained from statements from witnesses, suspects, and others who have some knowledge of the crime scene.

reenactment The process by which investigators attempt to re-create the circumstances surrounding a particular event at the crime scene in order to observe the result and gain information.

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CRIME-SCENE RECONSTRUCTION

Assessment of Evidence and Information to Form Theories One of the pitfalls of crime-scene reconstruction is generalizing the assess- ment and processing of evidence. Different categories or types of crime-scene evidence must be studied with very specifi c techniques and considerations during the investigation. The kinds of evidence that may be found at a crime scene are highly diverse.

ASSESSMENT OF EVIDENCE

Each item of evidence should fi rst be analyzed and tested separately from all other evidence. To maintain objectivity and avoid the fallacy of false linkage, items of evidence should not be linked or grouped together during the initial phase of the investigation. Once all possible information has been recovered from each item, this information can be coupled with information about other items of evidence. It is important at this step to observe whether separate items of evidence make sense together or verify an event. For example, suppose an investigator fi nds that a trail of blood leading down the back stairs of a house stops abruptly at a patch of dirt. This might seem unusual but would make perfect sense if tire impressions were found in the dirt at the location where the trail stops. The investigator seeks to use evidence to link the crime scene, victims, suspects, and witnesses. These links provide the foundation for theo- ries about specifi c events at the crime scene. Missing links may help to suggest what further data need to be recovered from available evidence or witnesses.

Studying the pattern formed by cartridges ejected from a fi rearm provides an excellent illustration of the process and diffi culty of gaining information from a specifi c type of evidence. The location of a cartridge casing at a crime scene may suggest the position of the shooter, but the investigator must take into consideration the type of fi rearm used, the type of ammunition used, the position of the gun with respect to the shooter’s body, the height of the fi rearm from the ground, and the terrain and layout of the scene. Investigators study the effect of these conditions through reenactments that must be as authentic as possible. The reenactment should involve the same fi rearm and ammunition used in the crime. Even the amount of lubrication of the fi rearm may affect cartridge ejection characteristics. The fi ring position of the fi rearm—whether sideways, upright, or otherwise—can affect where a cartridge will fall.

As with many kinds of evidence, with cartridge case ejection, investigators must take substrate conditions into consideration. That is, the type and topography of the surface onto which the cartridge falls may affect its posi- tion. For example, a cartridge may travel farther after landing on an angled surface or a hard surface, such as concrete, than it would after landing on a level or soft surface. Cartridge cases may also contain trace evidence of dam- age if they contacted an intermediate surface before landing. A matching mark on the surface the cartridge contacted may also help to determine the shooter’s position.

The cartridge itself can provide clues about the fi rearm that ejected it. The cartridge may bear marks on the base from the breechblock, fi ring pin, and ejector mechanism of the gun. The shaft of the cartridge may show chamber- ing marks, gouge marks, and drag marks imparted by the fi ring chamber of the fi rearm. The collection of marks, their position, and any striations (i.e., fi ne grooves) within the marks will probably be unique to one fi rearm. Cartridge cases represent only one example of many types of evidentiary items that may

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CRIME-SCENE RECONSTRUCTION

be found at a crime scene. However, this example clearly demonstrates that a complex set of techniques and considerations are involved in studying each piece of evidence.

The example of cartridge case ejection patterns also raises the specter that an attempt at reconstruction can fail. That is, the movement of the shooter, the number of shooters, and the number of bullets discharged will produce multiple cartridge cases in various locations, introducing complexities into the analysis. These complexities may not be as easy to resolve as they would in a reconstruction involving a single cartridge case. When such complexities arise, some investigators fall into the trap of reading too much into evidence that may not provide resolution. The fact is, reconstruction may not be able to answer all of the questions. The complexities of the analysis may overwhelm the reconstruction team and prevent them from coming up with plausible answers.

FORMING THEORIES FOR RECONSTRUCTION

The fi nal steps of crime-scene reconstruction require the reconstruction team to bring together all the evidence and information to form plausible theories and a plausible sequence of individual events. Theories can suggest how a group of linked items was created by individual events at a crime scene.

Often the beginning and end of the sequence of events at a crime scene are obvious to the investigators. For example, a tool mark or a footwear impres- sion can mark the site of forced entry into a house, beginning the sequence of events at the crime scene. Footwear impressions or tire impressions leading away from the house may show the exit of the suspect from the crime scene and thus the end of the sequence of events. However, the sequence and timeline of the remaining events may be much more diffi cult to determine. Sometimes the evidence that signifi es the start or end of events provides clues to the miss- ing events in the middle. For example, suppose an investigator fi nds bloody footwear imprints exiting a crime scene. Logic dictates that blood was present at the crime scene, and that it somehow became deposited on the shoes of an individual who subsequently left the crime scene. These clues can provide suggestions about where the reconstruction should focus its attention.

All available information and evidence must fi t into the overall picture. When creating a crime-scene reconstruction, the team must focus on the issues at hand and use all the information that is not in dispute to create a framework in which to explore defi nitive events.

An event timeline will list each event or “moment” that occurred at a crime scene in various probable orders within a known or estimated time frame. Some reconstruction teams develop an event timeline chart (see Figure  2 ). Investigators should chart each sequence and include information on evidence to illustrate how each event could have occurred and the timeline in which they occurred. Once the various orders have been identifi ed, each sequence should be tested against the evidence.

Quick Review • In order for physical or testimonial evidence to be used in reconstruction

theories, the chain of custody of items and the integrity of testimonial evi- dence must be established.

• Individual items of evidence are fi rst analyzed and tested separate from all other evidence; items should not be linked or grouped together during the initial phase of the investigation. Once all items have been evaluated this way, they may be coupled with other items of evidence that are clearly linked.

event timeline The end product of crime-scene reconstruction that shows the possible sequence of occurrences at the crime scene and the known or estimated time period in which they took place.

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CRIME-SCENE RECONSTRUCTION

• Different categories or types of crime-scene evidence have to be studied with very specifi c techniques and considerations during the investigation. The kinds of evidence that may be found at a crime scene are highly diverse, and knowledge of techniques for processing each is needed to recover all pertinent information.

• The reconstruction team must bring together all the linked groups of evi- dence and information to form theories about how each group of linked items was created by individual events at a crime scene.

CHAPTER REVIEW

• Because crime-scene reconstruction develops a likely se- quence of events at a crime scene with physical evidence, testimony, and reenactments, proper documentation and collection methods must be used for all types of evidence.

• Investigative personnel may bring some expectations or biases to reconstruction, and these can have a negative effect on the process. It is, therefore, very important for per- sonnel to practice objectivity, or professional distance.

• The processes of deductive reasoning, inductive reasoning, and falsifi ability are very important to the reconstruction process, but they must be differentiated and used properly.

• Investigators must be aware that the fallacies of bifurcation, generalization, and false linkage can impede a search for the truth. Avoiding these fallacies will help investigators main- tain objectivity throughout the reconstruction.

• Crime-scene reconstruction is a team effort that requires the  expertise of various professionals, depending on the kind of case.

• Information gathered from direct physical evidence provides a defi nite conclusion or direction, whereas circumstantial evidence provides a lead but no defi nite conclusion for reconstructing the crime.

• Testimonial evidence from eyewitnesses is sometimes highly subjective and heavily biased and must be used in recon- struction only if it is corroborated by physical evidence.

• Reenactments of events at a crime scene can be carried out by live personnel, mannequins, or computer-generated models.

• Evidence used in a crime-scene reconstruction must have a complete and valid chain of custody.

• In order for physical or testimonial evidence to be used in reconstruction theories, the chain of custody of items and the integrity of testimonial evidence must be established.

• Individual items of evidence are fi rst analyzed and tested separate from all other evidence; items should not be linked or grouped together during the initial phase of the investi- gation. Once all items have been evaluated this way, they may be coupled with other items of evidence that are clearly linked.

• Different categories or types of crime-scene evidence have to be studied with very specifi c techniques and considerations during the investigation. The kinds of evidence that may be found at a crime scene are highly diverse, and knowledge of techniques for processing each is needed to recover all pertinent information.

• The reconstruction team must bring together all the linked groups of evidence and information to form theories about how each group of linked items was created by individual events at a crime scene.

KEY TERMS

circumstantial evidence

crime-scene reconstruction

deductive reasoning

direct physical evidence

event timeline

falsifi ability

inductive reasoning

objectivity

reenactment

testimonial evidence

165

APPLICATION AND CRITICAL THINKING

1. Which logical fallacy is described in each of the following situations?

a) An investigator fi nds a body wrapped in a bloody sheet and assumes that all the blood came from the victim.

b) An offi cer investigating a hit-and-run accident spots a car with a dented bumper near the scene and assumes it was involved.

c) The district attorney asks an investigator whether highly suggestive circumstantial evidence leads to a particular conclusion.

2. While investigating a murder scene, police gather evidence that includes a dead body riddled with stab wounds,

fi ngerprints on a bloody knife found near the body, and a ticket stub from a theater several miles away from the scene. Investigators determine that the knife belonged to the victim, but matched the prints on the knife to an acquain- tance of the victim. When questioned, the acquaintance claims he was at the movies at the time of the murder—the same movie shown on the stub found at the scene. What direct physical evidence connects the acquaintance to the crime scene? What circumstantial evidence connects him to the scene? What can you conclude about the acquain- tance’s involvement solely from direct physical evidence and deductive reasoning? What might you conclude considering circumstantial evidence and inductive reasoning as well?

REVIEW QUESTIONS

1. ______________ is the method used to develop a likely sequence of events at a crime scene by the observation and evaluation of physical evidence and statements made by individuals involved with the incident.

2. Reconstructing the circumstances of a crime scene is a team effort that may include the help of law enforcement person- nel, medical examiners, and ______________ .

3. To avoid letting personal beliefs or biases affect the conclu- sions reached through observations, crime-scene reconstruc- tion teams must practice ______________ .

4. True or False: Expectations or biases can have a positive effect on the process of reconstruction by leading to correct analysis or interpretation of the information provided by the evidence. ______________

5. True or False: Members of the crime-scene reconstruction team should design the examination and theory formation process to prove a theory or hypothesis that they believe to be true. ______________

6. ______________ reasoning is being used when a given fact or fi nding leads to a conclusion that is probable but not defi nitive. ______________ reasoning is being used when a given fact or fi nding leads to a defi nitive conclusion.

7. Inductive reasoning is used to analyze ______________ that provides a lead but no defi nite conclusion.

8. Another way to avoid bias is to test the ______________ of all theories of how a crime occurred and all plausible alterna- tives against the evidence.

9. The inherent fallacy of ______________ exists when inves- tigators or attorneys try to apply a simple “yes or no” answer to a complex question.

10. True or False: Generalizing about aspects of evidence is always helpful to an investigation. ______________

11. When a link is prematurely assumed between two or more objects of evidence, this is the fallacy of ______________ .

12. True or False: The biggest limitation to crime-scene recon- struction is the fact that what is left behind at a crime scene is often much less than is needed to create a full timeline of events that occurred in the past. ______________

13. ______________ left behind at the crime scene is helpful in reconstruction to support or contradict accounts given by witnesses and/or suspects.

14. The analysis of ______________ employs deductive rea- soning and provides a defi nite conclusion or direction.

15. Eyewitness accounts, called ______________ , are some- times highly subjective and heavily biased because people may lie or misinterpret the facts.

16. The re-creation of events at a crime scene, called a ______________ , may be performed by live personnel, mannequins, or computer-generated models.

17. For an item of physical evidence to be used in a reconstruc- tion, it must have a confi rmed and intact ______________ .

18. True or False: Each item of evidence should fi rst be analyzed and tested separate from all other evidence to avoid false linkage of evidence. ______________

19. True or False: The kinds of evidence that may be found at a crime scene are few, and similar categories or types of crime- scene evidence have to be studied with similar techniques and considerations. ______________

20. Once all evidence has been evaluated, the reconstruction team must bring together all the evidence and information to form plausible ______________ .

21. True or False: The beginning and end of the sequence of events at a crime scene are usually obvious to the investi- gators and may suggest what events occurred in between. ______________

22. A(n) ______________ created for the reconstruction defi nes each event that occurred at a crime scene in various probable orders within a known or estimated time frame.

CRIME-SCENE RECONSTRUCTION

166

JAMES EARL RAY: CONSPIRATOR OR LONE GUNMAN? Since his arrest in 1968 for the assassination of Dr. Martin Luther King Jr., endless speculation has swirled around the motives and connections of James Earl Ray. Ray was a career criminal who was serving time for armed robbery when he escaped from the Missouri State Prison

almost one year before the assassination. On April 3, 1968, Ray arrived in Memphis, Tennessee. The next day he rented a room at Bessie Brewer’s Rooming House, across the street from the Lorraine Motel, where Dr. King was staying.

At 6:00 p.m., Dr. King left his second- story motel room and stepped onto the balcony. As King turned toward his room, a shot rang out, striking the civil rights activist. Nothing could be done to revive him, and Dr. King was pronounced dead at 7:05 p.m. The assailant ran on foot from Bessie Brewer’s, stopping to leave a blanket-covered package in front of a nearby building, and then drove off in a white Mustang. The package contained a high-powered rifl e equipped with a scope, a radio, some clothes, a pair of binoculars, a couple of beer cans, and a receipt for the

binoculars. Almost a week after the shooting, the white Mustang was found abandoned in Atlanta, Georgia.

Fingerprints later identifi ed as James Earl Ray’s were found in the Mustang, on the rifl e, on the binoculars, and on a beer can. In 1969, Ray entered a guilty plea in return for a sentence of ninety-nine years. Although a variety of conspiracy theories surround this crime, it is an indisput- able fact that a fi ngerprint on the rifl e that killed Martin Luther King Jr. was from the hands of James Earl Ray.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Identify the common ridge characteristics of a fi ngerprint. • List the three major fi ngerprint patterns and their respective

subclasses. • Distinguish visible, plastic, and latent fi ngerprints. • Describe the concept of an automated fi ngerprint

identifi cation system (AFIS). • List the techniques for developing latent fi ngerprints

on porous and nonporous objects. • Describe the proper procedures for preserving a developed

latent fi ngerprint.

Fingerprints

Time & Life Pictures/Getty Images

From Chapter 8 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

FINGERPRINTS

History of Fingerprinting Since the beginnings of criminal investigation, police have sought an infallible means of human identifi cation. The fi rst systematic attempt at personal identifi cation was devised and introduced by a French police expert, Alphonse Bertillon, in 1883. The Bertillon system relied on a detailed description ( portrait parlé ) of the subject, combined with full-length and profi le photographs and a system of precise body measurements known as anthropometry .

The use of anthropometry as a method of identifi cation rested on the premise that the dimensions of the human bone system remain fi xed from age 20 until death. Skeleton sizes were thought to be so extremely diverse that no two individuals could have exactly the same measurements. Bertillon rec- ommended the routine taking of eleven measurements of the human anatomy, including height, reach, width of head, and length of the left foot.

For two decades, this system was considered the most accurate method of identifi cation. But in the early years of the twentieth century, police began to appreciate and accept a system of identifi cation based on the classifi cation of fi nger ridge patterns known as fi ngerprints . Today, the fi ngerprint is the pillar of modern criminal identifi cation.

EARLY USE OF FINGERPRINTS

In China fi ngerprints were used as far back as three thousand years ago to sign legal documents. Whether this practice was performed as a ceremonial custom or as a means of proving personal identity remains a point of conjecture; the answer is lost to history. The examples of fi ngerprinting in ancient history are  ambiguous, and the few prints that remain did not in fact contribute to the development of fi ngerprinting techniques as we know them today.

Several years before Bertillon began work on his system, William Herschel, an English civil servant stationed in India, started requiring Indian citizens to sign contracts with the imprint of their right hand, which was pressed against a stamp pad for the purpose. The motives for Herschel’s requirement remain unclear: He may have envisioned fi ngerprinting as a means of personal iden- tifi cation, or he may have been adapting for his purposes the Hindu custom that a trace of bodily contact is more binding than a signature on a contract. In any case, he did not publish anything about his activities until after Henry Fauld, a Scottish physician working in a hospital in Japan, published his own views on the potential application of fi ngerprinting to personal identifi cation.

In 1880, Fauld suggested that skin ridge patterns could be important for the identifi cation of criminals. He told about a thief who left his fi ngerprint on a whitewashed wall, and how in comparing these prints with those of a suspect, he found that they were quite different. A few days later, another suspect was found whose fi ngerprints compared with those on the wall. When confronted with this evidence, the individual confessed to the crime.

Fauld was convinced that fi ngerprints furnished infallible proof of identifi cation. He even offered to set up, at his own expense, a fi ngerprint bureau at Scotland Yard to test the practicality of the method. But his offer was rejected in favor of the Bertillon system. This decision was reversed less than two decades later.

EARLY CLASSIFICATION OF FINGERPRINTS

The extensive research into fi ngerprinting conducted by another Englishman, Francis Galton, fi nally made police agencies aware of its potential application. In 1892, Galton published his classic textbook Finger Prints, the fi rst book of

portrait parlé A verbal description of a perpetrator’s physical characteristics and dress provided by an eyewitness.

anthropometry A system of identifi cation of individuals by measurement of parts of the body, developed by Alphonse Bertillon.

168

its kind on the subject. In Finger Prints , Galton discussed the anatomy of fi n- gerprints and suggested methods for recording them. He also proposed as- signing fi ngerprints one of three pattern types: loops, arches, or whorls. Most important, the book demonstrated that no two prints are identical and that an individual’s prints remain unchanged from year to year. At Galton’s insis- tence, the British government adopted fi ngerprinting as a supplement to the Bertillon system.

The next step in the development of fi ngerprint technology was the creation of classifi cation systems capable of fi ling thousands of prints in a logi- cal and searchable sequence. Dr. Juan Vucetich, an Argentinian police offi cer fascinated by Galton’s work, devised a workable concept in 1891. His classi- fi cation system has been refi ned over the years and is still widely used today in most Spanish-speaking countries. In 1897, another classifi cation system was proposed by an Englishman, Sir Edward Richard Henry. Four years later, Henry’s system was adopted by Scotland Yard. Today, most English-speaking countries, including the United States, use some version of Henry’s classifi ca- tion system to fi le fi ngerprints.

ADOPTION OF FINGERPRINTING

Early in the twentieth century, Bertillon’s measurement system began to fall into disfavor. Its results were highly susceptible to error, particularly when the measurements were taken by people who were not thoroughly trained. The method was dealt its most severe and notable setback in 1903 when a convict named Will West arrived at Fort Leavenworth prison. Startlingly, a routine check of the prison fi les revealed that a William West, already in the prison, could not be distinguished from the new prisoner by body measurements or even by photographs. In fact, the two men looked just like twins, and their measurements were practically the same. Subsequently, fi ngerprints of the prisoners clearly distinguished them.

In the United States, the fi rst systematic and offi cial use of fi ngerprints for personal identifi cation was adopted by the New York City Civil Service Commission in 1901. The method was used for certifying all civil service applications. Several US police offi cials received instruction in fi ngerprint identifi cation from representatives of Scotland Yard at the 1904 World’s Fair in St. Louis. After the fair and the Will West incident, fi ngerprinting began to be used in earnest in all major cities of the United States.

In 1924, the fi ngerprint records of the Bureau of Investigation and Leavenworth were merged to form the nucleus of the identifi cation records of the new Federal Bureau of Investigation. The FBI has the largest collection of fi ngerprints in the world. By the beginning of World War I, England and practically all of Europe had also adopted fi ngerprinting as their primary method of identifying criminals.

Fundamental Principles of Fingerprints Since Galton’s time, and as a result of his efforts, fi ngerprints have become an integral part of policing and forensic science. The principal reason for this is that fi ngerprints constitute a unique and unchanging means of personal identifi cation. In fact, fi ngerprint analysts have formulated three basic principles of fi ngerprints that encompass these notions of their uniqueness, stability, and appropriateness as a means of identifi cation.

FINGERPRINTS

169

FINGERPRINTS

FIGURE 1 Fingerprint ridge characteristics. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

FIRST PRINCIPLE: A FINGERPRINT

IS AN INDIVIDUAL CHARACTERISTIC;

NO TWO FINGERS HAVE YET BEEN

FOUND TO POSSESS IDENTICAL

RIDGE CHARACTERISTICS

The acceptance of fi ngerprint evidence by the courts has always been predicated on the assumption that no two individuals have identical fi nger- prints. Early fi ngerprint experts consistently referred to Galton’s calculation, showing the possible existence of 64 billion different fi ngerprints, to support this contention. Later, researchers questioned the validity of Galton’s fi gures and attempted to devise mathematical models to better approximate this value. However, no matter what mathematical model one refers to, the conclusions are always the same: The probability for the existence of two identical fi nger- print patterns in the world’s population is extremely small.

Not only is this principle supported by theoretical calculations, but just as important, it is verifi ed by the millions of individuals who have had their prints classifi ed during the past 110 years—no two have ever been found to be iden- tical. The FBI has nearly 50 million fi ngerprint records in its computer data- base and has yet to fi nd an identical image belonging to two different people.

The individuality of a fi ngerprint is not determined by its general shape or pattern but by a careful study of its ridge characteristics (also known as mi- nutiae ). The identity, number, and relative location of characteristics such as those illustrated in Figure 1 impart individuality to a fi ngerprint. If two prints are to match, they must reveal characteristics that not only are identical but also have the same relative location to one another in the print. In a judicial proceeding, a point-by-point comparison must be demonstrated by an expert, using charts similar to the one shown in Figure 2 , in order to prove the iden- tity of an individual.

An expert can easily compare the characteristics of two complete fi nger- prints; the average fi ngerprint has as many as 150 individual ridge character- istics. However, most prints recovered at crime scenes are partial impressions, showing only a segment of the entire print. Under these circumstances, the

ridge characteristics (minutiae) Ridge endings, bifurcations, enclosures, and other ridge details that must match in two fi ngerprints to establish their common origin.

Ridge

Endings

Bifurcation Ridge Ending

Enclosure

Ridge Island (Ridge Dot)

Bifurcation

170

FINGERPRINTS

expert can compare only a small number of ridge characteristics from the re- covered print to a known recorded print.

For years, experts have debated how many ridge comparisons are neces- sary to identify two fi ngerprints as the same. Numbers that range from eight to sixteen have been suggested as being suffi cient to meet the criteria of in- dividuality. However, the diffi culty in establishing such a minimum is that no comprehensive statistical study has ever determined the frequency of occur- rence of different ridge characteristics and their relative locations. Until such a study is undertaken and completed, no meaningful guidelines can be estab- lished for defi ning the uniqueness of a fi ngerprint.

In 1973, after a three-year study of this question, the International Associa- tion for Identifi cation concluded that “no valid basis exists for requiring a prede- termined minimum number of friction ridge characters which must be present in two impressions in order to establish positive identifi cation.” Hence, the fi nal determination must be based on the experience and knowledge of the expert, with the understanding that others may profess honest differences of opinion on the uniqueness of a fi ngerprint when the question of minimal number of ridge characteristics is involved. In 1995, members of the international fi nger- print community at a conference in Israel issued the Ne’urim Declaration, which supported the 1973 International Association for Identifi cation resolution.

SECOND PRINCIPLE: A FINGERPRINT

REMAINS UNCHANGED DURING

AN INDIVIDUAL’S LIFETIME

Fingerprints are a reproduction of friction skin ridges found on the palm side of the fi ngers and thumbs. Similar friction skin can also be found on the sur- face of the palms and soles of the feet. Apparently, these skin surfaces have

FIGURE 2 A fi ngerprint exhibit illustrating the matching ridge characteristics between the crime-scene print and an inked impression of one of the suspect’s fi ngers.

171

FINGERPRINTS

been designed by nature to provide our bodies with a fi rmer grasp and a resistance to slipping. A visual inspection of friction skin reveals a series of lines corresponding to hills (ridges) and valleys (grooves). The shape and form of the skin ridges are what one sees as the black lines of an inked fi ngerprint impression.

Actually, skin is composed of layers of cells. Those nearest the surface make up the outer portion of the skin known as the epidermis, and the inner skin is known as the dermis . A cross-section of skin (see Figure 3 ) reveals a boundary of cells separating the epidermis and dermis. The shape of this boundary, made up of dermal papillae , determines the form and pattern of the ridges on the surface of the skin. Once the dermal papillae develop in the human fetus, the ridge patterns remain unchanged throughout life, except for enlarging during growth.

Each skin ridge is populated by a single row of pores that are the openings for ducts leading from the sweat glands. Through these pores, perspiration is discharged and deposited on the surface of the skin. Once the fi nger touches a surface, perspiration, along with oils that may have been picked up by touch- ing the hairy portions of the body, is transferred onto that surface, thereby leaving an impression of the fi nger’s ridge pattern (i.e., a fi ngerprint). Prints deposited in this manner are invisible to the eye and are commonly referred to as latent fi ngerprints .

Although it is impossible to change one’s fi ngerprints, some criminals have tried to obscure them. If an injury reaches deeply enough into the skin and damages the dermal papillae, a permanent scar forms. However, for this to happen, such a wound would have to penetrate 1 to 2 millimeters beneath the skin’s surface. Indeed, efforts at intentionally scarring the skin can only be self-defeating, for it is totally impossible to obliterate all of the ridge charac- teristics on the hand, and the presence of permanent scars merely provides new characteristics for identifi cation.

Perhaps the most publicized attempt at obliterating fi ngerprints was that of the notorious gangster John Dillinger, who tried to destroy his own fi nger- prints by applying a corrosive acid to them. Prints taken at the morgue after

latent fi ngerprint A fi ngerprint made by the deposit of oils and/or perspiration; it is invisible to the naked eye.

Ridge island

Sweat pores

Epidermis

Papillae

Dermis

Duct of sweat gland

Sweat gland

Nerves of touch

FIGURE 3 Cross-section of human skin.

172

FINGERPRINTS

he was shot to death, when compared to fi ngerprints recorded at the time of a previous arrest, proved that his efforts had been fruitless (see Figure 4 ).

THIRD PRINCIPLE: FINGERPRINTS HAVE

GENERAL RIDGE PATTERNS THAT PERMIT

THEM TO BE CLASSIFIED SYSTEMATICALLY

All fi ngerprints are divided into three classes on the basis of their general pattern: loops , whorls , and arches . Sixty to 65 percent of the population have loops, 30 to 35 percent have whorls, and about 5 percent have arches. These three classes form the basis for all ten-fi nger classifi cation systems presently in use.

A loop must have one or more ridges entering from one side of the print, recurving, and exiting from the same side. If the loop opens toward the little fi nger, it is called an ulnar loop; if it opens toward the thumb, it is a radial loop . The pattern area of the loop is surrounded by two diverging ridges known as type lines . The ridge point at or nearest the type-line divergence and located at or directly in front of the point of divergence is known as the delta . To many, a fi ngerprint delta resembles the silt formation that builds up as a river fl ows into the entrance of a lake—hence the analogy to the geological formation known as a delta. All loops must have one delta. The core, as the name suggests, is the approximate center of the pattern. A typical loop pattern is illustrated in Figure 5 .

Whorls are actually divided into four distinct groups, as shown in Figure  8- 6 : plain, central pocket loop, double loop, and accidental. All whorl patterns must have type lines and at least two deltas. A plain whorl and a central pocket loop have at least one ridge that makes a complete circuit. This ridge may be in the form of a spiral, oval, or any variant of a circle. If an imagi- nary line drawn between the two deltas contained within these two patterns touches any one of the spiral ridges, the pattern is a plain whorl. If no such ridge is touched, the pattern is a central pocket loop.

As the name implies, the double loop is made up of two loops combined in one fi ngerprint. Any whorl classifi ed as an accidental either contains two or more patterns (not including the plain arch) or is a pattern not covered by other categories. Hence, an accidental may consist of a combination of a loop and a plain whorl or a loop and a tented arch.

FIGURE 4 The right index fi nger impression of John Dillinger, before scarifi cation on the left and afterward on the right. Comparison is proved by the fourteen matching ridge characteristics. Courtesy Institute of Applied Science, Youngsville, NC

loop A class of fi ngerprints characterized by ridge lines that enter from one side of the pattern and curve around to exit from the same side of the pattern.

whorl A class of fi ngerprints that includes ridge patterns that are generally rounded or circular and have two deltas.

arch A class of fi ngerprints characterized by ridge lines that enter the print from one side and exit the other side.

173

FINGERPRINTS

Arches, the least common of the three general patterns, are subdivided into two dis- tinct groups: plain arches and tented arches, as shown in Figure  7 . The plain arch is the sim- plest of all fi ngerprint patterns; it is formed by ridges entering from one side of the print and exiting on the opposite side. Generally, these ridges tend to rise in the center of the print, forming a wavelike pattern. The tented arch is similar to the plain arch except that instead of rising smoothly at the center, there is a sharp upthrust or spike, or the ridges meet at an angle that is less than 90 degrees. 1 Arches do not have type lines, deltas, or cores.

THE ACE-V PROCESS

ACE-V is an acronym for the four-step process— analysis, comparison, evaluation, and verifi cation —used to identify and individualize a fi ngerprint. The fi rst step requires the examiner to identify any distortions associated with the friction ridges, as well as any external factors, such as surface or deposition factors or processing techniques, that may impinge on the print’s appearance.

The comparison step requires the examiner to compare the questioned print to the known print at three levels. Level 1 looks at the general ridge fl ow and pattern confi guration. Level 2 includes locating and comparing ridge characteristics, or minutiae. Level 2 details can individualize a print. Level 3 includes the examination and location of ridge pores, breaks, creases, scars, and other permanent minutiae.

The evaluation stage requires the examination of the questioned and known prints in their totality. The fi nal result of this stage is either individual- ization, elimination, or an inconclusive determination.

FIGURE 5 Loop pattern.

Type line

Delta

Type line

Core

Plain whorl Central pocket loop

Double loop Accidental

FIGURE 6 Whorl patterns.

Plain Tented

FIGURE 7 Arch patterns.

174

FINGERPRINTS

The fi nal step in the process involves verifi cation of the examiner’s result. It requires an independent examination of the questioned and known prints by a second examiner. Ultimately, a consensus between the two examiners must be arrived at before a fi nal conclusion is drawn.

Quick Review • Fingerprints are a reproduction of friction skin ridges found on the palm

side of the fi ngers and thumbs. • The basic principles underlying the use of fi ngerprints in criminal inves-

tigations are as follows: (1) A fi ngerprint is an individual characteristic because no two fi ngers have yet been found to possess identical ridge characteristics, (2) a fi ngerprint remains unchanged during an individual’s lifetime, and (3) fi ngerprints have general ridge patterns that permit them to be systematically classifi ed.

• All fi ngerprints are divided into three classes on the basis of their general pattern: loops, whorls, and arches.

• The individuality of a fi ngerprint is determined not by its general shape or pattern but by a careful study of its ridge characteristics. The expert must demonstrate a point-by-point comparison in order to prove the identity of an individual.

• A four step process known as ACE-V (analysis, comparison, evaluation, and verifi cation) is used to identify and individualize a fi ngerprint.

• The fi nal step in the process involves verifi cation of the examiner’s conclu- sion by a second examiner.

• When a fi nger touches a surface, perspiration and oils are transferred onto that surface, leaving a fi ngerprint. Prints deposited in this manner are invisible to the eye and are commonly referred to as latent or invisible fi ngerprints.

Classifi cation of Fingerprints The original Henry system, as adopted by Scotland Yard in 1901, converted ridge patterns on all ten fi ngers into a series of letters and numbers arranged in the form of a fraction. However, the system as it was originally designed could accommodate fi les of up to only 100,000 sets of prints. Thus, as collec- tions grew in size, it became necessary to expand the capacity of the clas- sifi cation system. In the United States, the FBI, faced with the problem of fi ling ever-increasing numbers of prints, expanded its classifi cation capacity by modifying the original Henry system and adding additional extensions. These modifi cations are collectively known as the FBI system and are used by most agencies in the United States today. Although we will not discuss all of the divisions of the FBI system, a description of just one part—the primary classifi cation—will provide an interesting insight into the process of fi nger- print classifi cation.

The primary classifi cation is part of the original Henry system and provides the fi rst classifi cation step in the FBI system. Using this classifi cation alone, all of the fi ngerprint cards in the world could be divided into 1,024 groups. The fi rst step in obtaining the primary classifi cation is to pair up fi ngers, placing one fi nger in the numerator of a fraction, the other in the denominator. The fi ngers are paired in the following sequence:

R. Index

R. Thumb

R. Ring

R. Middle

L. Thumb R. Little

L. Middle L. Index

L. Little L. Ring

175

FINGERPRINTS

The presence or absence of the whorl pattern is the basis for the determi- nation of the primary classifi cation. If a whorl pattern is found on any fi nger of the fi rst pair, it is assigned a value of 16; on the second pair, a value of 8; on the third pair, a value of 4; on the fourth pair, a value of 2; and on the last pair, a value of 1. Any fi nger with an arch or loop pattern is assigned a value of 0. Approximately 25 percent of the population falls into the 1/1 category; that is, all their fi ngers have either loops or arches.

After values for all ten fi ngers are obtained in this manner, they are totaled, and 1 is added to both the numerator and denominator. The fraction thus obtained is the primary classifi cation. For example, if the right index and right middle fi ngers are whorls and all the others are loops, the primary classifi ca- tion is

16 1 0 1 0 1 0 1 0 1 1 0 1 8 1 0 1 0 1 0 1 1

5 17 9

A fi ngerprint classifi cation system cannot in itself unequivocally identify an individual; it merely provides the fi ngerprint examiner with a number of candidates, all of whom have a set of prints in the system’s fi le. The identifi ca- tion must always be made by a fi nal visual comparison of the ridge charac- teristics of the suspect print and the fi le print; only these features can impart individuality to a fi ngerprint. Although ridge patterns impart class character- istics to the print, the type and position of ridge characteristics give the print individual character.

Quick Review • The primary classifi cation is the fi rst step in classifying fi ngerprints under

the FBI system. The presence or absence of the whorl pattern is the basis for the determination of the primary classifi cation.

Automated Fingerprint Identifi cation Systems The Henry system and its subclassifi cations have proved to be a cumbersome system for storing, retrieving, and searching for fi ngerprints, particularly as fi ngerprint collections grow in size. Nevertheless, until the emergence of fi ngerprint computer technology, this manual approach was the only viable method for maintaining fi ngerprint collections. Since 1970, technological advances have made it possible to classify and retrieve fi ngerprints by com- puter. Automated fi ngerprint identifi cation systems (AFISs) have proliferated throughout the law enforcement community.

In 1999, the FBI initiated full operation of the Integrated Automated Fingerprint Identifi cation System (IAFIS), the largest AFIS in the United States, which links state AFIS computers with the FBI database. This system contains nearly 68 million fi ngerprint records. However, an AFIS can come in all sizes ranging from the FBI’s IAFIS to independent systems operated by cities, counties, and other agencies of local government (see Figure 8 ). Unfortunately, these local systems often cannot be linked to the state’s AFIS system because of differences in software confi gurations.

HOW AFIS WORKS

The heart of AFIS technology is the ability of a computer to scan and digitally encode fi ngerprints so they can be subjected to high-speed computer processing. The AFIS uses automatic scanning devices that convert the image

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FINGERPRINTS

of a fi ngerprint into digital minutiae that contain data about points of termination (i.e., ridge endings) and the branching of ridges into two ridges (i.e., bifurcations). The relative position and orientation of the minutiae are also recorded, allowing the computer to store each fi nger- print in the form of a digitally recorded geometric pattern.

The computer’s search algorithm determines the degree of correla- tion between the location and relationship of the minutiae in the search print and those in the fi le prints. In this manner, a computer can make thousands of fi ngerprint comparisons in a second. For example, a set of ten fi ngerprints can be searched against a fi le of 500,000 ten-fi nger prints (i.e., ten-prints ) in about eight-tenths of a second. During the search for a match, the computer uses a scoring system that assigns prints to each of the criteria set by an operator. When the search is complete, the computer produces a list of fi le prints that have the clos- est correlation to the search prints. All of the selected prints are then examined by a fi ngerprint expert, who makes the fi nal verifi cation of the print’s identity. Thus, the AFIS makes no fi nal conclusions about the identity of a fi ngerprint; this function is left to the eyes of a trained examiner.

The speed and accuracy of ten-print processing by AFIS systems have made it possible to search a single latent crime-scene fi ngerprint against an entire fi le’s print collection. Before AFIS, police were usually restricted to comparing crime-scene fi ngerprints against those of known suspects. The impact of the AFIS on no-suspect cases has been dramatic. In its fi rst year of operation, San Francisco’s AFIS computer conducted 5,514  latent fi ngerprint searches and achieved 1,001 identifi cations—a hit rate of 18 percent. Contrast this with the previous year’s success rate of 8 percent for manual latent-print searches.

Using a single system, an AFIS computer automatically fi lters out imperfections in a latent print, enhances its image, and creates a graphic representation of the fi ngerprint’s ridge endings and bifurcations and their directions. The computer then searches fi le prints for a match. The image of the latent print and a matching fi le print are then displayed side by side on a high-resolution video monitor, as shown in Figure 9 . The matching latent and fi le prints are then verifi ed and charted by a fi ngerprint examiner at a video workstation.

The stereotypical booking offi cer rolling inked fi ngers onto a standard ten-print card for ultimate transmission to a database has, for the most part, been replaced with digital-capture devices ( Live Scan ) that eliminate ink and paper (see Figure 10 ). The Live Scan captures an image of each fi n- ger and the palms as they are lightly pressed against a glass plate. Within minutes the booking agency can enter the fi ngerprint record into the AFIS database and then search the database for previous records of the same individual.

CONSIDERATIONS WITH AFIS

AFIS has fundamentally changed the way criminal investigators operate, allowing them to spend less time developing suspect lists and more time investigating the suspects located by the computer. However, investigators must be cautioned against overreliance on a computer. Sometimes a latent print does not generate a hit because of the poor quality of the fi le print. To avoid potential problems, investigators must still fi ngerprint all known suspects in a case and then manually search these prints against the crime- scene prints.

FIGURE 8 An AFIS system designed for use by local law enforcement agencies. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

Live Scan An inkless device that captures digital images of fi ngerprints and palm prints and electronically transmits them to an AFIS.

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FINGERPRINTS

AFIS computers are available from several suppliers. Each system scans fi ngerprint images and detects and records in- formation about minutiae (e.g.,  ridge endings and bifurca- tions); however, they do not all incorporate the same features, coordinate systems, or units of measure to record fi ngerprint information. These software incompatibilities often mean that, although state systems can communicate with the FBI’s IAFIS, they do not communicate with each other directly. Likewise, local and state systems frequently cannot share information with each other. Many of these technical problems will be re- solved as more agencies follow transmission standards devel- oped by the National Institute of Standards and Technology and the FBI.

Quick Review • The fi ngerprint database known as AFIS converts an im-

age of a fi ngerprint into digital minutiae that contain data showing ridges at their points of termination (i.e., ridge endings) and of branching into two ridges (i.e., bifurca- tions).

• AFIS makes no fi nal decisions on the identifi cation of a fi n- gerprint, instead leaving this function to a trained exam- iner.

• Live Scan is an inkless device that captures digital images of fi ngerprints and palm prints and electronically trans- mits them to an AFIS.

FIGURE 9 A side-by-side comparison of a latent print against a fi le fi ngerprint is conducted in seconds, and their similarity rating (SIM) is displayed on the upper-left portion of the screen. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

FIGURE 10 Live Scan technology enables law en- forcement personnel to print and compare a subject’s fi ngerprints rapidly, without inking the fi ngerprints. MorphoTrak, Inc.

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FINGERPRINTS

FIGURE 11 A Refl ected Ultraviolet Imaging System allows an investigator to directly view surfaces for the presence of untreated latent fi ngerprints. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www .sirchie.com

visible print A fi ngerprint made when the fi nger deposits a visible material such as ink, dirt, or blood onto a surface.

plastic print A fi ngerprint impressed in a soft surface.

Methods of Detecting Fingerprints Through common usage, the term latent fi ngerprint has come to be associated with any fi ngerprint discovered at a crime scene. Sometimes, however, prints found at the scene of a crime are quite visible to the eye, and the word latent is a misnomer.

Actually, there are three kinds of crime-scene prints. Visible prints are made by fi ngers touching a surface after the ridges have been in contact with a colored material such as blood, paint, grease, or ink; plastic prints are ridge impressions left on a soft material such as putty, wax, soap, or dust; and latent or invisible prints are impressions caused by the transfer of body perspiration or oils from fi nger ridges to the surface of an object.

LOCATING FINGERPRINTS

Locating visible or plastic prints at the crime scene normally presents little problem to the investigator because these prints are usually distinct and visible to the eye. Obviously, locating latent or invisible prints is much more diffi cult and requires the use of techniques that make the print visible. The investigator can choose from several methods for visualizing a latent print, and his or her choice depends on the type of surface being examined.

Hard and nonabsorbent surfaces (such as glass, mirror, tile, and painted wood) require different development procedures than do surfaces that are soft and porous (such as paper, cardboard, and cloth). Prints on the former sur- faces are developed preferably by the application of a powder or by treatment with Super Glue, whereas prints on the latter generally require treatment with one or more chemicals.

Sometimes the most diffi cult aspect of fi ngerprint examination is the lo- cation of prints. Recent advances in fi ngerprint technology have led to the development of an ultraviolet image converter for the purpose of detecting la- tent fi ngerprints. This device, called the Refl ected Ultraviolet Imaging System (RUVIS), can locate prints on most nonabsorbent surfaces without the aid of chemical or powder treatments (see Figure 11 ).

RUVIS detects the print in its natural state by aiming UV light at the sur- face suspected of containing prints. When the UV light strikes a fi ngerprint, the light is refl ected back to the viewer, differentiating the print from its back- ground surface. The transmitted UV light is then converted into visible light by

179

FINGERPRINTS

an image intensifi er. Once the print is located in this manner, the crime-scene investigator can develop it in the most appropriate fashion (see Figure 12 ).

DEVELOPING LATENT PRINTS

Several techniques are available to the criminalist for developing latent prints on a variety of surfaces. These range from chemical methods such as using powders and iodine fuming to the use of laser light.

FINGERPRINT POWDERS Fingerprint powders are commercially available in a variety of compositions and colors. These powders, when applied lightly to a nonabsorbent surface with a camel’s-hair or fi berglass brush, readily adhere to perspiration residues and/or deposits of body oils left on the surface (see Figure 13 ).

Experienced examiners fi nd that gray and black powders are adequate for most latent-print work; the examiner selects the powder that affords the best color contrast with the surface being dusted. Therefore, the gray pow- der, composed of an aluminum dust, is used on dark-colored surfaces. It is also applied to mirrors and metal surfaces that are polished to a mirrorlike fi n- ish because these surfaces photograph as black. The black powder, composed

CASEFILES THE NIGHT STALKER

Richard Ramirez committed his fi rst murder in June 1984. His victim was a 79-year-old woman who was stabbed repeatedly and sexually assaulted, and then her throat was slashed. It was eight months before

Ramirez killed again: In the spring of 1985, he began a murderous rampage that resulted in thirteen additional killings and fi ve rapes.

Ramirez’s modus operandi was to enter a home through an open window, shoot the male residents, and savagely rape female victims. He scribed a pentagram and the words “Jack the Knife” on a wall in the home of one of his victims and was reported by another to have forced her to “swear to Satan” during the assault. His identity yet unknown, the news media dubbed him the “Night Stalker.” As the body count continued to rise, public hysteria and a media frenzy prevailed.

The break in the case came when the license plate of what seemed to be a car related to a sighting of the Night Stalker was reported to the police. The police determined from the plate number that the car had been stolen and eventually located it, abandoned in a parking lot. After processing the car for prints, police found one usable partial fi ngerprint. This fi ngerprint was entered into the Los Angeles Police Department’s brand-new AFIS computerized fi ngerprint system.

Without AFIS, it would have taken a single technician, manually searching Los Angeles’ 1.7 million print cards, sixty-seven years to come up with the perpetrator’s prints. Thanks to AFIS, it took only a few seconds to match and identify them. The Night Stalker was iden- tifi ed as Richard Ramirez, who had been fi ngerprinted following a traffi c violation some years before. Police searching the home of one of his friends found the gun used to commit the murders, and jewelry belonging to his victims was found in the possession of Ramirez’s sister. Ramirez was convicted of murder and sentenced to death in 1989. He remains on death row.

Richard Ramirez, the Night Stalker. © Bettmann/CORBIS. All Rights Reserved.

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FINGERPRINTS

basically of black carbon or charcoal, is applied to white or light-colored surfaces.

Other types of powders are available for developing latent prints. A magnetic-sensitive powder can be spread over a surface using a magnet in the form of a Magna Brush. A Magna Brush does not have any bristles to come into contact with the surface, so there is less chance that the print will be destroyed or damaged. The magnet- sensitive powder comes in black and gray and is especially useful on such items as fi nished leather and rough plastics, on which the texture of the surface tends to hold particles of ordinary powder. Fluorescent powders are also used to develop latent fi ngerprints. These powders fl uoresce un- der ultraviolet light. By photographing the fl uorescence pattern of the developing print under UV light, it is possi- ble to see the print clearly in situations in which the color of the surface might otherwise obscure the print.

IODINE FUMING Of the several chemical methods used for visualizing latent prints, iodine fuming is the oldest. Iodine is a solid crystal that, when heated, converts into a vapor without passing through a liquid phase; such a transformation is called sublimation . Most often, the sus- pect material is placed in an enclosed cabinet along with iodine crystals (see Figure 14 ). As the crystals are heated, the resultant vapors fi ll the chamber and combine with constituents of the latent print to make it visible.

FIGURE 12 Using a Refl ected Ultraviolet Imaging System with the aid of a UV lamp to search for latent fi ngerprints. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www .sirchie.com

FIGURE 13 Developing a latent fi ngerprint on a surface by applying a fi ngerprint powder with a fi berglass brush. Courtesy Sirchie Finger- print Laboratories, Youngsville, NC, www.sirchie.com

FIGURE 14 A heated fuming cabinet. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

181

FINGERPRINTS

Unfortunately, iodine prints are not permanent and begin to fade once the fuming process is stopped. Therefore, the examiner must photograph the prints immediately upon development in order to retain a permanent record. Alternatively, iodine-developed prints can be fi xed by spraying them with a 1 percent solution of starch in water. The print then turns blue and lasts for several weeks to several months.

iodine fuming A technique for visualizing latent fi ngerprints by exposing them to iodine vapors.

CASEFILES THE MAYFIELD AFFAIR

On March 11, 2004, a series of ten explosions at four sites occurred on commuter trains traveling to or near the Atocha train station in Madrid, Spain. The death toll from these explosions was nearly 200, with more than 1,500 injured. On the day of the attack, a plastic bag was found in a van previously reported as stolen. The bag contained copper detonators like those used in the train bombs.

On March 17, the FBI received electronic images of latent fi ngerprints that were recovered from the plastic bag, and a search was initiated on the FBI’s IAFIS. A senior fi ngerprint examiner encoded seven minutiae points from the high-resolution image of one suspect latent fi ngerprint and initiated an IAFIS search, eventu- ally matching the print to Brandon Mayfi eld. Mayfi eld’s prints were in the FBI’s central database because they had been taken when he joined the military, where he served for eight years before being hon- orably discharged as a second lieutenant.

After a visual comparison of the suspect print and fi le prints, the examiner concluded a “100 percent match.” The identifi cation was verifi ed by a retired FBI fi ngerprint examiner with more than thirty years of experience who was working under contract with the bureau, as well as by a court-appointed independent fi ngerprint examiner (see the photos).

Mayfi eld, age 37, a Muslim convert, was arrested on May 6 on a material witness warrant. The US Attorney’s Offi ce came up with a list of Mayfi eld’s potential ties to Muslim terrorists, which they included in the affi davit they presented to the federal judge who ordered his arrest and detention. The document also said that, although no travel records were found for Mayfi eld, “It is believed that Mayfi eld may have traveled under a false or fi ctitious name.” On May 24, Spanish investigators linked the print from the plastic bag to an Algerian national, and

Mayfi eld’s case was thrown out. The FBI issued him a highly unusual offi cial apology, and his ordeal became a stunning embarrassment to the US government.

The Mayfi eld incident has been the subject of an investiga- tion by the Offi ce of the Inspector General (OIG), US Department of Justice ( www.usdoj.gov/oig/special/s0601/fi nal.pdf ). The OIG investigation concluded that a “series of systemic issues” in the FBI Laboratory contributed to the Mayfi eld misidentifi cation. The report noted that the FBI had since made signifi cant procedural modifi - cations to help prevent similar errors in the future, and it strongly supported the FBI’s decision to develop more objective standards for fi ngerprint identifi cation. An internal review of the FBI Latent Print Unit conducted in the aftermath of the Mayfi eld affair has resulted in the implementation of revisions in training as well as in the decision-making process for determining the comparative value of a latent print, along with more stringent verifi cation policies and procedures. 2

The impact of the Mayfi eld affair on fi ngerprint technology as currently practiced and the weight courts will assign to fi ngerprint matches in the future remain open questions.

(a) A questioned print recovered in connection with the Madrid bombing investigation. (b) A fi le print of Brandon Mayfi eld. (a) Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com; (b) Courtesy of Lightning Powder Co. Inc., Salem, OR

182

FINGERPRINTS

The reasons latent prints are visualized by iodine vapors are not yet fully understood. Many believe that the iodine fumes combine with fatty oils; how- ever, there is also convincing evidence that the iodine may actually interact with residual water left on a print from perspiration. 3

NINHYDRIN Another chemical used for visualizing latent prints is ninhydrin . The development of latent prints with ninhydrin results from its chemical reaction with amino acids present in trace amounts in perspiration, creating a purple-blue color. A ninhydrin (triketohydrindene hydrate) solution is commonly sprayed onto a porous surface from an aerosol can. The solution is prepared by mixing the ninhydrin powder with a suitable solvent, such as acetone or ethyl alcohol; a 0.6 percent solution appears to be effective for most applications.

Generally, prints begin to appear within an hour or two after ninhydrin application; however, weaker prints may be visualized after 24 to 48 hours. The development can be hastened if the treated specimen is heated in an oven or on a hot plate at a temperature of 80°C to 100°C. The ninhydrin method has developed latent prints on old paper after as long as fi fteen years.

PHYSICAL DEVELOPER Physical Developer is a third chemical mixture used for visualizing latent prints. Physical Developer is a silver nitrate–based liquid reagent. This method has gained wide acceptance by fi ngerprint examiners, who have found it effective for visualizing latent prints that remain undetected by the previously described methods. Also, this technique is very effective for developing latent fi ngerprints on porous articles that may have been wet at one time.

For most fi ngerprint examiners, the chemical method of choice is ninhy- drin. Its extreme sensitivity and ease of application have all but eliminated the use of iodine for latent-print visualization. However, when ninhydrin fails, development with Physical Developer may provide iden- tifi able results. Application of Physical Developer washes away any traces of proteins from an object’s surface; hence, if one wishes to use all of the previously mentioned chemical development methods on the same surface, it is necessary to fi rst fume with iodine, follow this treatment with ninhydrin, and then apply Physical Developer to the object.

SUPER GLUE FUMING In the past, chemical treatment for fi ngerprint development was reserved for porous sur- faces such as paper and cardboard. However, since 1982, a chemical technique known as Super Glue fuming has gained wide popularity for developing latent prints on nonporous surfaces such as metals, electrical tape, leather, and plastic bags (see Figure 15 ). 4

Super Glue is approximately 98 to 99 percent cyano- acrylate ester, a chemical that interacts with and visual- izes a latent fi ngerprint. Cyanoacrylate ester fumes can be created when Super Glue is placed on absorbent cotton treated with sodium hydroxide. The fumes can also be created by heating the glue. The fumes and the eviden- tial object are contained within an enclosed chamber for up to six hours. Development occurs when fumes from the glue adhere to the latent print, usually producing a white-appearing latent print. Interestingly, small enclosed areas, such as the interior of an automobile, have been successfully processed for latent prints with fumes from Super Glue.

sublimation A physical change from a solid directly into a gaseous state.

ninhydrin A chemical reagent used to develop latent fi ngerprints on porous materials by reacting with the amino acids in perspiration.

Physical Developer A silver nitrate–based reagent formulated to develop latent fi ngerprints on porous surfaces.

Super Glue fuming A technique for visualizing latent fi ngerprints on nonporous surfaces by exposing them to cyanoacrylate vapors; named for the commercial product Super Glue.

FIGURE 15 Super Glue fuming a nonporous metallic surface in the search for latent fi ngerprints. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

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FINGERPRINTS

Through the use of a small handheld wand, cyanoacrylate fuming is now easily done at a crime scene or in a laboratory setting. The wand heats a small cartridge containing cyanoacrylate. Once heated, the cyanoacrylate vaporizes, allowing the operator to direct the fumes onto the suspect area (see Figure 16 ).

OTHER TECHNIQUES FOR VISUALIZATION In recent years, researchers have ex- plored a variety of new processes applicable to the visualization of latent fi nger- prints. However, for many years progress in this fi eld was minimal. Fingerprint specialists traditionally relied on three chemical techniques— iodine, ninhydrin, and silver nitrate—to reveal a hidden fi ngerprint. Then, Super Glue fuming extended chemical development to prints deposited on nonporous surfaces.

Another hint of things to come emerged with the discovery that latent fi ngerprints could be visualized by exposure to laser light. This laser method took advantage of the fact that perspiration contains a variety of components that fl uoresce when illuminated by the light of a laser.

The next advancement in latent-fi ngerprint development occurred with the discovery that fi ngerprints could be treated with chemicals that would induce fl uorescence when exposed to laser illumination. For example, applica- tion of zinc chloride after ninhydrin treatment or application of the dye rho- damine 6G after Super Glue fuming causes fl uorescence and increased the sensitivity of detection on exposure to laser illumination. The discovery of nu- merous chemical developers for visualizing fi ngerprints through fl uorescence quickly followed. This knowledge set the stage for the next advance in latent- fi ngerprint development: the alternate light source .

With the advent of chemically induced fl uorescence, lasers were no lon- ger needed to induce fi ngerprints to fl uoresce through perspiration residues. High-intensity light sources, or alternate light sources, have proliferated and all but replaced laser lights (see Figure 17 ). High-intensity quartz halogen or xenon-arc light sources can be focused on a suspect area through a fi ber- optic cable. This light can be passed through several fi lters, giving the user more fl exibility in selecting the wavelength of light to be aimed at the latent print. Alternatively, lightweight, portable alternate light sources that use light- emitting diodes (LEDs) are also commercially available (see Figure 18 ).

In most cases, these light sources have proved as effective as laser light in developing latent prints, and they are commercially available at costs signifi - cantly below those of laser illuminators. Furthermore, these light sources are portable and can be readily taken to any crime scene.

FIGURE 16 (a) A handheld fuming wand uses disposable cartridges containing cyanoacrylate. The wand is used to develop prints at the crime scene and (b) in the laboratory. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

fl uoresce To emit visible light when exposed to light of a shorter wavelength.

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A large number of chemical treatment processes are available to the fi ngerprint examiner, and the fi eld is in a constant state of fl ux. Selection of an appro- priate procedure is best left to technicians who have developed their skills through casework experience. Newer chemical processes include a substitute for ninhydrin called DFO (1,8-diazafl uoren-9-one). This chemical visualizes latent prints on porous materials when exposed to an alternate light source. DFO has been shown to develop two and a half times more la- tent prints on paper than ninhydrin. 1,2- indanedione is also emerging as a potential reagent for the de- velopment of latent fi ngerprints on porous surfaces. 1,2-indanedione gives both good initial color and strong fl uorescence when it reacts with amino acids derived from prints, and thus it has the potential to provide in one process what ninhydrin and DFO can do in two steps. Dye combinations known as RAM, RAY, and MRM 10, when used in conjunction with Super Glue fuming, have been effective in visualizing latent fi ngerprints by fl uorescence.

FIGURE 17 An alternate light source system incorporating a high-intensity light source. Courtesy Foster & Freeman Limited, Worcestershire, UK, www.fosterfreeman.co.uk

FIGURE 18 A lightweight handheld alternate light source that uses LEDs. Courtesy Foster & Freeman Limited, Worcestershire, UK, www. fosterfreeman.co.uk

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Studies have demonstrated that common fi ngerprint-developing agents do not interfere with DNA-testing methods used for characterizing blood- stains. 5 Nonetheless, in cases involving items with material adhering to their surfaces and/or items that will require further laboratory examinations, fi n- gerprint processing should not be performed at the crime scene. Rather, the items should be submitted to the laboratory, where they can be processed for fi ngerprints in conjunction with other necessary examinations.

Quick Review • Visible prints are made when fi ngers touch a surface after the ridges have

been in contact with a colored material such as blood, paint, grease, or ink. • Plastic prints are ridge impressions left on a soft material, such as putty,

wax, soap, or dust. • Latent prints deposited on hard and nonabsorbent surfaces (such as glass,

a mirror, tile, and painted wood) are usually developed by the application of a powder, whereas prints on porous surfaces (such as papers and card- board) generally require treatment with a chemical.

• Examiners use various chemical methods to visualize latent prints, such as iodine fuming, ninhydrin, and Physical Developer.

• Super Glue fuming develops latent prints on nonporous surfaces. • Latent fi ngerprints can also be treated with chemicals that induce fl uores-

cence when exposed to a high-intensity light or an alternate light source.

CLOSER ANALYSIS FLUORESCENCE

Fluorescence occurs when a substance absorbs light and reemits the light in wavelengths longer than that of the illuminating source. Im- portantly, substances that emit light or fl uoresce are more readily

seen either with the naked eye or through photography than are non- light-emitting materials. The high sensitivity of fl uorescence serves as the underlying principle of many of the new chemical techniques used to visualize latent fi ngerprints.

The earliest use of fl uorescence to visualize fi ngerprints came with the direct illumination of a fi ngerprint with argon-ion lasers. This laser type was chosen because its blue-green light induced some of the perspiration components of a fi ngerprint to fl uoresce (see fi gure). The major drawback of this approach is that the perspiration compo- nents of a fi ngerprint are often present in quantities too minute to observe even with the aid of fl uorescence.

The fi ngerprint examiner, wearing safety goggles containing optical fi lters, visually examines the specimen being exposed to the laser light. The fi lters absorb the laser light and permit the wave- lengths at which latent-print residues fl uoresce to pass through to the eyes of the wearer. The fi lter also protects the operator against eye damage from scattered or refl ected laser light. Likewise, latent- print residue producing suffi cient fl uorescence can be photographed by placing this same fi lter across the lens of the camera. Examination of specimens and photography of the fl uorescing latent prints are carried out in a darkened room.

Directional mirror Laser

Dispersal lens

Barrier filter Observer

A schematic depicting latent-print detection with the aid of a laser. Courtesy Federal Bureau of Investigation, Washington, DC

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FINGERPRINTS

FIGURE 19 A camera fi tted with an adapter designed to give an approximate 1:1 photograph of a fi nger- print. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

Preservation of Developed Prints Once the latent print has been visualized, it must be permanently preserved for future comparison and possible use in court as evidence. A photograph must be taken before any further attempts at preservation. Any camera equipped with a close-up lens will do; however, many investigators prefer to use a camera spe- cially designed for fi ngerprint photography. Such a camera comes equipped with a fi xed focus to take photographs on a 1:1 scale when the camera’s open eye is held exactly fl ush against the print’s surface (see Figure  19 ). In addition, photographs must be taken to provide an overall view of the print’s location with respect to other evidential items at the crime scene.

Once photographs have been secured, one of two procedures is followed. If the object is small enough to be transported without destroying the print, it should be preserved in its entirety. The print should be covered with cellophane so it will be protected from damage. On the other hand, prints on large immovable objects that have been developed with a powder can best be preserved by “lifting.” The most popular type of lifter is a broad adhesive tape similar to Scotch tape. Fingerprint powder is applied to the print, and the sur- face containing the print is covered with the adhesive side of the tape. When the tape is pulled up, the powder is transferred to the tape. Then the tape is placed on a properly labeled card that provides a good background contrast with the powder.

A variation of this procedure is the use of an adhesive-backed clear plastic sheet attached to a colored cardboard backing. Before it is applied to the print, a celluloid separator is peeled from the plastic sheet to expose the adhesive lifting surface. The tape is then pressed evenly and fi rmly over the powdered print and pulled up (see Figure 20 ). The sheet containing the adhering powder is then pressed against the cardboard backing to provide a permanent record of the fi ngerprint.

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FINGERPRINTS

Digital Imaging for Fingerprint Enhancement When fi ngerprints are lifted from a crime scene, they are not usually in per- fect condition, which can make analysis diffi cult. As computers have advanced technology in most fi elds, fi ngerprint imaging has not been left behind. With the help of digital imaging software, fi ngerprints can now be enhanced for the most accurate and comprehensive analysis.

Digital imaging is the process by which a picture is converted into a digi- tal fi le. The image produced from this digital fi le is composed of numerous square electronic dots called pixels . Images composed of only black and white elements are referred to as grayscale images . Each pixel is assigned a number according to its intensity, ranging from 0 (black) to 255 (white), and together these shaded pixels create an image. Once an image is digitally stored, it can be manipulated by computer software that changes the numerical value of each pixel, thus altering the image as directed by the user. The resolution is the degree of detail that can be seen in an image. It is defi ned in terms of dimen- sions, such as 800 � 600 pixels. The larger the numbers, the more closely the digital image resembles the real-world image.

The input of pictures into a digital imaging system is usually done through the use of scanners, digital cameras, and video cameras. After the picture is converted into a digital image, several methods can be employed to enhance it. The overall brightness of an image, as well as the contrast between the image and the background, can be adjusted through contrast-enhancement methods. One approach used to enhance an image is spatial fi ltering , in which several types of fi lters produce various effects. A low-pass fi lter is used to eliminate harsh edges by reducing the intensity difference between pixels. A high-pass fi lter operates by modifying a pixel’s numerical value to exagger- ate the difference between its intensity and that of its neighbor. The result- ing effect increases the contrast of the edges, thus providing a high contrast between the elements and the background. Frequency analysis, also referred to as frequency Fourier transform (FFT), is used to identify periodic or repeti- tive patterns such as lines or dots that interfere with the interpretation of the image. These patterns are diminished or eliminated to enhance the appear- ance of the image. Interestingly, the spaces between fi ngerprint ridges are themselves periodic. Therefore, the fi ngerprint can be identifi ed apart from its background in FFT mode and then enhanced. Likewise, if ridges from over- lapping prints are positioned in different directions, their corresponding fre- quency information is at different locations in FFT mode. The ridges of one latent print can then be enhanced while the ridges of the other are suppressed.

digital imaging A process through which a picture is converted into a series of square electronic dots known as pixels.

pixel A square electronic dot that is used to compose a digital image.

FIGURE 20 “Lifting” a fi nger- print. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

188

FINGERPRINTS

FIGURE 21 A fi ngerprint being enhanced in Adobe Photoshop. In this example, on the left is the original scan of an inked fi ngerprint on a check. On the right is the same image after eliminating the green security background using Adobe Photoshop’s Channel Mixer. Courtesy Imaging Forensics, Fountain Valley, CA, www.imaging-forensics.com

Color interferences can pose a problem when analyzing an image. For example, a latent fi ngerprint found on paper currency or a check may be  diffi cult to analyze because of the distracting colored background. With the imaging software, the colored background can simply be removed to make the image stand out (see Figure 21 ). If the image itself is a particular color, such as a ninhydrin-developed print, the color can be isolated and enhanced to distin- guish it from the background.

Digital imaging software also provides functions in which portions of the im- age can be examined individually. With a scaling and resizing tool, the user can se- lect a part of an image and resize it for a closer look. This function operates much like a magnifying glass, helping the examiner view the fi ne details of an image.

An important and useful tool, especially for fi ngerprint identifi cation, is the compare function. This specialized feature places two images side by side and al- lows the examiner to chart the common features in both images simultaneously (see Figure 22 ). The zoom function is used in conjunction with the compare tool. As the examiner viewing the image on the screen zooms in to a portion of one image, the software automatically zooms in to the second image for comparison.

Digital imaging is undoubtedly an effective tool for enhancing and analyz- ing images, and the benefi ts of digital enhancement methods are apparent when weak images are made more distinguishable. However, the tools are only as useful as the images they have to work with. If the details do not exist on the original images, the enhancement procedures are not going to work.

Quick Review • Once a latent print has been visualized, it must be permanently preserved

for future comparison and for possible use as court evidence. A photo- graph must be taken before any further attempts at preservation are made.

• A common method for preserving a print developed with a powder is lift- ing the print with an adhesive tape.

• Digital imaging is a process in which a picture is converted into a series of square electronic dots known as pixels. Fingerprints can be enhanced with digital imaging.

189

FINGERPRINTS

FIGURE 22 Current imaging software allows fi ngerprint analysts to prepare a fi ngerprint comparison chart. The fi ngerprint examiner can compare prints side by side and display important features that are consistent between the fi ngerprints. This sort of digital display can be created in about thirty to sixty minutes. Courtesy Imaging Forensics, Fountain Valley, CA, www.imaging-forensics.com

CHAPTER REVIEW

• Fingerprints are a reproduction of friction skin ridges found on the palm side of the fi ngers and thumbs.

• The basic principles underlying the use of fi ngerprints in criminal investigations are as follows: (1) A fi ngerprint is an individual characteristic because no two fi ngers have yet been found to possess identical ridge characteristics, (2) a fi ngerprint remains unchanged during an individual’s life- time, and (3) fi ngerprints have general ridge patterns that permit them to be systematically classifi ed.

• All fi ngerprints are divided into three classes on the basis of their general pattern: loops, whorls, and arches.

• The individuality of a fi ngerprint is determined not by its general shape or pattern but by a careful study of its ridge characteristics. The expert must demonstrate a point-by-point comparison in order to prove the identity of an individual.

• A four-step process known as ACE-V (analysis, compari- son, evaluation, and verifi cation) is used to identify and individualize a fi ngerprint.

• The fi nal step in the process involves verifi cation of the examiner’s conclusion by a second examiner.

• When a fi nger touches a surface, perspiration and oils are transferred onto that surface, leaving a fi ngerprint. Prints deposited in this manner are invisible to the eye and are commonly referred to as latent or invisible fi ngerprints.

• The primary classifi cation is the fi rst step in classifying fi ngerprints under the FBI system. The presence or absence of the whorl pattern is the basis for the determination of the primary classifi cation.

• The fi ngerprint database known as AFIS converts an image of a fi ngerprint into digital minutiae that contain data showing ridges at their points of termination (i.e., ridge endings) and of branching into two ridges (i.e., bifurcations).

• AFIS makes no fi nal decisions on the identifi cation of a fi n- gerprint, instead leaving this function to a trained examiner.

• Live Scan is an inkless device that captures digital images of fi ngerprints and palm prints and electronically transmits them to an AFIS.

• Visible prints are made when fi ngers touch a surface after the ridges have been in contact with a colored material such as blood, paint, grease, or ink.

VIRTUAL LAB Fingerprinting To perform a virtual fi ngerprinting analysis, go to www.pearsoncustom .com/us/vlm/

190

• Plastic prints are ridge impressions left on a soft material, such as putty, wax, soap, or dust.

• Latent prints deposited on hard and nonabsorbent surfaces (such as glass, a mirror, tile, and painted wood) are usually developed by the application of a powder, whereas prints on porous surfaces (such as papers and cardboard) generally require treatment with a chemical.

• Examiners use various chemical methods to visualize latent prints, such as iodine fuming, ninhydrin, and Physical Developer.

• Super Glue fuming develops latent prints on nonporous surfaces.

• Latent fi ngerprints can also be treated with chemicals that induce fl uorescence when exposed to a high-intensity light or an alternate light source.

• Once a latent print has been visualized, it must be perma- nently preserved for future comparison and for possible use as court evidence. A photograph must be taken before any further attempts at preservation are made.

• A common method for preserving a print developed with a powder is lifting the print with an adhesive tape.

• Digital imaging is a process in which a picture is converted into a series of square electronic dots known as pixels. Fingerprints can be enhanced with digital imaging.

FINGERPRINTS

REVIEW QUESTIONS

1. The fi rst systematic attempt at personal identifi cation was devised and introduced by ______________ .

2. A system of identifi cation relying on precise body measure- ments is known as ______________ .

3. The fi rst book written on the subject of fi ngerprints, called Finger Prints, was written in 1892 by ______________ and discussed the anatomy of fi ngerprints and suggested meth- ods for recording them.

4. The fi ngerprint classifi cation system used in most English- speaking countries was devised by ______________ .

5. True or False: The fi rst systematic and offi cial use of fi nger- prints for personal identifi cation in the United States was adopted by the New York City Civil Service Commission. ______________

6. The ______________ has the largest collection of fi nger- prints in the world.

7. Galton calculated that approximately ______________ different fi ngerprints could exist, and current fi gures are similarly high.

8. True or False: The individuality of a fi ngerprint is determined by its pattern. ______________

9. A point-by-point comparison of a fi ngerprint’s ______________ must be demonstrated in order to prove identity.

10. ______________ are a reproduction of friction skin ridges.

11. The form and pattern of skin ridges are determined by the skin layer called the ______________ .

12. Fingerprints deposited on a surface when oils and sweat are excreted from pores on the friction ridges are called ______________ fi ngerprints.

13. A permanent scar forms in the skin only when an injury damages the ______________ .

14. True or False: Fingerprints cannot be changed during a person’s lifetime. ______________

15. The three general patterns into which fi ngerprints are divided are ______________ , ______________ , and ______________ .

16. The most common fi ngerprint pattern is the ______________ .

17. Approximately 5 percent of the population has the ______________ fi ngerprint pattern.

18. A loop pattern that opens toward the thumb is known as a(n) ______________ loop.

KEY TERMS

anthropometry

arch

digital imaging

fl uoresce

iodine fuming

latent fi ngerprint

Live Scan

loop

ninhydrin

Physical Developer

pixel

plastic print

portrait parlé

ridge characteristics (minutiae)

sublimation

Super Glue fuming

visible print

whorl

191

19. The pattern area of the loop is enclosed by two diverging ridges known as ______________ .

20. The ridge point nearest the type-line divergence is known as the ______________ .

21. True or False: All loops must have two deltas. ______________

22. The approximate center of a loop pattern is called the ______________ .

23. A whorl pattern has ______________ deltas and at least ______________ ridge(s) that make a complete circuit.

24. If an imaginary line drawn between the two deltas of a whorl pattern touches any of the spiral ridges, the pattern is classi- fi ed as a(n) ______________ .

25. The simplest of all fi ngerprint patterns is the ______________ .

26. True or False: Arches have type lines, deltas, and cores. ______________

27. The presence or absence of the ______________ pattern is used as a basis for determining the primary classifi cation in the Henry system.

28. The largest category (25 percent) of the population has a ______________ primary classifi cation, meaning all their fi ngers have loops or arches.

29. True or False: A fi ngerprint classifi cation system can unequiv- ocally identify an individual. ______________

30. True or False: Computerized fi ngerprint search systems match prints by comparing the positions of bifurcations and ridge endings. ______________

31. By determining the degree of correlation between the loca- tion and relationship of the ______________ for both the search and fi le fi ngerprints, a computer can make thousands of fi ngerprint comparisons in a second.

32. The digital-capture device called ______________ has eliminated ink and paper for the collection of fi le fi ngerprints.

33. A fi ngerprint left by a person with soiled or stained fi ngertips is called a(n) ______________ .

34. ______________ fi ngerprints are impressions left on a soft material.

35. Fingerprints on hard and nonabsorbent surfaces are best developed by the application of a(n) ______________ .

36. Fingerprints on porous surfaces are best developed with ______________ treatment.

37. ______________ vapors chemically combine with fatty oils or residual water to visualize a fi ngerprint.

38. The chemical ______________ visualizes fi ngerprints by its reaction with amino acids.

39. Chemical treatment with ______________ visualizes fi ngerprints on porous articles that may have been wet at one time.

40. True or False: A latent fi ngerprint is fi rst treated with Physical Developer followed by ninhydrin. ______________

41. A chemical technique known as ______________ is used to develop latent prints on nonporous surfaces such as metal and plastic.

42. ______________ occurs when a substance absorbs light and reemits the light in wavelengths longer than the illumi- nating source.

43. High-intensity light sources, known as ______________ , are effective in developing latent fi ngerprints.

44. Once a fi ngerprint has been visualized, it must fi rst be pre- served by ______________ .

45. Fingerprints on large immovable objects that have been developed with a powder can best be preserved by ______________ with a broad adhesive tape similar to Scotch tape.

FINGERPRINTS

192

APPLICATION AND CRITICAL THINKING

1. Classify each of the following prints as loop, whorl, or arch.

(1). (2).

(5). (6).

(3). (4).

FINGERPRINTS

2. Following is a description of the types of prints from the fi n- gers of a criminal suspect. Using the FBI system, determine the primary classifi cation of this individual.

Finger Right Hand Left Hand Thumb Whorl Whorl Index Loop Whorl Middle Whorl Arch Ring Whorl Whorl Little Arch Whorl

3. While searching a murder scene, you fi nd the following items that you believe may contain latent fi ngerprints. Indicate whether prints on each item should be developed using fi n- gerprint powder or chemicals.

a. A leather sofa

b. A mirror

c. A painted wooden knife handle

d. Blood-soaked newspapers

e. A revolver

4. Criminalist Frank Mortimer is using digital imaging to en- hance latent fi ngerprints. Indicate which features of digital imaging he would most likely use for each of the following tasks:

a. Isolating part of a print and enlarging it for closer ex- amination

b. Increasing the contrast between a print and the back- ground surface on which it is located

c. Examining two prints that overlap each other

5. The following are fi ngerprint patterns of three men and a woman with criminal records for robbery. Identify the fol- lowing fi ngerprints according to the three groups and the subgroups of fi ngerprints.

6. Count the number of bifurcations in the following prints. Choose between 9, 11, and 13.

Number of bifurcations:

Ivan

Lisa Charlie

KJ

193

7. At the Museum of Culture Studies, a diary that belonged to Martin Luther King Jr. has been stolen and replaced by a fake. The only evidence is a fi ngerprint impression left by the thief on the fake diary. The police suspect four individuals who have had previous criminal records for similar crimes.

Their fi ngerprints already exist in the police database. KJ,  Ivan, Lisa, and Charlie are the four suspects. Carefully examine the criminal’s fi ngerprint impression and identify the suspect fi ngerprint that matches the most closely with it.

FINGERPRINTS

Crime Scene Fingerprint

ENDNOTES

1. A tented arch is also any pattern that resembles a loop but lacks one of the essential requirements for classifi cation as a loop.

2. Smrz, M. A., et al., “Review of FBI Latent Print Unit Processes and Recommendations to Improve Practices and Quality,” Journal of Forensic Identifi cation 56 (2006): 402–433.

3. J. Almag, Y. Sasson, and A. Anati, “Chemical Reagents for the Development of Latent Fingerprints II: Controlled Addition of Water Vapor to Iodine Fumes—A Solution to the Aging Problem,” Journal of Forensic Sciences 24 (1979): 431.

4. F. G. Kendall and B. W. Rehn, “Rapid Method of Super Glue Fuming Application for the Development of Latent Fingerprints,” Journal of Forensic Sciences 28 (1983): 777.

5. C. Roux et al., “A Further Study to Investigate the Effect of Fingerprint Enhancement Techniques on the DNA Analysis of Bloodstains,” Journal of Forensic Identifi cation 49 (1999): 357; C. J. Frégeau et al., “Fingerprint Enhancement Revisited and the Effects of Blood Enhancement Chemicals on Subsequent Profi ler Plus™ Fluorescent Short Tandem Repeat DNA Analysis of Fresh and Aged Bloody Fingerprints,” Journal of Forensic Sciences 45 (2000): 354; P. Grubwieser et al., “Systematic Study on STR Profi ling on Blood and Saliva Traces after Visualization of Fingerprints,” Journal of Forensic Sciences 48 (2003): 733.

Ivan Lisa CharlieKJ

194

THE BELTWAY SNIPERS During a three-week period in October 2002, ten people were killed and three others wounded as two snipers terrorized the region in and around the Baltimore/ Washington metropolitan area. The arrest of John Allen Muhammad, 41, and Lee Boyd Malvo, 17, ended the ordeal. The semiautomatic .223-caliber rifl e seized from them was ultimately linked by fi rearm tests to eight of the ten killings. The car that Muhammad and Malvo were driving had been specially adapted with one hole in the

trunk through which a rifl e barrel could protrude, so that a sniper could shoot from inside the slightly ajar trunk.

The major break in the case came when a friend of Muhammad’s called police suggesting that Muhammad and his friend Malvo were the likely snipers. Muhammad’s automobile records revealed numerous traffi c stops in the Beltway area during the time of the shootings. Another break in the case came when Malvo called a priest to boast of a killing that had occurred weeks before, in Montgomery, Alabama. Investigators traced the claim to a recent liquor store holdup that left one person dead. Fortunately, the perpetrator of this crime left a latent fi ngerprint at the murder scene. Authorities quickly tracked the print to Malvo, a Jamaican citizen,

through his fi ngerprints on fi le with the Immigration and Naturalization Service. A description of Muhammad’s car was released to the media, leading to tips from alert citizens who noticed the car parked in a rest area with both occupants asleep.

The motive for the shooting spree was believed to be a plot to extort $10 million from local and state govern- ments. Muhammad was sentenced to death, and Malvo is currently serving life imprisonment without parole.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Describe techniques for rifl ing a barrel. • Recognize the class and individual characteristics of bullets

and cartridge cases. • Understand the use of the comparison microscope to compare

bullets and cartridge cases. • Explain the concept of the NIBIN database. • Explain the procedure for determining how far from a target

a weapon was fi red. • Identify the laboratory tests for determining whether an

individual has fi red a weapon. • Explain the forensic signifi cance of class and individual

characteristics to the comparison of tool mark, footwear, and tire impressions.

• List some common fi eld reagents used to enhance bloody footprints.

Firearms,

Tool Marks, and Other

Impressions Image courtesy of National Atlas

From Chapter 9 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

J ust as natural variations in skin ridge patterns and characteristics provide a key to human identifi cation, minute random markings on surfaces can impart individuality to inanimate objects. Structural variations and irregu-

larities caused by scratches, nicks, breaks, and wear permit the criminalist to relate a bullet to a gun, a scratch or abrasion mark to a single tool, or a tire track to a particular automobile. Individualization, so vigorously pursued in all other areas of criminalistics, is frequently attainable in fi rearms and tool mark examination.

Although a portion of this chapter will be devoted to the comparison of surface features for the purpose of bullet identifi cation, a complete description of the services and capabilities of the modern forensic fi rearms laboratory cannot be restricted to just this one subject, important as it may be. The high frequency of shooting cases means that the science of fi rearms identifi cation must extend beyond mere comparison of bullets to include knowledge of the operation of all types of weapons, restoration of obliterated serial numbers on weapons, detection and characterization of gunpowder residues on garments and around wounds, estimation of muzzle-to-target distances, and detec- tion of powder residues on hands. Each of these functions will be covered in this chapter.

Types of Firearms Generally, fi rearms can be divided into two categories: handguns and long guns. Handguns , or pistols, are fi rearms that are designed to be held and fi red with one hand. The three most common types of handguns are single-shot hand- guns, revolvers, and semiautomatics. All handguns can be classifi ed as single- action or double-action fi rearms. Single-action fi rearms require the hammer to

be manually cocked backward each time before the trigger is pulled in order to fi re. Double-action fi re- arms cock the hammer when the trigger is pulled and then reload the fi ring chamber after the round is fi red.

Single-shot pistols can fi re only one round, or shot, at a time. Each round must be manually loaded into the chamber before fi ring.

The revolver features several fi ring chambers located within a revolving cylinder. As the revolver is fi red, the cylinder can rotate clockwise or counter- clockwise. Each fi ring chamber holds one cartridge, which is lined up with the barrel mechanically when the round is fi red. The cartridge cases have to be man- ually ejected to reload the fi ring chambers. Swing- out revolvers feature a cylinder that swings out to the side of the weapon to be loaded (see Figure  1 ). Break-top revolvers are hinged so that both the bar- rel and the cylinder fl ip downward for loading. Solid- frame revolvers have no mechanism to uncover all the fi ring chambers at once. Instead a small “gate” at the back of the gun allows one chamber to be loaded at a time; the cylinder is then rotated, and the next chamber is loaded with a cartridge.

Semiautomatic pistols feature a removable magazine that is most often contained within the grip of the fi rearm. Once the magazine is loaded, the hammer is cocked by pulling the slide on the top of the gun rearward and then releasing it to load the fi rst round. The fi ring of the cartridge generates

fi rearms identifi cation A discipline primarily concerned with determining whether a bullet or cartridge was fi red by a particular weapon.

FIGURE 1 A swing-out revolver features a cylinder that swings out to the side of the weapon to be loaded.

196

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

gases that are used to eject the cartridge case, cock the hammer, and load the next round. A semiautomatic pistol (see Figure 2 ) fi res one shot per trigger pull. An automatic fi rearm, such as a machine gun, fi res as long as the trigger is pressed or until the ammunition is depleted.

Long guns are either rifl es or shotguns. Rifl es and shotguns are designed to be fi red while rest- ing on the shoulder. The two principal differences between rifl ed fi rearms and shotguns are found in the ammunition and the barrel. Shotgun ammuni- tion, called a shell, contains numerous ball-shaped projectiles, called shot. The barrel of a shotgun is smooth without the grooves and lands found in rifl es. A shotgun barrel can also be narrowed toward the muzzle in order to concentrate shot when fi red. This narrowing of the barrel is called the choke of the shot- gun. A shotgun may be single or double barreled. The two barrels of a double-barreled shotgun may be ar- ranged horizontally (side by side) or vertically (one over another). The barrels may also have different choke diameters.

The various types of rifl es and shotguns have different reloading mecha- nisms. The single-shot gun can chamber and fi re only one round at a time. Just as with single-shot pistols, the round has to be loaded manually each time. Repeating long guns use a mechanical instrument of some sort to eject spent cartridges, load a new round, and cock the hammer after a round is fi red. These include lever-action, pump or slide-action, bolt-action (see Figure 3 ), and semiautomatic (see Figure 4 ) long guns, the names of which refer to the loading mechanism used on each. Semiautomatic rifl es use the force of the gas produced during fi ring to eject the spent cartridge, load a new round, and cock the hammer. Semiautomatic fi rearms use a disconnector mecha- nism to fi re one shot per trigger pull, whereas fully automatic fi rearms do not have such a mechanism and fi re multiple consecutive shots with a sin- gle pull of the trigger.

Bullet and Cartridge Comparisons The inner surface of the rifl ed barrel of a gun leaves its markings on a bullet passing through it. These markings are particular to each gun. Hence, if one bullet found at the scene of a crime and another test-fi red from a suspect’s gun exhibit the same markings, the suspect is linked to the crime. Because these inner surface markings, or striations, are so important for bullet comparison, it is important to know why and how they originate.

FIGURE 2 A semiautomatic pistol. © Dorling Kindersley

FIGURE 3 A bolt-action long gun uses the movement of a bolt mechanism to expel the spent cartridge case, load the next round, and cock the hammer. Getty Images, Inc./Hulton Archive Photos

197

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

THE GUN BARREL

The gun barrel is produced from a solid bar of steel that has been hollowed out by drilling. The mi- croscopic drill marks left on the barrel’s inner surface are randomly irregular and in themselves impart a uniqueness to each barrel. How- ever, the manufacture of a bar- rel requires the additional step of impressing its inner surface with spiral grooves , a step known as

rifl ing . The surfaces of the original bore remaining between the grooves are called lands (see Figure 5 ).

As a fi red bullet travels through a barrel, it engages the rifl ing grooves. These grooves then guide the bullet through the barrel, giving it a rapid spin. This is done because a spinning bullet does not tumble end over end on leav- ing the barrel, but instead remains on a true and accurate course.

The diameter of the gun barrel, shown in Figure 6 , is measured between opposite lands and is known as the caliber of the weapon. Caliber is normally recorded in hundredths of an inch or in millimeters—for example, .22 caliber and 9 millimeter. Actually, the term caliber , as it is commonly applied, is not an exact measurement of the barrel’s diameter; for example, a .38-caliber weapon might actually have a bore diameter that ranges from 0.345 to 0.365 inch.

RIFLING METHODS Before 1940, barrels were rifl ed by having one or two grooves at a time cut into the surface with steel hook cutters. The cutting tool was rotated as it passed down the barrel, so that the fi nal results were grooves spiraling to either the right or left. However, as the need for increased speed and effi ciency in methods of weapons manufacture became apparent, newer techniques were developed that were far more suitable for mass production.

The broach cutter, shown in Figure 7 , consists of a series of concentric steel rings, with each ring slightly larger than the preceding one. As the broach passes through the barrel, it simultaneously cuts all grooves into the barrel at the required depth. The broach rotates as it passes through the barrel, giving the grooves their desired direction and rate of twist.

In contrast to the broach, the button process involves no cuttings. A steel plug or “button” impressed with the desired number of grooves is forced under extremely high pressure through the barrel. A single pass of the but- ton down the barrel compresses the metal to create lands and grooves on the barrel walls

FIGURE 4 A semiautomatic long gun uses the energy from the fi ring reaction to expel the spent cartridge case, load the next round, and cock the hammer. Tim Ridley © Dorling Kindersley, Courtesy of the Ministry of Defence Pattern Room, Nottingham

FIGURE 5 Interior view of a gun barrel, showing the presence of lands and grooves.

grooves The cut or low-lying portions between the lands in a rifl ed bore.

rifl ing The spiral grooves formed in the bore of a fi rearm barrel that impart spin to the projectile when it is fi red.

bore The interior of a fi rearm barrel.

lands The raised portion between the grooves in a rifl ed bore.

FIGURE 6 A cross-section of a barrel with six grooves. The diameter of the bore is the caliber.

caliber The diameter of the bore of a rifl ed fi rearm, usually expressed in hundredths of an inch or millimeters—for example, .22 caliber and 9 millimeter.

198

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

that are negative forms of those on the button. The button rotates to produce the desired direction and rate of twist (see Figure 8 ).

Like the button process, the mandrel-rifl ing hammer-forging process in- volves no cutting of metal. A mandrel is a rod of hardened steel machined so its form is the reverse impression of the rifl ing it is intended to produce. The mandrel is inserted into a slightly oversized bore, and the barrel is com- pressed with hammering or heavy rollers into the mandrel’s form.

Every fi rearms manufacturer chooses a rifl ing process that is best suited to meet the production standards and requirements of its product. Once the choice is made, however, the class characteristics of the weapon’s barrel remain consistent; each has the same number of lands and grooves, with the same approximate width and direction of twist. For example, .32-caliber

FIGURE 7 A segment of a broach cutter. Courtesy Susan Walsh, AP Wide W orld Photos

FIGURE 8 ( top ) Cross-section of a .22-caliber rifl ed barrel. ( bottom ) A button used to produce the lands and grooves in the barrel.

199

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

Smith & Wesson revolvers have fi ve lands and grooves twisting to the right. On the other hand, Colt .32-caliber revolvers exhibit six lands and grooves twisting to the left. Although these class charac- teristics permit the examiner to distinguish one type or brand name of weapon from another, they do not impart individuality to any one barrel; no class characteristic can do this.

If one could cut a barrel open lengthwise, careful examination of the interior would reveal the existence of fi ne lines, or stria- tions, running the length of the barrel’s lands and grooves. These striations are impressed into the metal as the negatives of min- ute imperfections found on the rifl ing cutter’s surface, or they are produced by minute chips of steel pushed against the barrel’s in- ner surface by a moving broach cutter. The random distribution and irregularities of these markings are impossible to duplicate exactly in any two barrels. No two rifl ed barrels, even those man- ufactured in succession, have identical striation markings. These striations form the individual characteristics of the barrel.

COMPARING BULLET MARKINGS As the bullet passes through the barrel, its surface is impressed with the rifl ed markings of the barrel. The bullet emerges from the barrel carrying the im- pressions of the bore’s interior surface (see Figure 9 ). Because there is no practical way to directly compare the markings on the fi red bullet and those within a barrel, the examiner must obtain test bullets fi red through the suspect barrel for comparison. To prevent damage to the test bullet’s markings and to facilitate the bullet’s recovery, test fi rings are normally made into a recovery box fi lled with cotton or into a water tank (see Figure 10 ).

WebExtra 1

Practice Matching Bullets With the Aid of a 3-D Interactive Illustration www.mycrimekit.com

FIGURE 10 In ballistics testing, a suspect fi rearm is fi red into a water tank. The bullet is slowed and stopped by the water, fi shed out undamaged, and compared to bullets from the crime scene. Courtesy Mikael Karlsson/Arresting Images

FIGURE 9 A bullet is impressed with the rifl ing markings of the barrel when it emerges from the weapon.

200

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

The number of lands and grooves and their direction of twist are obvious points of comparison during the initial stages of the examination. Any differences in these class character- istics immediately eliminate the possibility that both bullets traveled through the same barrel. A bullet with fi ve lands and grooves could not possibly have been fi red from a weapon of like caliber with six lands and grooves, nor could one having a right twist have come through a barrel impressed with a left twist. If both bullets carry the same class characteristics, the analyst must then begin to match the striated markings on both bullets. This can be done only with the assistance of a comparison microscope.

Modern fi rearms identifi cation began with the develop- ment and use of the comparison microscope. This instrument is the fi rearms examiner’s most important tool. The test and evidence bullets are mounted on cylindrical adjustable holders beneath the objective lenses of the microscope, each pointing in the same direction (see Figure 11 ). Both bullets are observed simultaneously within the same fi eld of view, and the examiner rotates one bullet until a well-defi ned land or groove comes into view.

Once the striation markings are located, the other bullet is rotated until a matching region is found. Not only must the lands and grooves of the test and evidence bullet have identical widths, but the longitudinal striations on each must coincide. When a matching area is located, the two bullets are simultaneously ro- tated to obtain additional matching areas around the periphery of the bullets. Figure 12 shows a typical photomicrograph of a bullet match as viewed under a comparison microscope.

CONSIDERATIONS IN BULLET COMPARISON Unfortunately, the fi re- arms examiner rarely encounters a perfect match all around the

FIGURE 11 A bullet holder beneath the objective lens of a comparison microscope. Courtesy Leica Microsystems, Buffalo, NY, www.leica-microsystems.com

FIGURE 12 A photomicrograph of two bullets through a comparison microscope. The test bullet is on the right; the questioned bullet is on the left. Courtesy Philadelphia Police Department Laboratory

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FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

bullet’s periphery. The presence of grit and rust can alter the markings on bul- lets fi red through the same barrel. More commonly, recovered evidence bul- lets become so mutilated and distorted on impact that they yield only a small area with intact markings.

Furthermore, striation markings on a barrel are not permanent structures; they are subject to continuing alteration through wear as succeeding bullets traverse the length of the barrel. Fortunately, these changes are usually not dra- matic and do not prevent the matching of two bullets fi red by the same weapon. As with fi ngerprint comparison, there are no hard-and-fast rules governing the minimum number of points required for a bullet comparison. The fi nal opinion must be based on the judgment, experience, and knowledge of the expert.

Frequently, the fi rearms examiner receives a spent bullet without an accompanying suspect weapon and is asked to determine the caliber and possible make of the weapon. If a bullet appears not to have lost any metal, its weight may be one factor in determining its caliber. In some instances, the number of lands and grooves, the direction of twist, and the widths of lands and grooves are useful class characteristics for eliminating certain makes of weap- ons from consideration. For example, a bullet that has fi ve lands and grooves and twists to the right could not have come from a weapon manufactured by Colt because Colts are not manufactured with these class characteristics.

Sometimes a bullet has rifl ing marks that set the weapon it was fi red from apart from most other manufactured weapons, as is the case with Marlin rifl es. These weapons are rifl ed by a technique known as microgrooving and may have eight to twenty-four grooves impressed into their barrels; few other weapons are manufactured in this fashion. For this reason, the FBI maintains a record known as the General Rifl ing Characteristics File. This fi le contains listings of class characteristics, such as land- and groove-width measure- ments, for known weapons. It is periodically updated and distributed to the law enforcement community to help identify rifl ed weapons from retrieved bullets.

Unlike rifl ed fi rearms, a shotgun has a smooth barrel, so projectiles pass- ing through a shotgun barrel are not impressed with any characteristic mark- ings that can be related back to the weapon later. Shotguns generally fi re small lead balls or pellets contained within a shotgun shell (see Figure 13 ). A paper or plastic wad pushes the pellets through the barrel when the shell’s powder charge is ignited. By weighing and measuring the diameter of the shot recovered at a crime scene, the examiner can usually determine the size of shot used in the shell. The size and shape of the recovered wad may also reveal the gauge of the shotgun used and, in some instances, may indicate the manufacturer of the fi red shell.

Priming mixture

Battery cup

Primer

Anvil

Base wad

Flash hole Metal head

Smokeless powder

Wad

Plastic body

Crimp

Shot

FIGURE 13 A cross-section of a loaded shotgun shell.

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FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

CLOSER ANALYSIS THE COMPARISON MICROSCOPE

Forensic microscopy often requires a side-by-side comparison of specimens. This kind of examination can best be performed with a comparison microscope, such as the one pictured in the fi gure.

Basically, the comparison microscope is two compound micro- scopes combined into one unit. The unique feature of its design is that it uses a bridge incorporating a series of mirrors and lenses to join two independent objective lenses into a single binocular unit. A viewer looking through the eyepiece lenses of the comparison micro- scope observes a circular fi eld equally divided into two parts by a fi ne line. The specimen mounted under the left-hand objective appears in the left half of the fi eld, and the specimen under the right-hand objective appears in the right half of the fi eld. It is important to closely match the optical characteristics of the objective lenses to ensure that both specimens are seen at equal magnifi cation and with minimal but identical lens distortions. Comparison microscopes designed to compare opaque objects, such as bullets and cartridges, are equipped with vertical or refl ected illumination. Comparison microscopes used to compare hairs or fi bers use transmitted illumination.

Figure 12 shows the striation markings on two bullets that have been placed under the objective lenses of a comparison microscope. Modern fi rearms examination began with the introduction of the comparison microscope, which gives the fi rearms examiner a side- by-side, magnifi ed view of two bullets. Bullets that are fi red through the same rifl e barrel display comparable rifl ing markings on their surfaces. Matching the majority of striations present on each bullet justifi es a conclusion that both bullets traveled through the same barrel. The comparison microscope—two independent objective lenses joined

together by an optical bridge. Courtesy Leica Microsystems, Buffalo, NY, www.leica-microsystems.com

gauge The size designation of a shotgun; originally the number of lead balls with the same diameter as the barrel that would make a pound. The only exception is the .410 shotgun, in which bore size is 0.41 inch.

breech face mark The rear part of a fi rearm barrel.

The diameter of the shotgun barrel is expressed in terms of its gauge . 1 The higher the gauge number, the smaller the barrel’s diameter. For example, a 12-gauge shotgun has a bore diameter of 0.730 inch, and a 16-gauge shot- gun has an interior diameter of 0.670 inch. The exception to this rule is the .410-gauge shotgun, whose gauge number refers directly to the barrel’s bore measurement of 0.41 inch in diameter.

CARTRIDGE CASES

The act of pulling a trigger releases the weapon’s fi ring pin, causing it to strike the primer, which in turn ignites the powder. The expanding gases generated by the burning gunpowder propel the bullet forward through the barrel, si- multaneously pushing the spent cartridge case or shell back with equal force against the breech face mark . As the bullet is marked by its passage through the barrel, the shell is also impressed with markings by its contact with the metal surfaces of the weapon’s fi ring and loading mechanisms. As with bul- lets, these markings can be reproduced in test-fi red cartridges to provide

203

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

distinctive points of comparison for individualizing a spent shell to a rifl ed weapon or shotgun.

The cup of the fi ring pin is impressed into the relatively soft metal of the primer on the cartridge case, revealing the minute distortions of the fi ring pin. These imperfections may be suffi ciently random to individualize the pin impression to a single weapon. Similarly, the cartridge case, in its rearward thrust, is impressed with the surface markings of the breech face mark. The breech face mark, like any machined surface, is populated with random stria- tion markings that become a highly distinctive signature for individualizing its surface.

Other distinctive markings that may appear on the brass portions of shells as a result of metal-to-metal contact are caused by the extractor and ejector mechanism and the magazine, or clip, as well as by imperfections on the fi ring chamber walls. The photomicrographs in Figure 14 reveal a com- parison of the fi ring pin and breech face mark impressions on evidence and test-fi red shells.

These impressions provide points for individualizing the shell to a weapon that are just as valuable as cartridge cases discharged from a rifl ed fi rearm. Furthermore, in the absence of a suspect weapon, the size and shape of a

WebExtra 2

3-D Shotgun Shell Illustrations www.mycrimekit.com

WebExtra 3

3-D Revolver Cartridge Illustrations www.mycrimekit.com

extractor The mechanism in a fi rearm that withdraws a cartridge or fi red case from the chamber.

ejector The mechanism in a fi rearm that throws the cartridge or fi red case from the fi rearm.

CASEFILES SACCO AND VANZETTI

In 1920, two security guards were viciously gunned down by uniden- tifi ed assailants. The security guards were transporting shoe factory payrolls, nearly $16,000 in cash, at the time of the robbery-murder. Eyewitnesses described the assailants as “Italian-looking,” one with a full handlebar moustache. The robbers had used two fi rearms that left behind three different brands of shells.

Two suspects were identifi ed and arrested: Nicola Sacco and his friend, the amply mustachioed Bartolomeo Vanzetti. After denying owning any fi rearms, each was found to be in possession of a loaded pistol. In fact, Sacco’s pistol was .32 caliber, the same caliber as the crime-scene bullets. In Sacco’s pockets were found twenty-three bullets matching the brands of the empty shells found at the murder scene.

This case coincided with the “Red Scare,” a politically turbu- lent time in post–World War I America. Citizens feared socialist zeal- ots, and the media played up these emotions. Political maneuvering and the use of the media muddied the waters surrounding the case, and the fact that both suspects belonged to anarchist political groups that advocated revolutionary violence against the government only incited public animosity toward them. Sympathetic socialist organi- zations attempted to turn Sacco and Vanzetti into martyrs, calling their prosecution a “witch hunt.”

The outcome of the trial ultimately depended on whether the prosecution could prove that Sacco’s pistol fi red the bullets that killed the two security guards. At trial, the ballistics experts testifi ed that the bullets used were no longer in production, and they could not fi nd similar ammunition to use in test fi rings—aside from the unused cartridges found in Sacco’s pockets. A forensics expert for the prosecution concluded that a visual examination showed that the bullets matched, leading the jury to return a verdict of guilty. Sacco and Vanzetti were sentenced to death.

Because of continued public protests, a committee was appointed in 1927 to review the case. Around this time, Calvin Goddard, at the Bureau of Forensic Ballistics in New York, perfected the comparison microscope for use in forensic fi rearms investigations. The committee asked Goddard to examine the bullets in question. A test-fi red bullet from Sacco’s weapon was matched conclusively by Goddard to one of the crime-scene bullets. The fates of Sacco and Vanzetti were sealed, and they were put to death in 1927.

CORBIS-NY

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FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

fi ring pin impression and/or the position of ejector marks in relationship to extractor and other markings may provide some clue to the type or make of the weapon that fi red the questioned shell, or at least eliminate a large number of possibilities.

Quick Review • The manufacture of a gun barrel requires impressing its inner surface with

spiral grooves, a step known as rifl ing. Rifl ing imparts spin to the projec- tile when it is fi red, which keeps it on an accurate course.

• No two rifl ed barrels have identical striation markings. These striations form the individual characteristics of the barrel. The inner surface of the barrel of a gun transfers its striation markings to bullets that pass through it.

• The class characteristics of a rifl ed barrel include the number of lands and grooves and the width and direction of twist.

• The comparison microscope is a fi rearms examiner’s most important tool because it allows two bullets to be compared simultaneously.

• The fi ring pin, breech face mark, and ejector and extractor mechanism also offer a highly distinctive signature for individualization of cartridge cases.

• Unlike handguns, a shotgun is not rifl ed—it has a smooth barrel. Because of this, shotgun shells are not impressed with any characteristic rifl ing striation markings that can be used to compare two shotgun shells to determine whether they were fi red from the same weapon.

Automated Firearms Search Systems The use of fi rearms, especially semiautomatic weapons, during the commission of a crime has signifi cantly increased throughout the United States. Because of the expense of such fi rearms, the likelihood that a specifi c weapon will be used in multiple crimes has risen. The advent of computerized imaging tech- nology has made it possible to store bullet and cartridge surface characteris- tics in a manner analogous to automated fi ngerprint fi les. Using this concept, crime laboratories can be networked, allowing them to share information on bullets and cartridges retrieved from several jurisdictions.

WebExtra 4

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WebExtra 5

3-D Rifl e Cartridge Illustrations www.mycrimekit.com

WebExtra 6

View Animations to Illustrate the Firing Process and the Extraction/Ejection Process of a Semiautomatic Pistol www.mycrimekit.com

FIGURE 14 A comparison microscope photomicrograph showing a match between (a) fi ring pin impres- sions and (b) the breech face mark on two shells. Courtesy Ronald Welsh, Bureau of Forensic Services, Central Valley Laboratory, Ripon, CA

(a) (b)

205

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

EARLY SYSTEMS

The effort to build a national computerized database for fi rearms evidence in the United States had a rather confusing and ineffi cient start in the early 1990s. Two major federal law enforcement agencies, the FBI and the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), offered the law enforce- ment community competing and incompatible computerized systems.

The automated search system developed for the FBI was known as DRUG- FIRE . This system emphasized the examination of unique markings on the car- tridge casings expended by the weapon. The specimen was analyzed through a microscope attached to a video camera. The magnifi cation allowed for a close-up view to identify individual characteristics. The image was captured by the video camera, digitized, and stored in a database. Although DRUGFIRE emphasized cartridge-case imagery, the images of highly characteristic bullet striations could also be stored in a like manner for conducting comparisons.

The Integrated Ballistic Identifi cation System (IBIS), developed for the Bureau of Alcohol, Tobacco, Firearms, and Explosives, processed digital microscopic images of identifying features found on both expended bullets and cartridge cas- ings. IBIS incorporated two software programs: Bulletproof, a bullet- analyzing module, and Brasscatcher, a cartridge-case-analyzing module. A schematic dia- gram of Bulletproof’s operation is depicted in Figure 15 .

Processor

Database

High-resolution monitor

Modem

System monitor

Input devices

Printer

Specimen manipulator

System input/output configuration

Microscope

Video camera

Image digitizer

FIGURE 15 Bulletproof confi guration. The sample is mounted on the specimen manipulator and illuminated by the light source from a microscope. The image is captured by a video camera and digitized. This digital image is then stored in a database, available for retrieval and comparison. The search for a match includes analyzing the width of land and groove impressions along with both rifl ing and individual characteristics. The Brasscatcher software uses the same system confi guration but emphasizes the analysis of expended cartridge casings rather than the expended bullets. Courtesy Forensic Technology (WAI) Inc., Côte St-Luc, Quebec, Canada

206

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

NIBIN In 1999, members of the FBI and ATF joined forces to introduce the National Integrated Ballistics Information Network (NIBIN) program to the dis- cipline of fi rearms examination. The new, unifi ed system incorporates both DRUGFIRE and IBIS technologies. ATF has overall responsibility for the sys- tem sites, and the FBI is responsible for the communications network.

Agencies using the new NIBIN technology produce database fi les from bullets and cartridge casings retrieved from crime scenes or test fi res from retrieved fi rearms. More than two hundred law enforcement agencies world- wide have adapted this technology. The success of the system has been proved: With more than 1.6 million images compiled nationwide, law enforcement agencies have connected more than 34,000 bullets and casings to more than one crime (see Figure 16 ).

FIGURE 16 Bullets A, B, C, and D were acquired by the IBIS database at different times from different crime scenes. D is a fragmented bullet that had only three land impressions available for acquisition. On entering bullet D, IBIS found a potential matching candidate in the database: B. On the far right, bullet D is compared to bullet B using the IBIS imaging software. Finally, a forensic fi rearms examiner using the actual evidence under a conventional comparison microscope will confi rm the match between B and D. Courtesy Forensic Technology (WAI) Inc., Côte St-Luc, Quebec, Canada

207

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

For example, in a recent case, a robbery-turned-double-homicide left two store clerks dead. Two bullets and two .40-caliber Smith & Wesson cartridge casings were recovered. Later that day, a Houston security guard was shot and killed during a botched armed robbery. A bullet and .40-caliber Smith & Wesson cartridge casing were recovered and entered into NIBIN. Once these were processed, a correlation was found between the murder of the security offi cer and a separate aggravated robbery that had occurred two weeks ear- lier. All three crimes were linked with a fi rearm believed to be a .40-caliber Smith & Wesson pistol.

Further investigation into the use of a victim’s credit card helped police locate two suspects. In the possession of one suspect was a .40-caliber Smith & Wesson pistol. The gun was test-fi red and imaged into NIBIN. The casing from the test-fi red weapon matched the evidence obtained in the robbery and the aggravated robbery-homicides. A fi rearms examiner verifi ed the associations by traditional comparisons. Before this computerized technology existed, it would have taken years—or it may have been impossible—to link all of these shootings to a single fi rearm.

In another example, the ATF laboratory in Rockville, Maryland, received 1,466 cartridge casings from the Ovcara mass burial site in Bosnia. After pro- cessing and imaging profi les for all casings, the examiners determined that eighteen different fi rearms had been used at the site. With the help of NIBIN technology and competent examiners, jurists attempted to convict an indi- vidual for war crimes.

NIBIN serves only as a screening tool for fi rearms evidence. A computer- ized system does not replace the skills of the fi rearms examiner. NIBIN can screen hundreds of unsolved fi rearms cases and may narrow the possibilities to several fi rearms. However, the fi nal comparison will be made by a forensic examiner through traditional microscopic methods.

BALLISTIC FINGERPRINTING

Participating crime laboratories in the United States are building databases of bullet and cartridge cases found at crime scenes and those fi red in tests of guns seized from criminals. As these databases prove their usefulness in solving crimes, law enforcement offi cials and the political community are scrutinizing the feasibility of scaling this concept up to create a system of ballistic fi nger- printing. This system would entail the capture and storage of appropriate markings on bullets and cartridges test-fi red from handguns and rifl es before they are sold to the public. Questions regarding who will be responsible for collecting the images and details of how will they be stored are but two of many issues to be decided. The concept of ballistic fi ngerprinting is an intrigu- ing one for the law enforcement community and promises to be explored and debated intensely in the future.

Quick Review • The advent of computerized imaging technology has made possible the

storage of bullet and cartridge surface characteristics in a manner analo- gous to automated fi ngerprint fi les.

• Two automated fi rearms search systems are DRUGFIRE, developed by the FBI, and IBIS, developed by the ATF.

• NIBIN is the National Integrated Ballistics Information Network, a unifi ed fi rearms search system that incorporates both DRUGFIRE and IBIS technologies.

208

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

Gunpowder Residues Modern ammunition is propelled toward a target by the expanding gases created by the ignition of smokeless powder or nitrocellulose in a cartridge. Under ideal circumstances, all of the powder is consumed in the process and converted into the rapidly expanding gases. However, in practice the powder is never totally burned. When a fi rearm is discharged, unburned and partially burned particles of gunpowder in addition to smoke are propelled out of the barrel, along with the bullet, toward the target. If the muzzle of the weapon is suffi ciently close, these products are deposited onto the target. The distribu- tion of gunpowder particles and other discharge residues around the bullet hole permits a distance determination , an assessment of the distance from which a handgun or rifl e was fi red.

DISTANCE DETERMINATION

In incidents involving gunshot wounds, it is often necessary to determine the distance from which the weapon was fi red. For example, in incidents involving a shooting death, the suspect often pleads self-defense as the motive for the attack. Such claims are fertile grounds for distance determinations because fi nding the proximity of the people involved is necessary to establish the facts of the incident. Similarly, careful examination of the gunshot wounds of suicide victims usually reveals characteristics associated with a very close-range shot. The absence of such characteristics strongly indicates that the wound was not self-infl icted and signals the possibility of foul play.

The accuracy of a distance determination varies according to the circum- stances of the case. When the investigator is unable to recover a suspect weapon, the best the examiner can do is to state whether a shot could have been fi red a given distance from the target. More exact opinions are possible only when the examiner has the suspect weapon in hand and knows the type of ammunition used in the shooting.

HANDGUNS AND RIFLES The precise distance from which a handgun or ri- fl e has been fi red must be determined by carefully comparing the powder residue pattern on the victim’s clothing or skin to test patterns made by fi ring the  suspect weapon at varying distances from a target. A white cloth or a fabric comparable to the victim’s clothing may be used as a test target (see Figure 17 ). Because the spread and density of the residue pattern vary widely among weap- ons and ammunition, such a comparison is signifi cant only when it is made with the suspect weapon and suspect ammunition, or with ammunition of the same type and make. By comparing the test and evidence patterns, the examiner may fi nd enough similarity in shape and density by which to judge the distance from which the shot was fi red.

Without the weapon, the examiner is restricted to looking for recogniz- able characteristics around the bullet hole. Such fi ndings are at best approxi- mations made as a result of general observations and based on the examiner’s experience. However, some noticeable characteristics should be sought. For instance, when the weapon is held in contact with or less than 1 inch from the target, a heavy concentration of residue from smokelike vaporous lead usually surrounds the bullet’s entrance hole. Often, loose fi bers surrounding a contact hole show scorch marks from the fl ame discharge of the weapon, and some synthetic fi bers may show signs of being melted as a result of the heat from the discharge. Furthermore, the blowback of muzzle gases may produce a stellate (i.e., star-shaped) tear pattern around the hole. Such a hole is invariably surrounded by a rim of a smokelike deposit of vaporous lead (see Figure 18 ).

distance determination The process of determining the distance between the fi rearm and a target, usually based on the distribution of powder patterns or the spread of a shot pattern.

209

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

A halo of vaporous lead deposited around a bullet hole normally indicates the bullet was discharged 18 inches or less from the target. The presence of scattered specks of unburned and partially burned powder grains without any accompanying soot can often be observed at distances up to approximately 25 inches. Occasionally, however, scattered gunpowder particles are noted at a fi ring distance as far out as 36 inches. A weapon that has been fi red more than 3 feet from a target usually does not deposit any powder residues on the target’s sur- face. (However, with ball powder ammunition, this distance may be extended to 8 feet.)

When a weapon has been fi red from 3  feet or more away, the only visual indication that the hole was made by a bullet is a dark ring, known as bullet wipe, around the perimeter of the entrance hole. Bullet wipe consists of a mixture of carbon, dirt, lubricant, primer residue, and lead wiped off the bullet’s surface as it passes

through the target. Again, in the absence of a suspect weapon, these observa- tions are only general guidelines for estimating target distances. Numerous factors—barrel length, caliber, type of ammunition, and type and condition

(b)

(c) (d)

(a)

FIGURE 17 Test powder patterns made with a Glock 9mm luger fi red at the following distances: (a) contact, (b) 6 inches, (c) 12 inches, and (d) 18 inches. Michelle D. Miranda

FIGURE 18 A contact shot. Michelle D. Miranda

210

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

of the weapon fi red—infl uence the amount of gunpowder residue deposited on a target.

SHOTGUNS The determination of fi ring distances involving shotguns must also be related to test fi rings performed with the suspect weapon using the same type of ammunition known to be used in the crime. In the absence of a weapon, the muzzle-to-target distance can be estimated by measuring the spread of the dis- charged shot. With close-range shots varying in distance up to 5 feet, the shot charge enters the target as a concentrated mass, producing a hole somewhat larger than the bore of the barrel. As the distance increases, the pellets progres- sively separate and spread out. Generally speaking, the spread in the pattern made by a 12-gauge shotgun increases 1 inch for each yard of distance. Thus, a 10-inch pattern would be produced at approximately 10 yards. Of course, this is only a rule of thumb; normally, many variables can affect the shot pattern.

Other factors include the barrel length, the size and quantity of the pellets fi red, the quantity of powder charge used to propel the pellets, and the choke of the gun under examination. Choke is the degree of constriction placed at the muzzle end of the barrel. The greater the choke, the narrower the shotgun pattern and the faster and farther the pellets will travel.

POWDER RESIDUES ON GARMENTS

When garments or other evidence relevant to a shooting are received in the crime laboratory, the surfaces of all items are fi rst examined microscopically for gunpowder residue. These particles may be identifi able by their characteristic colors, sizes, and shapes. However, the absence of visual indications does not preclude the possibility that gunpowder residue is present. Sometimes the lack of color contrast between the powder and garment or the presence of heavily encrusted deposits of blood can obscure the visual detection of gunpowder. Often, an infrared photograph of the suspect area overcomes the problem. Such a photograph may enhance the visual color contrast, thus revealing vaporous lead and powder particles deposited around the hole (see Figure  19 ).

choke An interior constriction placed at or near the muzzle end of a shotgun’s barrel to control shot dispersion.

(a) (b)

FIGURE 19 (a) A shirt bearing a powder stain, photographed under normal light. (b) An infrared photo- graph of the same shirt.

211

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

In other situations, this may not help, and the analyst must use chemical tests to detect gunpowder residues.

Nitrites are one type of chemical product that results from the incomplete combustion of smokeless (nitrocellulose) powder. One test method for locating powder residues involves transferring particles embedded on the target surface to chemically treated gelatin-coated photographic paper. This procedure is known as the Greiss test . The examiner presses the photographic paper onto the target with a hot iron; once the nitrite particles are on the paper, they are made easily visible through chemical treatment. In addition, comparing the developed nitrite pattern to nitrite patterns obtained from test fi rings at known distances can be useful in determining the shooting distance from the target. A second chemical test is then performed to detect any trace of lead residue around the bullet hole. The questioned surface is sprayed with a solution of sodium rhodizonate, followed by a series of oversprays of acid solutions. This treatment turns lead particles pink then blue-violet.

Quick Review • The distribution of gunpowder particles and other discharge residues

around a bullet hole permits an assessment of the distance from which a handgun or rifl e was fi red.

• The precise distance from which a handgun or rifl e was fi red is deter- mined by carefully comparing the powder residue pattern on the victim’s clothing to test patterns made when the suspect weapon is fi red at varying distances from a target.

• The Greiss test is a chemical test used to examine patterns of gunpowder residues around bullet holes. It tests for the presence of nitrates.

Primer Residues on the Hands The fi ring of a weapon not only propels residues toward the target, but it also blows gunpowder and primer residues back toward the shooter (see Figure  20 ). As a result, traces of these residues are often deposited on the fi ring hand of the shooter, and their detection can provide valuable informa- tion about whether an individual has recently fi red a weapon.

DETECTING PRIMER RESIDUES

Early efforts at demonstrating powder residues on the hands centered on chemical tests that could detect unburned gunpowder or nitrates. For many years, the dermal nitrate test was popular. It required the application of hot paraffi n or wax to the suspect’s hand with a paintbrush. After drying into a solid crust, the paraffi n was removed and tested with diphenylamine. A blue color indicated a positive reaction for nitrates. However, the dermal nitrate test has fallen into disfavor with law enforcement agencies, owing mainly to its lack of specifi city. Common materials such as fertilizers, cosmetics, urine, and tobacco all give positive reactions that are indistinguishable from that obtained for gunpowder by this test.

Efforts to identify a shooter now center on the detection of primer residues deposited on the hand of a shooter at the time of fi ring. With the exception of those in most .22-caliber ammunition, primers currently manufactured con- tain a blend of lead styphnate, barium nitrate, and antimony sulfi de. Residues from these materials are most likely to be deposited on the thumb web and

Greiss test A chemical test used to examine patterns of gunpowder residues around bullet holes.

212

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

the back of the fi ring hand of a shooter because these areas are closest to gases escaping along the side or back of the gun during discharge. In ad- dition, individuals who handle a gun without fi ring it may have primer resi- dues deposited on the palm of the hand where it has been in contact with the weapon.

However, with the handling of a used fi rearm, the passage of time, and the resumption of normal activities following a shooting, gunshot residues from the back of the hand are frequently redistributed to other areas, including the palms. Therefore, it is not unusual to fi nd higher levels of barium and antimony on the palms than on the backs of the hands of known shooters. Another possibility is the deposition of signifi cant levels of barium and antimony on the hands of an individual who is near a fi rearm when it is discharged.

TESTS FOR PRIMER RESIDUES

The determination of whether a person has fi red or handled a weapon or has been near a discharged fi rearm is normally made by measuring the presence and possibly the amount of barium and antimony on the relevant portions of the suspect’s hands. A variety of materials and techniques are used for removing these residues. The most popular approach, and certainly the most convenient for the fi eld investigator, is to apply an adhesive tape or adhesive to the hand’s surface to remove any adhering residue particles.

SWABBING Another approach is to remove any residues present by swabbing both the fi ring and nonfi ring hands with cotton that has been moistened with 5 percent nitric acid. The front and back of each hand are swabbed separately. All four swabs, along with a moistened control, are then forwarded to the crime laboratory for analysis.

In any case, once the hands are treated for the collection of barium and antimony, the collection medium must be analyzed for the presence of these

FIGURE 20 When a handgun is fi red, gunpowder and primer residues are normally blown back toward the hand of the shooter. Courtesy Forensic Technology WAI Inc.

213

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

elements. High barium and antimony levels on the suspect’s hand(s) strongly indicate that the person fi red or handled a weapon or was near a fi rearm when it was discharged. Because these elements are normally present in small quantities (e.g., less than 10 micrograms) after a fi ring, only the most sensitive analytical techniques can be used to detect them.

Unfortunately, even though most speci- mens submitted for this type of analysis have been obtained from individuals strongly sus- pected of having fi red a gun, there has been a low rate of positive fi ndings. The major diffi culty appears to be the short time that primer residues remain on the hands. These residues are readily removed by intentional or unintentional washing, rubbing, or wiping of the hands. In fact, one study demonstrated that it is very diffi cult to detect primer resi-

dues on cotton hand swabs taken just two hours after fi ring a weapon. 2 Hence, some laboratories do not accept cotton hand swabs taken from living people six or more hours after a fi ring has occurred.

In cases that involve suicide victims, a higher rate of positive fi ndings for the presence of gunshot residue is obtained when the hand swabbing is conducted before the person’s body is moved or when the hands are protected by paper bags. 3 However, hand swabbing or the application of an adhesive cannot be used to detect fi rings of most .22-caliber rim-fi re ammunition. Such ammuni- tion’s primer may contain only barium or neither barium nor antimony.

SEM TESTING Most laboratories that can detect gunshot residue require application of an adhesive to the shooter’s hands Microscopic primer and gunpowder particles on the adhesive are then found with a scanning electron microscope (SEM). The characteristic size and shape of these particles distin- guishes them from other contaminants on the hands (see Figure 21 ). When the SEM is linked to an X-ray analyzer, an elemental analysis of the particles can be conducted. A fi nding of a select combination of elements (i.e., lead, bar- ium, and antimony) confi rms that the particles are indeed primer residue (see Figure 22 ).

The major advantage of the SEM approach for primer residue detection is its enhanced specifi city over hand swabbing. The SEM characterizes primer particles by their size and shape as well as by their chemical composition. Unfortunately, the excessive operator time required to fi nd and characterize gunshot residue has discouraged the use of this technique. The availability of automated particle search and identifi cation systems for use with scanning electron microscopes may overcome this problem. Results of work performed with automated systems show that it is signifi cantly faster than a manual ap- proach for fi nding gunshot residue particles. 4

Quick Review • Firing a weapon propels residues toward the target and blows gunpowder

and primer residues back toward the shooter. Traces of these residues are often deposited on the fi ring hand of the shooter, providing valuable infor- mation about whether an individual has recently fi red a weapon.

FIGURE 21 An SEM view of gunshot residue particles. Courtesy Foster and Freeman Limited, Worchester Shine, U.K., www.fosterfreeman.co.uk

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FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

FIGURE 22 A spectrum showing the presence of lead, barium, and antimony in gunshot residue. Jeol USA Inc.

4

3

2

1

0 2 4 6 8 10 12 14 16 18 20

Range (ke V)

Pb Counts [x10]

Pb

Sb Sb

Ba

Ba

Ba

Pb

Pb

Pb

• Examiners measure the amount of barium and antimony on the relevant portion of the suspect’s hands or characterize the morphology of particles containing these elements to determine whether a person has fi red or han- dled a weapon or was near a discharged fi rearm.

Serial Number Restoration Today, many manufactured items, including automobile engine blocks and fi rearms, are impressed with serial numbers for identifi cation. Increasingly, the criminalist must restore such numbers when they have been removed or obliterated by grinding, rifl ing, or punching.

Serial numbers are usually stamped, on a metal body or frame or on a metal plate, with hard steel dies. These dies strike the metal surface with a force that allows each digit to sink into the metal at a prescribed depth. Serial numbers can be restored because the metal crystals in the stamped zone are placed under a permanent strain that extends a bit beneath the original numbers. When a suitable etching agent is applied, the strained area dissolves faster than the unaltered metal, thus revealing the etched pattern in the form of the original numbers (see Figure 23 ). However, if the zone of strain has been removed, or if the area has been impressed with a different strain pattern, the number usually cannot be restored.

Before any treatment with the etching reagent, the obliterated surface must be thoroughly cleaned of dirt and oil and polished to a mirrorlike fi nish. The reagent is swabbed onto the surface with a cotton ball. The choice of

215

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

CLOSER ANALYSIS THE SCANNING ELECTRON MICROSCOPE (SEM)

The scanning electron microscope (SEM) creates an image by aiming a beam of electrons at a specimen, then the electron emissions from the specimen are studied on a closed-circuit TV (see Figure 1). This is accomplished by using electromagnetic focusing to direct electrons emitted by a hot tungsten fi lament onto the surface of the specimen. This primary electron beam causes the elements that make up the upper layers of the specimen to emit electrons known as second- ary electrons. About 20 to 30 percent of the primary electrons re- bound off the surface of the specimen. These electrons are known as backscattered electrons. The emitted electrons (both secondary and backscattered) are collected, and the amplifi ed signal is displayed on a cathode-ray, or TV, tube. By scanning the primary electron beam across the specimen’s surface in synchronization with the cathode- ray tube, the SEM converts the emitted electrons into an image of the specimen that displays on the cathode-ray tube.

The major attractions of the SEM image are its high magnifi ca- tion, high resolution, and great depth of focus. In its usual mode, the SEM has a magnifi cation that ranges from 10� to 100,000�. Its depth of focus is 300 times better than that of optical systems at similar magnifi cations, and the resultant picture is almost stereo- scopic in appearance. Its great depth of fi eld and magnifi cation are exemplifi ed in the magnifi ed cystolithic hair on the marijuana leaf shown in Figure 2. A SEM image of a vehicle’s headlight fi laments may reveal whether the headlights were on or off at the time of a collision (see Figures 3 and 4).

FIGURE 1 A scanning electron microscope. Jeol USA Inc.

FIGURE 2 The cystolithic hairs of the marijuana leaf, as viewed with a scanning electron microscope (800x). Courtesy Jeff Albright

FIGURE 3 The melted ends of a hot fi lament break indicate that the headlights were on when an accident occurred. Jeol USA Inc.

(continued )

216

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

FIGURE 4 The sharp ends of a cold fi lament break indicate that the headlights were off when an accident occurred. Courtesy, Foster and Freeman Limited, Worchester Shine, U.K., www.fosterfreeman.co.uk

ELECTRON GUN

DEFLECTION SYSTEM

FOCUSED BEAM OF ELECTRONS

SAMPLE OF GUNSHOT RESIDUE

DISPLAY

SECONDARY ELECTRONS

X-RAYS

ELECTRON VOLTS X 10–3 01 05 10

IN TE

N SI

TY

DISPLAY

IMAGE PROCESSOR

X-RAY ANALYZER

Pb

Pb

Sb

Ba

Ba

FIGURE 5 A schematic diagram of a scanning electron microscope displaying the image of a gun- shot residue particle. Simultaneously, an X-ray analyzer detects and displays X-ray emissions from the elements lead (Pb), antimony (Sb), and barium (Ba) present in the particle.

CLOSER ANALYSIS (continued)

Another facet of scanning electron microscopy is the use of X-ray production to determine the elemental composition of a specimen. X-rays are generated when the electron beam of the scanning electron microscope strikes a target. When the SEM is coupled with an X-ray analyzer, the emitted X-rays can be sorted according to their energy values and used to build a picture of the elemental distribu- tion in the specimen. Because each element emits X-rays of charac- teristic energy values, the X-ray analyzer can identify the elements present in a specimen. Furthermore, the elemental concentration can be determined by measuring the intensity of the X-ray emission.

As shown in Figure 5, when a sample of gunshot residue collected off the hands of a suspect shooter is exposed to a beam of electrons from the scanning electron microscope, X-rays are emitted. These X-rays are passed into a detector, where they are converted into electrical signals. These signals are sorted and displayed according to the energies of the emitted X-rays. Through the use of this technique, the elements lead, antimony, and barium, frequently found in most primers, can be rapidly detected and identifi ed.

217

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

etching reagent depends on the type of metal surface being worked on. A solution of hydrochloric acid (120 milliliters), copper chloride (90 grams), and water (100 milliliters) generally works well for steel surfaces.

Collection and Preservation of Firearms Evidence FIREARMS

The Hollywood technique of picking up a weapon by its barrel with a pencil or stick in order to protect fi ngerprints must be avoided. This practice only disturbs powder deposits, rust, or dirt lodged in the barrel, and consequently may alter the striation markings on test-fi red bullets. If recovery of latent fi ngerprints is a primary concern, the investigator should hold the weapon by the edge of the trigger guard or by the checkered portion of the grip, which usually does not retain identifi able fi ngerprints.

The most important consideration in handling a weapon is safety. Before any weapon is sent to the laboratory, all precautions must be taken to prevent an accidental discharge of a loaded weapon in transit. In most cases, it will be necessary to unload the weapon. If this is done, fi rst a record should be made of the weapon’s hammer and safety position; likewise, the location of all fi red and unfi red ammunition in the weapon must be recorded.

When a revolver is recovered, the chamber position should be indicated by a scratch mark on the cylinder where it aligns with the barrel. Each chamber is designated a number on a diagram, and as each cartridge or casing is removed, it should be marked to correspond to the number of its

FIGURE 23 Obliterated or altered serial numbers on fi rearms can be restored by analysts using chemical means. Federal Bureau of Investigation

218

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

corresponding chamber in the diagram. Knowledge of the cylinder position of a cartridge casing may be useful for later determination of the sequence of events, particularly in shooting cases, when more than one shot was fi red. Each round should be placed in a separate box or envelope. If the weapon is an automatic, the magazine must be removed and checked for prints and the chamber then emptied.

As with any other type of physical evidence recovered at a crime scene, fi rearms evidence must be marked for identifi cation, and a chain of custody must be established. When a fi rearm is recovered, an identifi cation tag should be attached to the trigger guard. The tag should include appropriate identi- fying data, including the weapon’s serial number, make, and model and the investigator’s initials.

When a weapon is recovered from an underwater location, no effort should be made to dry or clean it. Instead, the fi rearm should be transported to the laboratory in a receptacle containing enough of the same water to keep it submerged. This procedure prevents rust from developing during transport.

AMMUNITION

The protection of class and individual markings on bullets and cartridge cases must be the primary concern of the fi eld investigator. Thus, extreme caution is needed when removing a lodged bullet from a wall or other object. If the bullet’s surface is accidentally scratched during this operation, valuable striation markings could be obliterated. It is best to free bullets from their target by carefully breaking away the surrounding support material while avoiding direct contact with the projectile.

Bullets, cartridge casings, and discharged shells from shotguns should just be placed in a container that is appropriately marked for identifi cation. It is rec- ommended that the investigator not directly mark these items with a scribe. In any case, the investigator must protect the bullet by wrapping it in tissue paper before placing it in a pillbox or an evidence envelope for shipment to the crime laboratory. Minute traces of evidence such as paint and fi bers may be adhering to the bullet; the investigator must take care to leave these trace materials intact.

When semiautomatic or automatic weapons have been fi red, the ejection pattern of the casings can help establish the relationship of the suspect to the victim. For this reason, the investigator must note the exact location where a shell casing was recovered.

GUNPOWDER DEPOSITS

The clothing of a fi rearms victim must be carefully preserved to prevent damage or disruption to powder residues deposited around a bullet or shot hole. Cutting or tearing of clothing in the area of the holes must be avoided when removing the clothing. All wet clothing should be air-dried out of direct sunlight and then folded carefully to avoid disrupting the area around the bullet hole. Each item should be placed in a separate paper bag.

Quick Review • Criminalists can restore serial numbers removed or obliterated by grind-

ing, rifl ing, or punching. • Because the metal crystals in the stamped zone are placed under a per-

manent strain that extends a bit beneath the original numbers, the serial number can sometimes be restored through chemical etching.

• A suspect fi rearm should never be picked up by inserting an object into its barrel because this practice may alter the striation markings on test-fi red bullets.

219

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

• Before unloading a suspect weapon, the weapon’s hammer and safety po- sition should be recorded, as well as the locations of all fi red and unfi red ammunition in the weapon.

• The protection of class and individual markings on bullets and cartridge cases is the primary concern of the fi eld investigator when recovering bul- lets and cartridge casings.

Tool Marks A tool mark is any impression, cut, gouge, or abrasion caused by a tool coming into contact with another object. Most often, tool marks are encountered at burglary scenes that involve forcible entry into a building or safe. Generally, these marks occur as indented impressions into a softer surface or as abrasion marks caused by the tool cutting or sliding against another object.

COMPARING TOOL MARKS

Typically, an indented impression is left on the frame of a door or window as a result of the prying action of a screwdriver or crowbar. Careful examination of these impressions can reveal important class characteristics—that is, the size and shape of the tool. However, they rarely reveal any signifi cant individual characteristics that could permit the examiner to individualize the mark to a

single tool. Such characteristics, when they do exist, usually take the form of discernible random nicks and breaks that the tool has acquired through wear and use (see Figure 24 ).

Just as the machined surfaces of a fi rearm are impressed with random striations during its manufacture, the edges of a pry bar, chisel, screwdriver, knife, or cutting tool likewise display a series of microscopic irregularities that look like ridges and valleys. Such markings are created as a result of the machining processes used to cut and fi nish tools. The shape and pattern of such minute imperfections are further modifi ed by damage and wear during the life of the tool. Considering the variety of patterns that the hills and valleys can assume, it is highly unlikely that any two tools will be identical. Hence, these minute imperfections impart individ- uality to each tool.

If the edge of a tool is scraped against a softer surface, it may cut a series of striated lines that refl ect the pattern of the tool’s edge. With the aid of a comparison microscope, markings left in this manner can be compared in the laboratory with test tool marks made from the suspect tool. When a suffi cient number of striations match between the evidence and test markings, the result can be a positive comparison, and hence a defi nitive association of the tool with the evidence mark.

A major problem of tool mark comparisons is the diffi culty in duplicating in the laboratory the tool mark left at the crime scene. A thorough comparison requires preparing a series

of test marks by applying the suspect tool at various angles and pressures to a soft metal surface (lead is commonly used). This approach gives the examiner ample opportunities to duplicate many of the details of the original evidence marking. A photomicrograph of a typical tool mark comparison is illustrated in Figure 25 .

FIGURE 24 A comparison of a tool mark with a suspect screwdriver. Note how the presence of nicks and breaks on the tool’s edge helps individualize the tool to the mark.

220

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

COLLECTING TOOL MARK EVIDENCE

Whenever practical, the entire object or the part of the object bearing a tool mark should be submitted to the crime laboratory for examination. When removal of the tool mark is impractical, the only recourse is to photograph the marked area to scale and then make a cast of the mark. Liquid silicone casting material is best for reproducing most of the fi ne details of a mark (see Figure  26 ). However, even under the best conditions, the clarity of many of the tool mark’s minute details

FIGURE 25 A photograph of a tool mark comparison seen under a comparison microscope. Courtesy Leica Microsystems, Buffalo, NY, www.leica-microsystems.com

FIGURE 26 (a) Casting a tool mark impression with a silicone-based putty. (b) An impression alongside a suspect tool. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, NC, www.sirchie.com

(a) (b)

221

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

will be lost or obscured in a photograph or cast. Of course, this will reduce the chance of individualizing the mark to a single tool.

The crime-scene investigator must never attempt to fi t the suspect tool into the tool mark. Any contact between the tool and the marked surface may alter the mark and will, at the very least, raise serious questions about the integrity of the evidence. The suspect tool and mark must be packaged in separate containers, and every precaution must be taken to avoid contact between the tool and mark and another hard surface. Failure to protect the tool and mark from damage could result in the destruction of their individual characteristics.

Furthermore, the tool or its impression may contain valuable trace evi- dence. Chips of paint adhering to the mark or tool provide perhaps the best example of how the transfer of trace physical evidence can occur as a result of using a tool to gain forcible entry into a building. Obviously, the presence of trace evidence greatly enhances the evidential value of a tool or its mark. Preserving such evidence requires special care in handling and packaging to avoid loss or destruction.

Quick Review • The presence of minute imperfections on a tool imparts individuality to

that tool. The shape and pattern of such imperfections are further modi- fi ed by damage and wear during the life of the tool.

• The comparison microscope is used to compare crime-scene tool marks with test impressions made with the suspect tool.

Other Impressions From time to time, other types of impressions are left at a crime scene. This evidence may take the form of a shoe, tire, or fabric impression. It may be as varied as a shoe impression left on a piece of paper at the scene of a burglary ( Figure 27 ), a hit-and-run victim’s garment that has come into violent contact with an automobile ( Figure 28 ), or the impression of a bloody shoe print left on a fl oor or carpet at a homicide scene ( Figure 29 ).

PRESERVING IMPRESSIONS

The primary consideration in collecting impressions at the crime scene is the preservation of the impression or its reproduction for later examination in the crime laboratory. Before any impression is moved or otherwise handled, it must be photographed to show all the observable details of the impres- sion (a scale should be included in the picture). Several shots should be taken directly over the impression as well as at various angles around the impres- sion. Skillful use of side lighting for illumination will help highlight many ridge details that might otherwise remain obscured. Photographs should also be taken to show the position of the questioned impression in relation to the overall crime scene.

Although photography is an important fi rst step in preserving an impres- sion, it must be considered merely a backup procedure that is available to the examiner should the impression be damaged before it reaches the crime labo- ratory. Naturally, the examiner prefers to receive the original impression to compare to the suspect shoe, tire, garment, and so forth. In most cases, when the impression is on a readily recoverable item, such as glass, paper, or fl oor tile, the evidence is easily transported intact to the laboratory.

222

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

FIGURE 28 A small child was found dead at the edge of a rural road near a railroad crossing, the victim of a hit-and-run driver. A local resident was suspected, but he denied any knowledge of the incident. The inves- tigating offi cer noted what appeared to be a fabric imprint on the bumper of the suspect’s automobile. The weave pattern of the clothing of the deceased was compared with the imprint on the bumper and was found to match. When the suspect was confronted with this information, he admitted his guilt. Courtesy Centre for Forensic Sciences, Toronto, Canada

FIGURE 27 (a) An impression of a shoe found at a crime scene. (b) A test impression made with a suspect shoe. A suffi cient number of points of comparison exist to support the conclusion that the suspect shoe left the impression at the crime scene.

(a) (b)

223

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

LIFTING IMPRESSIONS

If an impression on a surface that cannot be submitted to the laboratory is encountered, the investigator may be able to preserve the print in a manner that is analogous to lifting a fi ngerprint. This is especially true of impressions made in light deposits of dust or dirt. A lifting material large enough to lift the entire impression should be used. Carefully place the lifting material over the  entire impression. Use a fi ngerprint roller to eliminate any air pockets before lifting the impression off the surface.

A more exotic approach to lifting and preserving dust impressions involves the use of a portable electrostatic lifting device. The principle is similar to that of creating an electrostatic charge on a comb and using the comb to lift small pieces of tissue paper. A sheet of Mylar fi lm is placed on top of the dust mark, and the fi lm is pressed against the impression with the aid of a roller. The high- voltage electrode of the electrostatic unit is then placed in contact with the fi lm while the unit’s earth electrodes are placed against a metal plate, or earth plate (see Figure 30 ). A charge difference develops between the Mylar fi lm and the surface below the dust mark, so the dust attaches to the lifting fi lm. In this man- ner, dust prints on chairs, walls, fl oors, and the like, can be transferred to Mylar fi lm. Floor surfaces up to 40 feet long can be covered with a Mylar sheet and searched for dust impressions. The electrostatic lifting technique is particularly helpful in recovering barely visible dust prints on colored surfaces. Dust im- pressions can also be enhanced through chemical development (see Figure 31 ).

CASTING IMPRESSIONS

Shoe and tire marks impressed into soft earth at a crime scene are best preserved by photography and casting. Class I dental stone, a form of gypsum, is widely recommended for making casts of shoe and tire impressions. The cast should be allowed to air-dry for 24 to 48 hours before it is shipped

FIGURE 29 A bloody imprint of a shoe was found on the carpet in the home of a homicide victim. (b) The suspect’s shoe, shown in (a), made the impression. Note the distinctive impression of the hole present in the shoe’s sole. Courtesy Dade County Crime Lab

WebExtra 7

Casting a Footwear Impression www.mycrimekit.com

(a) (b)

224

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

FIGURE 30 Electrostatic lifting of a dust impression off a fl oor using an electrostatic unit. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, NC, www.sirchie.com

FIGURE 31 (a) A dust impression of a shoe print on cardboard before enhancement. (b) A shoe print after chemical enhancement with bromophenol blue and exposure to water vapor. Courtesy Division of Identifi cation and Forensic Science, Israel Police Headquarters

(a)

(b)

225

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

to the forensic science laboratory for examination. Figure 32 illustrates a cast made from a shoe print in mud. The cast compares to the suspect shoe.

An aerosol product known as Snow Impression Wax is available for casting snow impressions. The recommended procedure is to spray three light coats of the wax at an interval of one to two minutes between layers, and then let it dry for ten minutes. A viscous mixture of Class I dental stone is then poured into the wax-coated impression. After the casting material has hardened, the cast can be removed.

Several chemicals can be used to develop and enhance footwear impres- sions made with blood. In areas where a bloody footwear impression is very faint or where a subject has tracked through blood, leaving a trail of bloody impressions, chemical enhancement can visualize latent or nearly invisible footwear impressions (see Figure 33 ).

Several blood enhancement chemicals have been examined for their impact on short tandem repeat (STR) DNA typing. None of the chemicals ex- amined had a deleterious effect, on a short-term basis, on the ability to carry out STR DNA typing on the blood. 5

COMPARING IMPRESSIONS

Whatever the circumstances, the laboratory procedures used to examine any type of impression remain the same. Of course, a comparison is possible only when the item suspected of having made the impression is recovered. Test impressions may be necessary to compare the characteristics of the suspect item with the evidence impression.

The evidential value of the impression is determined by the number of class and individual characteristics that the examiner fi nds. Agreement with respect to size, shape, or design may permit the conclusion that the impression

FIGURE 32 (a) A shoe impression in mud. (b) A cast of a shoe impression. (c) A shoe suspected of leaving the muddy impression. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

(a) (c)(b)

226

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

FIGURE 33 (a) A bloody footprint on cardboard treated with amido black. (b) A bloody footprint treated with Hungarian red dye. (c) A bloody footprint visualized with leucocrystal violet. (d) A bloody footprint enhanced with patent blue. (a) Courtesy Dwane S. Hilderbrand and David P. Coy, Scottsdale Police Crime Laboratory, Scottsdale, AZ; (b) Courtesy ODV Inc., South Plains, Maine; (c–d) Courtesy William Bodziak, FBI Laboratory

(a)

(c) (d)

(b)

227

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

CLOSER ANALYSIS CASTING FOOTWEAR AND TIRE IMPRESSIONS

Footwear and tire impressions may be found at any type of crime scene and can provide a primary means to identify or exclude a sus- pect. The preferred method of collection for this type of evidence is casting the impression—that is, making a mold and preserving it for analysis in the lab. When a footwear or tire impression is found in dirt at the crime scene, the casting process is as follows:

MATERIALS

Ruler

One small can of aerosol hair spray

1-gallon zip-top bag

Paint stirrer or large, long-handled spoon

Carton of dental stone

Water

Camera

Plastic or metal casting frame (optional)

Procedure 1. Retrieve any fragments or debris that is not imbedded within the

impression. Photograph the impression before and after retrieving debris; include a ruler in the photograph. A frame for containing the dental stone may be installed around an impression that is shallow or located on an inclined surface.

2. To solidify the soil, a fi xative such as hair spray is used (see [a]). Hold the can of hair spray about 18 inches from the soil within the impression. Very lightly, spray an even layer to the impression using a sweeping motion and taking care to avoid any damage to the impression.

3. Wait ten minutes to allow the hair spray to dry.

4. Add an appropriate amount of water to a premeasured amount of dental stone (see [b]). Add water in increments. The usual amount is about 10 to 12 fl uid ounces of water to about 1.5 to 2 pounds of dental stone. If using a zip-top bag, seal the bag and mix by work- ing back and forth with your fi ngers for at least three minutes (see [c]). Mix until a pancake-batter-like consistency is reached.

(continued )

Casting a footwear impression at a crime scene: (a) The impression is hardened using aerosol hair spray. (b) The correct amount of water is added to a known amount of dental stone. (c) The mixture is kneaded by hand until the desired (pancake-batter-like) consistency is reached. (d) The dental stone is poured into the impression using a spoon as a medium to disperse the fl ow. (e) The impression is fi lled with dental stone and allowed to dry before removal. Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

(a) (c)

(d) (e)

(b)

228

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

could have been made by a particular shoe, tire, or garment, but one cannot entirely exclude other possible sources from having the same class character- istics. More signifi cant is the existence of individual characteristics arising out of wear, cuts, gouges, or other damage. A suffi cient number or the uniqueness of such points of comparison supports a fi nding that both the evidence and test impressions originated from only one source.

When a tire tread impression is left at a crime scene, the laboratory can examine the design of the impression and possibly determine the style and/or manufacturer of the tire. This may be particularly helpful to investiga- tors when a suspect tire has not yet been located.

New computer software may help the forensic scientist compare shoe prints. For example, an automated shoe print identifi cation system devel- oped in England, called shoeprint image capture and retrieval (SICAR), in- corporates multiple databases to search known and unknown footwear fi les for comparison against footwear specimens. With the system, an impression from a crime scene can be compared to a reference database to fi nd out what type of shoe caused the imprint. That same impression can also be searched in the suspect and crime databases to reveal whether that shoe print matches the shoes of a person who has been in custody or the shoe prints left behind at

5. Open one corner of the bag. Pour the dental stone through the opening onto the ground beside the impression and allow it to carefully run into the impression. Use a paint stirrer, a spoon, or a gloved hand as a medium to disperse the stream so it does not destroy the fi ne details of the impression (see [d]). Continue pouring until the dental stone completely fi lls the impression (see [e]) and reaches at least 1/2 inch in thickness. If necessary, addi- tional casting material may be poured over the top of the original cast to add thickness.

6. Label the wet plaster surface with the date, initials, and any other information required for evidence labeling.

7. When the cast no longer adheres to the soil and is relatively dry (usually about one hour), remove the cast. If necessary, the cast can be dug out from the sides.

8. Store the cast for 48 hours to allow it to dry completely. If a cast is not allowed to dry long enough, some ridge details may disappear.

9. Once the cast is dry, rinse any loose soil from it with softly running water. A soft-bristled brush may also be used. Do not scrub or pick off anything. Pat dry with paper towels.

CLOSER ANALYSIS (continued)

FIGURE 34 (a) A bite mark impression on the victim’s forearm. (b) An upper dental model from the teeth of the suspect matches the individual tooth characteristics of the bite marks. Courtesy the late Haskin Askin, D.D.S., Chief Forensic Odontologist, Brick Town, NJ 08724

(a) (b)

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FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

CASEFILES THE O. J. SIMPSON TRIAL:

WHO LEFT THE IMPRESSIONS AT THE CRIME SCENE?

On the night of June 12, 1994, Nicole Brown—ex-wife of football star O. J. Simpson—and her friend Ron Goldman were brutally murdered on the grounds outside her home in Brentwood, California. O. J.  Simpson was arrested for their murders but professed his innocence. At the crime scene, investigators found bloody shoe impressions along the concrete walkway leading up to the front door of Brown’s condominium. These shoe impressions were of extremely high quality and of intricate detail. The news media broadcast count- less images of these bloody shoe prints on television, making it obvi- ous to the killer that those shoes would surely link him to the crime.

Famed FBI shoe print examiner William J. Bodziak investigated the footwear evidence from the scene. His fi rst task was to identify the brand of shoe that made the marks. Because the pattern was very clear and distinct, with complete toe-to-heel detail, this seemed like a simple task at fi rst. Bodziak compared this pattern to the thousands of sole patterns in the FBI’s database. None matched. He then went to his reference collection of books and trade show brochures, again with no success.

Bodziak’s experience told him that these were expensive, Italian- made casual dress shoes with a sole made from synthetic material. Using this knowledge, he shopped the high-end stores for a similar tread pattern but still was unable to identify the shoes. He then drew a composite sketch of the sole and faxed the image to law enforce- ment agencies and shoe manufacturers and distributors worldwide. The owner of the American distributing company for Bruno Magli shoes was the only one to respond.

Further exhaustive investigation revealed that these were extremely rare shoes. There were two styles of shoe bearing this exact sole design. They had been available for only two years at a mere forty stores in the United States and Puerto Rico. The Lorenzo style had a bootlike upper that came to the ankle. The Lyon style had a lower, more typical dress shoe shape. The impressions had been made by a size 12 shoe, and it was later determined that only 299 pairs of size 12 with this tread pattern were sold in the United States.

Simpson fl atly denied ever owning these shoes, adding that he would never wear anything so ugly. However, he was known to wear a size 12, and photographs taken almost nine months before the murders show Simpson wearing a pair of black leather Bruno Magli Lorenzo shoes. These shoes were available in several colors, so this narrows the number of shoes matching Simpson’s pair of Lorenzos (this size, color, and style) sold in the United States to twenty-nine pairs.

Proving that Simpson owned a pair of shoes that had the exact pattern found printed in blood at the crime scene was an essential component of the case, but it was not done in time to be used during the criminal prosecution. The photographs of Simpson in his Bruno Magli shoes were released after the culmination of the criminal trial, so the jury never heard the direct evidence that Simpson owned these shoes. However, this proved to be an important link uniting Simpson with the crime scene in the civil trial. Although O. J. Simpson was acquitted of the murders of Nicole Brown and Ron Goldman in the criminal trial, he was judged responsible for their murders in the civil court case.

Quick Review • Shoe and tire marks impressed into soft earth at a crime scene are best

preserved by photography and casting. • The electrostatic lifting technique is particularly helpful in recovering

barely visible dust prints on fl oor surfaces. • In areas where a bloody footwear impression is very faint or where the subject

has tracked through blood and left a trail of bloody impressions, chemical enhancement can visualize latent or nearly invisible blood impressions.

another crime scene. When matches are made during the searching process, the images are displayed side by side on the computer screen .

Human bite marks on skin and foodstuffs have been important items of evidence for convicting defendants in a number of homicide and rape cases in recent years. If a suffi cient number of points of similarity between test and suspect bite marks are present, a forensic odontologist may conclude that a bite mark was made by a particular individual (see Figure 34 ).

VIRTUAL LAB Footwear Impressions To perform a virtual footwear impression analysis, go to www.pearsoncustom.com/us/vlm/

VIRTUAL LAB Tool Mark Analysis To perform a virtual tool mark analysis, go to www.pearsoncustom.com/us/vlm/

230

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

CHAPTER REVIEW

• The manufacture of a gun barrel requires impressing its inner surface with spiral grooves, a step known as rifl ing. Rifl ing imparts spin to the projectile when it is fi red, which keeps it on an accurate course.

• No two rifl ed barrels have identical striation markings. These striations form the individual characteristics of the barrel. The inner surface of the barrel of a gun leaves its striation markings on a bullet passing through it.

• The class characteristics of a rifl ed barrel include the number of lands and grooves and the width and direction of twist.

• The comparison microscope is a fi rearms examiner’s most important tool because it allows two bullets to be compared simultaneously.

• The fi ring pin, breech face mark, and ejector and extractor mechanism also offer a highly distinctive signature for indi- vidualization of cartridge cases.

• Unlike handguns, a shotgun is not rifl ed—it has a smooth barrel. Because of this, shotgun shells are not impressed with any characteristic rifl ing striation markings that can be used to compare two shotgun shells to determine whether they were fi red from the same weapon.

• The advent of computerized imaging technology has made possible the storage of bullet and cartridge surface character- istics in a manner analogous to automated fi ngerprint fi les.

• Two automated fi rearms search systems are DRUGFIRE, developed by the FBI, and IBIS, developed by the ATF.

• NIBIN is the National Integrated Ballistics Information Net- work, a unifi ed fi rearms search system that incorporates both DRUGFIRE and IBIS technologies.

• The distribution of gunpowder particles and other discharge residues around a bullet hole permits an assessment of the distance from which a handgun or rifl e was fi red.

• The precise distance from which a handgun or rifl e was fi red is determined by carefully comparing the powder residue pat- tern on the victim’s clothing to test patterns made when the suspect weapon is fi red at varying distances from a target.

• The Greiss test is a chemical test used to examine patterns of gunpowder residues around bullet holes. It tests for the presence of nitrates.

• Firing a weapon propels residues toward the target and blows gunpowder and primer residues back toward the shooter. Traces of these residues are often deposited on the fi ring hand of the shooter, providing valuable information about whether an individual has recently fi red a weapon.

• Examiners measure the amount of barium and antimony on the relevant portion of the suspect’s hands or characterize the morphology of particles containing these elements to determine whether a person has fi red or handled a weapon or was near a discharged fi rearm.

• Criminalists can restore serial numbers removed or obliter- ated by grinding, rifl ing, or punching.

• Because the metal crystals in the stamped zone are placed under a permanent strain that extends a short distance beneath the original numbers, the serial number can be restored through chemical etching.

• A suspect fi rearm should never be picked up by inserting an object into its barrel because this practice may alter the striation markings on test-fi red bullets.

• Before unloading a suspect weapon, the weapon’s hammer and safety position should be recorded, as well as the loca- tion of all fi red and unfi red ammunition in the weapon.

• The protection of class and individual markings on bullets and cartridge cases is the primary concern of the fi eld inves- tigator when recovering bullets and cartridge casings.

• The presence of minute imperfections on a tool imparts indi- viduality to that tool. The shape and pattern of such imper- fections are further modifi ed by damage and wear during the life of the tool.

• The comparison microscope is used to compare crime-scene tool marks with test impressions made with the suspect tool.

• Shoe and tire marks impressed into soft earth at a crime scene are best preserved by photography and casting.

• The electrostatic lifting technique is particularly helpful in recovering barely visible dust prints on fl oor surfaces.

• In areas where a bloody footwear impression is very faint or where the subject has tracked through blood and left a trail of bloody impressions, chemical enhancement can visualize latent or nearly invisible blood impressions.

231

KEY TERMS

REVIEW QUESTIONS

bore

breech face mark

caliber

choke

distance determination

ejector

extractor

fi rearms identifi cation

gauge

Greiss test

grooves

lands

rifl ing

1. Firearms can be divided into two categories: ______________ and ______________ guns.

2. Handguns, or pistols, are fi rearms that are designed to be held and fi red with one hand, and the most common types of handguns are ______________ , ______________ , and ______________ .

3. The ______________ features several fi ring chambers, each holding one cartridge, located within a revolving cylinder that lines the chamber up with the barrel mechanically when the round is fi red.

4. A cartridge for a shotgun, called a shell, contains numerous ball-shaped projectiles, called ______________ .

5. A shotgun barrel is not rifl ed and can also be narrowed toward the muzzle in order to concentrate shot when fi red. The degree of narrowing of the barrel is called the ______________ of the shotgun.

6. The ______________ is the original part of the bore left after rifl ing grooves are formed.

7. The diameter of the gun barrel is known as its ______________ .

8. True or False: The number of lands and grooves is a class characteristic of a barrel. ______________

9. The ______________ characteristics of a rifl ed barrel are formed by striations impressed into the barrel’s surface.

10. The most important instrument for comparing bullets is the ______________ .

11. To make a match between a test bullet and a recovered bullet, the lands and grooves of the test and evidence bullet must have identical widths, and the longitudinal ______________ on each must coincide.

12. True or False: It is always possible to determine the make of a weapon by examining a bullet it fi red. ______________

13. A shotgun has a(n) ______________ barrel.

14. The diameter of a shotgun barrel is expressed by the term ______________ .

15. True or False: Shotgun pellets can be individualized to a single weapon. ______________

16. True or False: A cartridge case can be individualized to a single weapon. ______________

17. The automated fi rearms search system developed by the FBI and ATF as a unifi ed system incorporating both DRUGFIRE and IBIS technologies is known as ______________ .

18. True or False: The distribution of gunpowder particles and other discharge residues around a bullet hole permits an approximate determination of the distance from which the gun was fi red. ______________

19. True or False: Without the benefi t of a weapon, an exam- iner can make an exact determination of fi ring distance. ______________

20. A halo of vaporous lead deposited around a bullet hole normally indicates a discharge ______________ to ______________ inches from the target.

21. If a fi rearm has been fi red more than 3 feet from a target, usually no residue is deposited, but a dark ring, known as ______________ , is observed.

22. As a rule of thumb, the spread in the pattern made by a 12-gauge shotgun increases 1 inch for every ______________ of distance from the target.

23. A(n) ______________ photograph may help visualize gun- powder deposits around a target.

24. True or False: One test method for locating powder residues involves transferring particles embedded on the target surface to chemically treated photographic paper. ______________

25. Current methods for identifying a shooter rely on the detec- tion of ______________ residues on the hands.

26. Determining whether an individual has fi red a weapon is done by measuring the elements ______________ and ______________ present on the hands.

27. True or False: Firings with all types of ammunition can be detected from hand swabbings with nitric acid. ______________

28. Microscopic primer and gunpowder particles on the adhe- sives applied to a suspected shooter’s hand can be detected with a(n) ______________ .

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

232

29. True or False: Restoration of serial numbers is possible because in the stamped zone the metal is placed under a permanent strain that extends beneath the original numbers. ______________

30. True or False: It is proper to insert a pencil into the barrel when picking up a crime-scene gun. ______________

31. Recovered bullets are initialed on either the ______________ or ______________ of the bullet.

32. True or False: Because minute traces of evidence such as paint and fi bers may be adhering to a recovered bullet, the investigator must take care to remove these trace materials immediately. ______________

33. True or False: Cartridge cases are best marked at the base of the shell. ______________

34. The clothing of the victim of a shooting must be handled so to prevent disruption of ______________ around bullet holes.

35. A(n) ______________ is any impression caused by a tool coming into contact with another object.

36. Tool marks compare only when a suffi cient number of ______________ match between the evidence and test markings.

37. Objects bearing tool marks either should be submitted intact to the crime lab, or a(n) ______________ should be taken of the tool mark.

38. An imprint may be lifted using lifting sheets or a(n) ______________ .

39. Shoe and tire marks impressed into soft earth at a crime scene are best preserved by ______________ and ______________ .

40. A wear pattern, cut, gouge, or other damage pattern can impart ______________ characteristics to a shoe.

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

APPLICATION AND CRITICAL THINKING

1. Name and briefl y describe two popular approaches for col- lecting gunshot residue from a suspect’s hands. What is the most specifi c method of analysis for gunshot residue?

2. You are investigating a shooting involving a 12-gauge shot- gun with a moderately high choke. The spread of the pattern made by the pellets measures 12 inches. In your opinion, which of the following is probably closest to the distance from the target to the shooter? Explain your answer and explain why the other answers are likely to be incorrect.

a) 18 yards

b) 12 yards

c) 6 yards

d) 30 yards

3. Criminalist Ben Baldanza is collecting evidence from the scene of a shooting. After locating the revolver suspected of fi ring the shots, Ben picks the gun up by the grip, unloads it, and places the ammunition in an envelope. He then attaches an identifi cation tag to the grip. Searching the scene, Ben fi nds a bullet lodged in the wall. He uses pliers to grab the bullet and pull it from the wall, then inscribes the bullet with his initials and places it in an envelope. What mistakes, if any, did Ben make in collecting this evidence?

4. How would you go about collecting impressions in each of the following situations?

a) You discover a shoe print in dry sand.

b) You discover a tool mark on a windowsill.

c) You discover tire marks in soft earth.

d) You discover a shoe print on a loose piece of tile.

e) You discover a very faint shoe print in dust on a colored linoleum fl oor.

5. Gunshot residue patterns (A) through (D) (contact, 1 inch, 6 inches, and 18 inches) from a 40-caliber pistol are shown below. Match the fi ring distance to each pattern.

(A) (B)

(C) (D)

233

ENDNOTES

1. Originally, the number of lead balls with the same diameter as the barrel would make a pound. For example, a 20-gauge shotgun has an inside diameter equal to the diameter of a lead ball that weighs 1/20 pound.

2. J. W. Kilty, “Activity After Shooting and Its Effect on the Retention of Primer Residues,” Journal of Forensic Sciences 20 (1975): 219.

3. G. E. Reed et al., “Analysis of Gunshot Residue Test Results in 112 Suicides,” Journal of Forensic Sciences 35 (1990): 62.

4. R. S. White and A. D. Owens, “Automation of Gunshot Residue Detection and Analysis by Scanning Electron

Microscopy/Energy Dispersive X-Ray Analysis (SEM/EDX),” Journal of Forensic Sciences 32 (1987): 895; W. L. Tillman, “Automated Gunshot Residue Particle Search and Charac- terization,” Journal of Forensic Sciences 32 (1987): 62.

5. C. J. Frégeau et al., “Fingerprint Enhancement Revisited and the Effects of Blood Enhancement Chemicals on Subsequent Profi ler Plus™ Fluorescent Short Tandem Repeat DNA Analysis of Fresh and Aged Bloody Fingerprints,” Journal of Forensic Sciences 45 (2000): 354.

FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

234

THE SAM SHEPPARD CASE: A TRAIL OF BLOOD Convicted in 1954 of bludgeoning his wife to death, Dr. Sam Sheppard achieved celebrity status when the storyline of TV’s The Fugitive was apparently mod- eled on his efforts to seek vindication for the crime he professed not to have committed. Dr. Sheppard, a physi- cian, claimed he was dozing on his living room couch when his pregnant wife, Marilyn, was attacked. Shep- pard’s story was that he quickly ran upstairs to stop the carnage but was knocked briefl y unconscious by the in- truder. The suspicion that fell on Dr. Sheppard was fueled by the revelation that he was having an adulterous affair. At trial, the local coroner testifi ed that a pool of blood on Marilyn’s pillow contained the impression of a “surgi- cal instrument.” After Sheppard had been imprisoned for ten years, the US Supreme Court set aside his conviction because of the “massive, pervasive, and prejudicial pub- licity” that had attended his trial.

In 1966 the second Sheppard trial commenced. This time, the same coroner was forced to back off from his in- sistence that the bloody outline of a surgical instrument was present on Marilyn’s pillow. However, a medical tech- nician from the coroner’s offi ce now testifi ed that blood on Dr. Sheppard’s watch was from blood spatter, indicat- ing that Dr. Sheppard was wearing the watch in the pres- ence of the battering of his wife. The defense countered with the expert testimony of eminent criminalist Dr. Paul Kirk. Dr. Kirk concluded that blood spatter marks in the bedroom showed the killer to be left-handed. Dr. Shep- pard was right-handed.

Dr. Kirk further testifi ed that Sheppard stained his watch while attempting to obtain a pulse reading. After less than twelve hours of deliberation, the jury failed to convict Sheppard. But the ordeal had taken its toll. Four years later Sheppard died, a victim of drug and alcohol abuse.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Discuss the information that can be gained from bloodstain

pattern analysis about the events involved in a violent crime. • Explain how surface texture, directionality, and angle

of impact affect the shape of individual bloodstains. • Calculate the angle of impact of a bloodstain using its

dimensions. • Describe the classifi cations of low-, medium-, and high-

velocity impact spatter and appreciate how these classifi cations should be used.

• Discuss the methods of determining the area of convergence and area of origin for impact spatter patterns.

• Understand how various blood pattern types are created and which features of each pattern can be used to aid in reconstructing events at a crime scene.

• Describe the methods for documenting bloodstain patterns at a crime scene.

Bloodstain

Pattern Analysis

© Bettmann / CORBIS All Rights Reserved

From Chapter 10 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

BLOODSTAIN PATTERN ANALYSIS

General Features of Bloodstain Formation Crimes involving violent contact between individuals are frequently accom- panied by bleeding and resultant bloodstain patterns. Crime-scene analysts have come to appreciate that bloodstain patterns deposited on fl oors, walls, ceilings, bedding, and other relevant objects can provide valuable insights into events that occurred during the commission of a violent crime. The infor- mation one is likely to uncover as a result of bloodstain pattern interpretation includes the following:

• The direction from which blood originated • The angle at which a blood droplet struck a surface • The location or position of a victim at the time a bloody wound was infl icted • The movement of a bleeding individual at the crime scene • The minimum number of blows that struck a bleeding victim • The approximate location of an individual delivering blows that produced

a bloodstain pattern

The crime-scene investigator must not overlook the fact that the location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that accompanied the bleeding. A thorough analysis of the signifi cance of the position and shape of blood patterns with respect to their origin and trajectory is exceedingly complex and requires the services of an examiner who is experienced in such determina- tions. Most important, the interpretation of bloodstain patterns necessitates a carefully planned control experiment using surface materials comparable to those found at the crime scene. This chapter presents the basic principles and common deductions behind bloodstain pattern analysis to give the reader general knowledge to use at the crime scene.

SURFACE TEXTURE

Surface texture is of paramount importance in the interpretation of bloodstain patterns; comparisons between standards and unknowns are valid only when identical surfaces are used. In general, harder and nonporous surfaces (such as glass or smooth tile) result in less spatter. Rough surfaces, such as a con- crete fl oor or wood, usually result in irregularly shaped stains with serrated edges, possibly with satellite spatter (see Figure 1 ).

FIGURE 1 (a) A bloodstain from a single drop of blood that struck a glass surface after falling 24 inches. (b) A bloodstain from a single drop of blood that struck a cotton muslin sheet after falling 24 inches. Courtesy, A.Y. Wonde

satellite spatter Blood spatter around parent stain, with blood droplets whose pointed ends face against the direction of travel.

(a)

(b)

236

BLOODSTAIN PATTERN ANALYSIS

DIRECTION AND ANGLE OF IMPACT

An investigator may discern the direction of travel of blood that struck an object by studying the stain’s shape. As the stain becomes more elliptical in shape, its direction becomes more discernable because the pointed end of a bloodstain faces its direction of travel. The distorted or disrupted edge of an elongated stain indicates the direction of travel of the blood drop. Satellite spatter around parent stains will have the pointed end facing against the direction of travel. In Figure 2 , the bloodstain pattern was produced by several droplets of blood that were traveling from left to right before striking a fl at, level surface.

It is possible to determine the impact angle of blood on a fl at surface by measuring the degree of circular distortion of the stain. A drop deposited at an angle of impact of about 90 degrees (directly vertical to the surface) will be ap- proximately circular in shape with no tail or buildup of blood. However, as the angle of impact deviates from 90 degrees, the stain becomes elongated in shape. Buildup of blood will occur when the angles are larger, whereas longer and longer tails will appear as the angle of impact becomes smaller (see Figure 3 ).

Quick Review • Individual bloodstains can convey to the bloodstain analyst the directional-

ity and angle of impact of the blood when it impacted a surface. Bloodstain patterns may convey to the analyst the location of the victim (who was bleeding) or suspect (who was causing the bleeding), the movement of bleeding individuals, and the number of blows delivered.

• Surface texture is of paramount importance in the interpretation of bloodstain patterns; rounder drops generally are produced on smooth, nonporous surfaces, whereas rough surfaces result in irregular-edged drops. However, correlations between standards and unknowns are valid only when identical surfaces are used.

• The direction of travel of blood that struck an object may be discerned by the stain’s shape. The pointed end of a bloodstain always faces its direction of travel.

FIGURE 2 A bloodstain pattern produced by droplets of blood that were traveling from left to right. Courtesy, A.Y. Wonde

FIGURE 3 The higher pattern is of a single drop of human blood that fell 24 inches and struck hard, smooth cardboard at 50 degrees. On this drop the collec- tion of blood shows the direction. The lower pattern is of a single drop of human blood that fell 24 inches and struck hard, smooth cardboard at 15 degrees. On this drop the tail shows the direction. Courtesy, A.Y. Wonde

angle of impact The angle of the source of the blood to the surface where it was deposited. It can be estimated from the width-to-length ratio of the stain to help determine the position of the victim or the weapon at the time when the bleeding wound was infl icted.

WebExtra 1

See How Bloodstain Spatter Patterns Are Formed www.mycrimekit.com

237

BLOODSTAIN PATTERN ANALYSIS

• The angle of impact of an individual bloodstain can be approximated by the degree of distortion or lengthening of the bloodstain, or it can be more effectively estimated using the width-to-length ratio of the stain.

Impact Bloodstain Spatter Patterns The most common type of bloodstain pattern found at a crime scene is impact spatter . This pattern occurs when an object impacts the source of the blood. Spatter projected outward and away from the source, such as an exit wound, is called forward spatter . Back spatter , sometimes called blow-back spatter , is blood projected backward from a source, such as an entrance wound, and potentially deposited on the object or person who created the impact. Impact spatter patterns consist of many droplets radiating in direct lines from the origin of blood to the stained surface (see Figure 4 ).

Investigators have derived a com- mon classifi cation system of impact spat- ter based on the velocity of the force impacting on a bloody object. In gen- eral, as the velocity of the force of the impact on the source of blood increases, so does the velocity of the blood drop- lets emanating from the source. It is also generally true that, as both the force and velocity of impact increase, the diameter of the resulting blood droplets decreases.

CLASSIFYING

IMPACT SPATTER

LOW-VELOCITY SPATTER An impact pattern consisting of a preponderance of large separate or compounded drops with diameters of 4 millimeters or more is known as low-velocity spatter . This kind of spatter is normally produced by gravity alone, by a minimal force, or by

FIGURE 4 Impact spatter produced by an automatic weapon. The arrows shows the multiple directions of travel from the origin of impact as several different bullets struck the target. Courtesy, A.Y. Wonde

impact spatter A bloodstain pattern produced when an object makes forceful contact with a source of blood, projecting droplets of blood outward from the source.

forward spatter Blood that travels away from the source in the same direction as the force that caused the spatter.

back spatter Blood directed back toward the source of the force that caused the spatter.

CLOSER ANALYSIS DETERMINING THE ANGLE OF IMPACT OF BLOODSTAINS

The distorted or disrupted edge of an elongated stain indicates the direction of travel of the blood drop. One may establish the location or origin of bloodshed by determining the directionality of the stain and the angle at which blood came into contact with the surface of impact. To determine the angle of impact, calculate the stain’s length- to-width ratio and apply the formula

Sin A 5 width of blood stain length of blood stain

Example: The width of a stain is 11 mm and the length is 22 mm.

Then, sin A 5 11 mm 22 mm

5 111 mm 4 22 mm2 5 0.50

A scientific calculator that has the trigonometry function will calculate that the inverse sine of 0.50 is equal to a 30-degree angle.

Note: The measurements for length and width should be made with a ruler, micrometer, or photographic loupe.

238

BLOODSTAIN PATTERN ANALYSIS

an object dropping into and splashing blood from a blood pool. Low-velocity stains can result from an applied force moving at up to 5 feet per second.

MEDIUM-VELOCITY SPATTER A pattern predominantly consisting of small drops with diameters of 1 to 4 millimeters is classifi ed as medium-velocity spatter . This type of impact spatter is normally associated with blunt force trauma to an individual or with other applied forces moving at between 5 to 25 feet per second.

HIGH-VELOCITY SPATTER Very fi ne droplets with a preponderance of diam- eters of less than 1 millimeter are classifi ed as high-velocity spatter . Here the spatter can result from an applied force of 100 feet per second or faster. Gunshot exit wounds or explosions commonly produce this type of spatter. However, because the droplets are very small, they may not travel far; they may fall to the fl oor or ground, where investigative personnel could overlook them.

Using droplet size to classify impact patterns by velocity is a useful tool that gives investigators insight into the general nature of a crime. However, the clas- sifi cations of low, medium, and high velocity cannot illuminate the specifi c events that produced the stain pattern. For example, beatings can produce either high-velocity spatter or stain sizes that look more like low- velocity spatter. In general, one should use stain size categories very cautiously, and for descriptive purposes only, in evaluating impact spatter patterns. A more acceptable approach for classifying a bloodstain pattern should encompass observations of stain size, shape, location, and distribution.

Blood spatter patterns can arise from a number of distinctly different sources, which will be discussed in this chapter. Illustrations of patterns emanating from im- pact, cast-off, and arterial spray are shown in Figure 5 .

ORIGIN OF IMPACT PATTERNS

Impact spatter patterns can offer investigators clues about the origin of the blood spatter and, therefore, the position of the victim at the time of the impact.

FIGURE 5 (a) The action associated with producing impact spatter. (b) The action associated with producing cast-off spatter. (c) The action associated with producing arterial spray spatter. Courtesy, A.Y. Wonde

low-velocity spatter An impact spatter pattern created by a force traveling at 5 feet per second or less and producing drops with diameters of greater than 4 millimeters.

medium-velocity spatter An impact spatter pattern created by a force traveling at 5 to 25 feet per second and producing drops with diameters of between 1 and 4 millimeters.

(a)

(b) (c)

239

BLOODSTAIN PATTERN ANALYSIS

AREA OF CONVERGENCE The area of convergence is the point on a two- dimensional plane from which the drops originated. This can be estab- lished by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails. The intersection of these lines is the area of convergence, and the approximate point of origin will be on a line straight out from this area. Figure 6 illustrates how to draw lines to fi nd an area of convergence.

An object hitting a source of blood numerous times will never produce exactly the same pattern each time. One can therefore determine the number of impacts by drawing the area of convergence for groups of stains from sepa- rate impacts.

AREA OF ORIGIN It may also be important to determine the area of origin of a bloodstain pattern, the area in a three-dimensional space from which the blood was projected. This will show the position of the victim or suspect in space when the stain-producing event took place. The distribution of the drop- lets in an impact pattern gives a general idea of the distance from the blood source to the bloodstained surface. Impact patterns produced at a distance close to the surface will appear as clustered stains. As the distance from the surface increases, so do the distribution and distance between droplets.

A common method for determining the area of origin at the crime scene is called the string method . Figure 7 illustrates the steps in the string method:

1. Find the area of convergence for the stain pattern. 2. Place a pole or stand as an axis coming from the area of convergence. 3. Attach one end of a string next to each droplet. Place a protractor next to

each droplet and lift the string until it lines up with the determined angle

Convergence

FIGURE 6 An illustration of stain convergence on a two-dimensional plane. Convergence represents the area from which the stains emanated. Courtesy Judith Bunker, J.L. Bunker & Assoc., Ocoee, FL

area of origin The location in three-dimensional space that blood that produced a bloodstain originated from. The location of the area of convergence and the angle of impact for each bloodstain is used to approximate this area.

high-velocity spatter An impact spatter pattern created by a force traveling at 100 feet per second or faster and producing droplets with diameters of less than 1 millimeter.

area of convergence The area on a two-dimensional plane where lines traced through the long axis of several individual bloodstains meet. This approximates the two-dimensional place from which the bloodstains were projected.

240

BLOODSTAIN PATTERN ANALYSIS

of impact of the drop. Keeping the string in line with the angle, attach the other end of the string to the axis pole.

4. View the area of origin of the droplets where the strings appear to meet. Secure the strings at this area.

Quick Review • An impact spatter pattern occurs when an object impacts a source of

blood. This produces forward spatter projected forward from the source and back spatter projected backward from the source.

• Impact spatter patterns can be classifi ed as low-velocity (�4 mm drops), medium-velocity (1–4 mm drops), or high-velocity (�1 mm drops) for

FIGURE 7 An illustration of the string method used at a crime scene to determine the area of origin of blood spatter. Bloodstain Pattern Evidence, by A. Y. Wonder, p. 295. Copyright Elsevier, 2007.

241

BLOODSTAIN PATTERN ANALYSIS

descriptive purposes. These categories should not be used to make assumptions about what kind of force created the pattern.

• The area of convergence is the point on a two-dimensional plane from which the drops of an impact spatter pattern originated. This area can be estimated by drawing straight lines through the long axis of several indi- vidual bloodstains, following the line of their tails.

• The area of origin of a bloodstain pattern is the area in three-dimensional space where blood was projected from, showing the position of the victim or suspect when the stain-producing event took place. The string method is commonly used at a crime scene to approximate the area of origin.

More Bloodstain Spatter Patterns GUNSHOT SPATTER

A shooting may leave a distinct gunshot spatter pattern. This may be characterized by both forward spatter from an exit wound and back spatter from an entrance wound. The presence of backspatter on a fi rearm or a shooter is dependent on the distance between the fi rearm and victim. Forward spatter generally leaves a pattern of very fi ne droplets characteristic of high-velocity spatter (see Figure 8 ). Medium- and large-sized drops may also be observed within the spatter pattern.

The location of injury, the size of the wound created, and the distance between the victim and the muzzle of the weapon all affect the amount of back spatter that occurs. Finding high-velocity spatter containing the victim’s blood on a suspect can help investigators place the suspect in the vicinity when the gun was discharged. Back spatter created by a gunshot impact generally contains fewer and smaller, atomized stains than does forward spatter. Muzzle blast striking an entrance wound will cause the formation of atomized blood.

Depending on the distance from the victim that the gun was discharged, some back spatter may strike the gunman and enter the gun muzzle. This is called

the drawback effect . Blood within the muzzle of a gun can “place” the weapon in the vicinity of the gun- shot wound. The presence of blow- back spatter on a weapon’s muzzle is consistent with the weapon’s hav- ing been close to the victim at the time of fi ring (see Figure 9 ).

FIGURE 8 The high-velocity spatter from the cone-shaped deposit of gunshot spatter. Cour- tesy, A.Y. Wonde

FIGURE 9 Back spatter bloodstains en- tering the muzzle of a weapon discharged in close proximity to a victim. Courtesy Ralph R. Ristenbatt lll and Robert Shaler.

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BLOODSTAIN PATTERN ANALYSIS

CAST-OFF SPATTER

A cast-off pattern is created when a blood-covered object fl ings blood in an arc onto a nearby surface. This kind of pattern commonly occurs when a person pulls a bloody fi st or weapon back between delivering blows to a victim (see Figure 5 [b]). The bloodstain tails will point in the direction that the object was moving.

The width of the cast-off pattern created by a bloody object may help suggest the kind of object produced by the pattern. The sizes of the drops are directly related to the size of the point from which they were propelled. Drops propelled from a small or pointed surface will be smaller and the pattern more linear; drops propelled from a large or blunt surface will be larger and the pattern wide. The volume of blood deposited on an object from the source also affects the size and number of droplets in the cast-off pattern. The less blood on the object, the smaller the stains produced. The pattern may also suggest whether the blow that caused the pattern was directed from right to left or left to right. The pattern will point in the direction of the backward thrust, which will be opposite the direction of the blow. This could suggest which hand the assailant used to deliver the blows.

Cast-off patterns may also show the minimum number of blows delivered to a victim. Each blow should be marked by an upward- and-downward or forward-and- backward arc pattern (see Figure 10 ). By counting and pairing the patterns, one can

CASE FILES BLOOD SPATTER EVIDENCE

Stephen Scher banged on the door of a cabin in the woods outside Montrose, Pennsylvania. According to Scher, his friend, Marty Dillon, had just shot himself while chasing after a porcupine. The two had been skeet shooting at Scher’s cabin, enjoying a friendly sporting weekend, when Dillon spotted a porcupine and took off out of sight. Scher heard a single shot and waited to hear his friend’s voice. After a few moments, he chased after Dillon and found him lying on the ground near a tree stump, bleeding from a wound in his chest. Scher administered CPR after locating his dying friend, but he was unable to save Dillon, who later died from his injuries. Police found that Dillon’s untied boot had been the cause of his shotgun wound. They determined he had tripped while running with his loaded gun and shot himself. The grief-stricken Scher aroused no suspicion, so the shooting was ruled an accident.

Shortly thereafter, Scher moved away from Montrose, divorced his wife, and married Dillon’s widow. This was too suspicious to be ignored; police reopened the case and decided to reconstruct the

crime scene. The reconstruction provided investigators with several pieces of blood evidence that pointed to Scher as Dillon’s murderer.

Police noticed that Scher’s boots bore the unmistakable spray of high-velocity impact blood spatter, evidence that he was standing within an arm’s length of Dillon when Dillon was shot. This pattern of bloodstains would not be expected to be created while administering CPR, as Scher claimed had happened. The spatter pattern also clearly refuted Scher’s claim that he did not witness the incident. In addition, the tree stump near Dillon’s body bore the same type of blood spatter, in a pattern that indicated Dillon was seated on the stump , not run- ning, when he was shot. Finally, Dillon’s ears were free of the high-ve- locity blood spatter that covered his face, but blood was on his hearing protectors found nearby. This is a clear indication that he was wearing his hearing protectors when he was shot and they were removed be- fore investigators arrived. This and other evidence resulted in Scher’s conviction for the murder of his long-time friend, Marty Dillon.

FIGURE 10 The cast-off pattern created from one backward and one forward motion of an overhand swing. Larger drops are deposited in the motion away from the victim because they’re made when the weapon holds the greatest amount of blood. The smaller spatters are directed toward the victim. Bloodstain Pattern Evidence by A. Y. Wonder, p. 295. Copyright Elsevier, 2007.

cast-off A bloodstain pattern that is created when blood is fl ung from a blood-bearing object in motion onto a surface.

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BLOODSTAIN PATTERN ANALYSIS

estimate the minimum number of blows. An investigator should take into consideration that the fi rst blow would only cause blood to pool to the area; it would not produce a cast-off pattern. Also, some blows may not come into contact with blood and therefore will not produce a pattern. The medical examiner is in the best position to estimate the number of blows a victim received.

ARTERIAL SPRAY SPATTER

Arterial spray spatter is created when a victim suffers an injury to a main artery or the heart. The pressure of the continuing pump- ing of blood causes blood to spurt out of the injured area (see Figure 5 [c]). Commonly, the pattern shows large spurted stains for each time the heart pumps. Some radial spikes, satellite spatter, or fl ow patterns may be evident because of the large volume of blood being expelled with each spurt. Drops may also be seen on the sur- face in fairly uniform size and shape and in parallel arrangement (see Figure 11 ).

The lineup of the stains shows the victim’s movement. Any verti- cal arcs or waves in the line show fl uctuations in blood pressure. The larger arterial stains are at the end of the overall pattern. The site of the initial injury to the artery can be found where the pattern begins with the biggest spurt. Arterial patterns can also be differentiated because the oxygenated blood spurting from the artery tends to be a brighter red color than blood expelled from impact wounds.

EXPIRATED BLOOD

PATTERNS

A pattern created by blood that is expelled from the mouth or nose from an internal injury is called an expirated blood pat- tern . If the blood that creates such a pat- tern is under great pressure, it produces very fi ne high-velocity spatter. Expirated blood at very low velocities produces a stain cluster with irregular edges (see Figure 12 ). The presence of bubbles of oxygen in the drying drops can differ- entiate a pattern created by expirated blood from other types of bloodstains. Expirated blood also may be lighter in color than impact spatter as a result of being diluted by saliva. The presence of expirated blood gives an important clue to the injuries suffered and the events that took place at a crime scene.

VOID PATTERNS

A void is created when an object blocks the deposition of blood spatter onto a surface or object (see Figure 13 ). The

FIGURE 11 Arterial spray spatter found at a crime scene where a victim suffered injury to an artery. Courtesy Norman H. Reeves, Blood- stain Pattern Analysis, Tucson, AZ, www.bloody1.com

FIGURE 12 An example of expirated blood expelled with two wheezes from the mouth Courtesy, A.Y. Wonde

arterial spray A characteristic bloodstain pattern caused by spurts that resulted from blood exiting under pressure from an arterial injury.

244

BLOODSTAIN PATTERN ANALYSIS

spatter is deposited onto the object or person instead. The blank space on the surface or object may give a clue to the size and shape of the missing object or person. Once the object or person is found, the missing piece of the pattern should fi t in, much like a puzzle piece, with the rest of the pattern. Voids may help establish the body position of the victim or assailant at the time of the incident.

Quick Review • Gunshot spatter can consist of both forward spatter from an exit wound

and back spatter from an entrance wound; however, only back spatter will be produced if the bullet does not exit the body.

• A cast-off pattern is created when a blood-covered object fl ings blood in an arc onto a nearby surface. This kind of pattern commonly occurs when a person pulls a bloody fi st or weapon back between delivering blows to a victim.

• The characteristic arterial spray spatter is created when a victim suffers an injury to a main artery or the heart, and the pressure of the continuing pumping of blood projects blood out of the injured area in spurts, which are apparent in the pattern.

• Expirated blood is expelled from the mouth or nose and may appear as very fi ne high-velocity spatter or large low-velocity bloodstain clusters. This kind of pattern may contain bubbles of oxygen or be mixed with saliva.

• A void pattern is an area free of spatter where an object (or person) blocked the deposition of blood spatter onto a surface or object. Because the spatter was deposited onto the object or person instead, the shape of the void may give a clue about the size and shape of the missing object or person.

expirated blood pattern A pattern created by blood that is expelled out of the nose, mouth, or respiratory system as a result of air pressure and/or airfl ow.

void An area within a deposited spatter pattern that is clear of spatter, caused by an object or person’s blocking the area at the time of the spatter’s deposition.

FIGURE 13 A void pattern is found behind a door where the surface of the door blocked the deposition of spatter on that area. This void, and the presence of spatter on the door, shows that the door was open when the spatter was deposited. Courtesy Norman H. Reeves, Blood- stain Pattern Analysis, Tucson, AZ, www.bloody1.com

245

BLOODSTAIN PATTERN ANALYSIS

Other Bloodstain Patterns Not all bloodstains at a crime scene appear as spatter patterns. The circumstances of the crime often create other types of stains that can be useful to investigators.

CONTACT/TRANSFER PATTERNS

When an object with blood on it touches another object that did not have blood on it, this produces a contact or transfer pattern . Examples of transfers

with features include fi ngerprints (see Figure 14 ), handprints, footprints, footwear prints, tool prints, and fabric prints in blood. These may provide further leads by offering individual characteristics.

The size and general shape of a tool may be seen in a simple transfer. This can lead to narrowing the possible tools by class characteristics. A transfer that shows a very individualistic feature may help point to the tool that made the pattern.

Simple transfer patterns are produced when the bloody object makes contact with a surface and the object is removed without any further movement. Other transfers known as swipe patterns may be caused by movement of the bloody object across a sur- face. Generally, the pattern will lighten and “feather” as the pattern moves away from the initial contact point (see Figure 15 ). However, because “feathering” is also a function of the amount of pressure being

FIGURE 14 A transfer pattern consisting of bloody fi ngerprints with ap- parent ridge detail. Courtesy Lawrence A. Presley, Arcadia University

FIGURE 15 A series of swipe patterns moving from right to left. Courtesy, A.Y. Wonder

transfer pattern A bloodstain pattern created when a surface that carries wet blood comes into contact with a second surface. Recognizable imprints of all or a portion of the original surface or the direction of movement may be observed.

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BLOODSTAIN PATTERN ANALYSIS

applied to the surface, the analyst must interpret directionality with care. The direction of separate bloody transfers, such as footwear prints in blood, may show the movement of the suspect, victim, or others through the crime scene after the blood was present. The fi rst transfer pattern will be dark and heavy with blood, whereas subsequent transfers will be increasingly lighter in color. The transfers get lighter as less and less blood is deposited from the trans- ferring object’s surface. Bloody shoe imprints may also suggest whether the wearer was running or walking. Running typically produces imprints with more space between them and more satellite or drop patterns between each imprint.

FLOWS

Patterns made by drops or large amounts of blood fl owing with the pull of gravity are called fl ows . Flows may be formed by single drops or large volumes of blood coming from an actively bleeding wound or blood deposited on a surface, from an arterial spurt, for example. Clotting of the blood’s solid parts may occur when a fl ow extends onto an absorbent surface.

The fl ow direction may show movements of objects or bodies while the fl ow was still in progress or after the blood had dried. Figure 16 illustrates a situation in which movement of the surface while the fl ow was still in progress led to a specifi c pattern.

Interruption of a fl ow pattern may be helpful in assessing the sequence and passage of time be- tween the fl ow and its interrup- tion. If a fl ow found on an object or body does not appear to be consistent with the direction of gravity, one may surmise that the object or body was moved after the blood had dried.

POOLS

A pool of blood occurs when blood collects in a level (not sloped) and undisturbed place. Blood that pools on an absorbent surface may be absorbed throughout the surface and diffuse, creating a pat- tern larger than the original pool. This often occurs to pools on beds or sofas.

The approximate drying time of a pool of blood is related to the environmental condition of the scene. By experimentation, an analyst may be able to reasonably estimate the drying times of stains of different sizes. Small and large pools of blood can be helpful in reconstruction be- cause they can be analyzed to estimate the amount of time that has elapsed since the blood was deposited. Considering the drying time of a blood pool can yield information about the timing of events that accompanied the incident.

The edges of a stain will dry to the surface, producing a phenomenon called skeletonization (see Figure 17 ). This usually occurs within 50 seconds of deposition for droplets, and it takes longer for larger volumes of blood. If

FIGURE 16 The fl ow pattern suggests that the victim was upright and then fell while blood fl owed. The assailant claimed the victim was stabbed while sleeping. Courtesy, A.Y. Wonde

fl ow A bloodstain pattern formed by the movement of small or large amounts of blood as a result of gravity’s pull.

skeletonization The process by which the edges of a bloodstain dry to the surface in a specifi c period of time (dependent on environmental and surface conditions). Skeletonization will remain apparent even after the rest of the bloodstain has been disturbed from its original position.

247

BLOODSTAIN PATTERN ANALYSIS

the central area of the pooled bloodstain is then altered by wiping, the skel- etonized perimeter will be left intact. This can be used to interpret whether movement or activity occurred shortly after the pool was deposited or later, after the perimeter had time to skeletonize fi rst. This may be important for classifying the source of the original stain.

DROP TRAIL PATTERNS

A drop trail pattern is a series of drops that is separate from other patterns, and it is formed by blood dripping off an object or injury. The stains form a kind of line, usually the path made by the suspect after injuring or killing the victim. It may simply show movement, lead to a discarded weapon, or provide identifi cation of the suspect if it is made from his or her own blood. Investi- gators often see this type of pattern in stabbings during which the criminal inadventently cuts him- or herself as a result of using the force necessary to stab the victim. Figure 18 shows a drop trail pattern away from the center of action at a crime scene.

The shape of the stains in a drop trail pattern can help investigators deter- mine the direction and speed at which a person was moving. The tails of the drops in a trail pattern point in the direction the person was moving. More circular stains are found where the person was moving slowly. This informa- tion may be helpful in reconstruction.

FIGURE 17 Skeletonization is shown in a bloodstain that was disturbed after the edges had time to dry. Courtesy, A.Y. Wonde

FIGURE 18 A drop trail pattern leads away from the center of the mixed bloodstain pattern. Courtesy Norman H. Reeves, Blood- stain Pattern Analysis, Tucson, AZ, www.bloody1.com

drop trail pattern A pattern of bloodstains formed by the dripping of blood off a moving surface or person in a recognizable pathway separate from other patterns.

248

BLOODSTAIN PATTERN ANALYSIS

CASE FILES BLOODSTAIN RECONSTRUCTION

An elderly male was found lying dead on his living room fl oor. He had been beaten about the face and head, stabbed in the chest, and robbed. The bloodstains found on the interior front door and the adjacent wall documented that the victim was beaten about the face with a fi st and struck on the back of the head with his cane. A three-dimensional dia- gram and photograph illustrating the evidential bloodstain patterns are shown in Figure 1(a) and (b) .

A detail photograph of bloodstains next to the interior door is shown in Figure 2 . Arrow 1 in Figure 2 points to the cast-off pattern directed left to right as blood was fl ung from the perpetrator’s fi st while infl icting blows. Arrow 2 in Figure 2 points to three transfer impression patterns directed left to right as the perpetrator’s blood- stained hand contacted the wall, as the fi st blows were being infl icted

on the victim. Arrow 3 in Figure 2 points to blood fl ow from the victim’s wounds as he slumped against the wall.

Figure 3 contains a series of laboratory test patterns created to evaluate the patterns contained within Figure 2 .

Figure 4 shows how the origin of individual impact spatter patterns located on the wall and door and emanating from the bleeding victim can be documented by the determination of separate areas of convergence.

A suspect was apprehended three days later, and he was found to have an acute fracture of the right hand. When he was confronted with the bloodstain evidence, the suspect admitted to striking the victim, fi rst with his fi st, then with a cane, and fi nally stabbing him with a kitchen knife. The suspect pleaded guilty to three fi rst-degree felonies.

FIGURE 1 (a) A three-dimensional diagram illustrating bloodstain patterns that were located, documented, and reconstructed; (b) a crime-scene photograph of blood-stained areas. The Institute of Applied Forensic Technology, Ocoee, Florida

FIGURE 2 Positions of impact spatter from blows that were infl icted on the victim’s face. The Institute of Applied Forensic Technology, Ocoee, Florida

(a) (b)

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BLOODSTAIN PATTERN ANALYSIS

FIGURE 3 (a) A laboratory test pattern showing an impact spatter. The size and shape of the stains demonstrate a forceful impact 90 degrees to the target. (b) A laboratory test pattern illustrating a cast-off pattern directed left to right from an over- head swing. (c) A laboratory test pattern showing a repetitive transfer impression pattern produced by a bloodstained hand moving left to right across the target. (d) A laboratory test pattern illustrating vertical fl ow patterns. The left pattern repre- sents a stationary source; the right pattern was produced by left-to-right motion. The Institute of Applied Forensic Technology, Ocoee, Florida

(a)

(d)

FIGURE 4 (a) A convergence of impact spatter patterns associated with beating with a fi st. (b) The convergence of impact spatter associated with the victim falling to the fl oor while bleeding from the nose. (c) The convergence of impact spatter associated with the victim being struck with a cane while lying face down at the door. The Institute of Applied Forensic Technology, Ocoee, Florida

(a)

(b)

(c)

(b) (c)

250

BLOODSTAIN PATTERN ANALYSIS

Documenting Bloodstain Pattern Evidence Blood spatter patterns of any kind can provide a great deal of information about the events that took place at a crime scene. For this reason, investiga- tors should note, study, and photograph each pattern and drop. This must be done to accurately record the location of specifi c patterns and to distinguish the stains from which laboratory samples were taken. The photographs and sketches can also point out specifi c stains used in determining the direction of force, angle of impact, and area of origin.

Just as in general crime-scene photography, the investigator should create photographs and sketches of the overall pattern to show the orienta- tion of the pattern to the scene. The medium-range documentation should include pictures and sketches of the whole pattern and the relationships between individual stains within the pattern. The close- up photographs and sketches should show the dimen- sions of each individual stain. Close-up photographs should be taken with a scale of some kind showing in the photograph.

Two common methods of documenting bloodstain patterns place attention on the scale of the patterns. The grid method involves setting up a grid of squares of known dimensions over the entire pattern using string and stakes (see Figure 19 ). All overall, medium-range, and close-up photographs are taken with and without the grid. The second method, called the perimeter ruler method , involves setting up a rectangular border of rulers around the pattern and then placing a small ruler next to each stain. In this method, the large rulers show scale in the overall and medium-range photos, whereas the small rulers show scale in the close-up photographs (see Figure 20 ). Some investigation teams use tags in close-up photographs to show evidence numbers or other details.

An area-of-origin determination may be calculated at the discretion of the bloodstain analyst when the circumstances of the case warrant such a determination.

Quick Review • Transfer patterns are created when an object with blood on it makes

simple contact with a surface or moves along a surface. The direction of movement may be shown by a feathering of the pattern.

• Flows may originate from a single drop or a large amount of blood. Because the direction of the fl ow is caused by gravity, the direction of a pattern may suggest the original position of the surface when the fl ow was formed.

• A pool is formed where large amounts of blood collect. The pool may be absorbed into the surface of deposition over time.

• The presence of skeletonization on a feathered bloodstain suggests that the stain was disturbed after the perimeter had had suffi cient time to dry.

• A drop trail pattern is separate from other patterns, and it is formed by a series of single blood droplets dripping off an object or injury.

String grid - Two-foot squares

= Lettered or numbered label in each square

FIGURE 19 The grid method may be used for photograph- ing bloodstain pattern evidence. Crime Scene Investigation & Reconstruction, 3rd ed., by R.R. Ogle, Jr. (Upper Saddle River, NJ: Prentice-Hall, 2011).

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BLOODSTAIN PATTERN ANALYSIS

Measurement rulers

Small metric rulers

Areas with bloodstain patterns

FIGURE 20 The perimeter ruler method may be used for photographing bloodstain pattern evidence. Crime Scene Investigation & Reconstruction, 3rd ed., by R.R. Ogle, Jr. (Upper Saddle River, NJ: Prentice-Hall, 2011).

CHAPTER REVIEW

• Individual bloodstains can convey to the bloodstain analyst the directionality and angle of impact of the blood when it impacted a surface. Bloodstain patterns may convey to the analyst the location of victims (who was bleeding) or sus- pects (who was causing the bleeding), the movement of bleeding individuals, and the number of blows delivered.

• Surface texture is of paramount importance in the interpre- tation of bloodstain patterns; rounder drops generally are produced on smooth, nonporous surfaces, whereas rough surfaces result in irregular-edged drops. However, correla- tions between standards and unknowns are valid only when identical surfaces are used.

• The direction of travel of blood that struck an object may be discerned by the stain’s shape. The pointed end of a blood- stain always faces its direction of travel.

• The angle of impact of an individual bloodstain can be ap- proximated by the degree of distortion or lengthening of the bloodstain, or it can be more effectively estimated using the width-to-length ratio of the stain.

• An impact spatter pattern occurs when an object impacts a source of blood. This produces forward spatter projected forward from the source and back spatter projected back- ward from the source.

• Impact spatter patterns can be classifi ed as low-velocity (�4 mm drops), medium-velocity (1–4 mm drops), or high- velocity (�1 mm drops) for descriptive purposes. These categories should not be used to assume what kind of force created the pattern.

• The area of convergence is the point on a two-dimensional plane from which the drops of an impact spatter pattern originated. This area can be estimated by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails.

• The area of origin of a bloodstain pattern is the area in three-dimensional space where blood was projected from, showing the position of the victim or suspect when the stain- producing event took place. The string method is commonly used at a crime scene to approximate the position of the area of origin.

• Gunshot spatter can consist of both forward spatter from an exit wound and back spatter from an entrance wound; however, only back spatter will be produced if the bullet does not exit the body.

• A cast-off pattern is created when a blood-covered object fl ings blood in an arc onto a nearby surface. This kind of

All measurements of stains and calculations of angle of impact and point of origin should be re- corded in crime-scene notes. Especially important stains can be roughly sketched within the notes.

Only some jurisdictions have a specialist on staff to decipher patterns either at the scene or from photographs at the lab. Therefore, it is important that all personnel be familiar with patterns to properly record and document them for use in reconstruction.

Quick Review • Photographs and sketches should fi rst be cre-

ated of the overall bloodstain pattern to show the orientation of the pattern to the scene.

• Medium-range and close-up photographs may use the grid method or perimeter ruler method to show the orientation and relative size of the pattern and individual stains. VIRTUAL LAB

Blood Spatter Evidence To perform a virtual blood spatter analysis, go to www.pearsoncustom.com/us/vlm/

252

pattern commonly occurs when a person pulls a bloody fi st or weapon back between delivering blows to a victim.

• The characteristic arterial spray spatter is created when a victim suffers an injury to a main artery or the heart, and the pressure of the continuing pumping of blood projects blood out of the injured area in spurts, which are apparent in the pattern.

• Expirated blood is expelled from the mouth or nose and may appear as very fi ne high-velocity spatter or large low-velocity bloodstain clusters. This kind of pattern may contain bubbles of oxygen or be mixed with saliva.

• A void pattern features an area free of spatter where an object (or person) blocked the deposition of blood spatter onto a surface or object. Because the spatter was deposited onto the object or person instead, the shape of the void may give a clue about the size and shape of the missing object or person.

• Transfer patterns are created when an object with blood on it makes simple contact with a surface or moves along a surface. The direction of movement may be shown by a feathering of the pattern.

• Flows may originate from a single drop or a large amount of blood. Because the direction of the fl ow is caused by gravity, the direction of a pattern may suggest the original position of the surface when the fl ow was formed.

• A pool is formed where large amounts of blood collect. The pool may be absorbed into the surface of deposition over time.

• The presence of skeletonization on a feathered bloodstain suggests that the stain was disturbed after the perimeter had had suffi cient time to dry.

• A drop trail pattern is separate from other patterns, and it is formed by a series of single blood droplets dripping off an object or injury.

• Photographs and sketches should fi rst be created of the over- all bloodstain pattern to show the orientation of the pattern to the scene.

• Medium-range and close-up photographs may use the grid method or perimeter ruler method to show the orientation and relative size of the pattern and individual stains.

REVIEW QUESTIONS

1. Violent contact between individuals at a crime scene fre- quently produces bleeding and results in the formation of ______________ .

2. The proper interpretation of bloodstain patterns necessitates carefully planned ______________ using surface materials comparable to those found at the crime scene.

3. Bloodstain patterns may convey to the analyst the location and movements of ______________ or ______________ during the commission of a crime.

4. True or False: Harder and less porous surfaces result in less spatter, whereas rough surfaces result in stains with more spatter and serrated edges. ______________

5. Generally, bloodstain diameter (increases/decreases) with height.

6. The ______________ and ______________ of blood strik- ing an object may be discerned by the stain’s shape.

7. A drop of blood that strikes a surface at an angle of impact of approximately 90 degrees will be close to (elliptical, circular) in shape.

8. The angle of impact of an individual bloodstain can be es- timated using the ratio of ______________ divided by ______________ .

9. ______________ is the most common type of blood spat- ter found at a crime scene and is produced when an object forcefully contacts a source of blood.

10. True or False: Forward spatter consists of the blood projected backward from the source, and back spatter is projected out- ward and away from the source. ______________

KEY TERMS

angle of impact

area of convergence

area of origin

arterial spray

back spatter

cast-off

drop trail pattern

expirated blood pattern

fl ow

forward spatter

high-velocity spatter

impact spatter

low-velocity spatter

medium-velocity spatter

satellite spatter

skeletonization

transfer pattern

void

BLOODSTAIN PATTERN ANALYSIS

253

11. The classifi cations of impact spatter based on the size of droplets and from the velocity of an applied force are ______________ , ______________ , and ______________ impact spatter.

12. True or False: The velocity of an applied force is a good way to classify impact patterns and to determine the kind of force that produced them. ______________

13. The ______________ is the point on a two-dimensional plane from which the drops originated.

14. The ______________ of a bloodstain pattern in a three- dimensional space illustrates the position of the victim or suspect when the stain-producing event took place.

15. The ______________ method is used at the crime scene to determine the area of origin.

16. A(n) ______________ is created by contact between a bloody object and a surface.

17. The pattern made by a bloody object dragged across a sur- face (lightens, darkens) as the object moves away from the point of contact.

18. True or False: Footwear transfer patterns created by an indi- vidual who was running typically show imprints with more space between them than those of an individual who was walking. ______________

19. True or False: The direction of a fl ow pattern may show move- ments of objects or bodies while the fl ow was still in prog- ress or after the blood had dried. ______________

20. The approximate drying time of a(n) ______________ of blood determined by experimentation is related to the en- vironmental conditions of the scene and may suggest how much time has elapsed since its deposition.

21. The edges of a bloodstain will generally ______________ within 50 seconds of deposition and be left intact even if the central area of a bloodstain is altered by a wiping motion.

22. A(n) ______________ pattern commonly originates from repeated strikes from weapons or fi sts and is characterized by an arc pattern of separate drops showing directionality.

23. True or False: Characteristics of a cast-off pattern arc cannot give clues about the kind of object that was used to produce the pattern. ______________

24. When an injury to an artery is suffered, the pressure of the continuing pumping of blood projects blood out of the injured area in spurts, creating a pattern known as ______________ .

25. If a(n) ______________ pattern is found at a scene, it may show movement, lead to a discarded weapon, or provide identifi cation of the suspect by his or her own blood.

26. A bloodstain pattern created by ______________ features bubbles of oxygen in the drying drops and may be lighter in color than impact spatter.

27. The shape and size of the blank space, or ______________ , created when an object blocks the deposition of spatter onto a surface and is then removed may give a clue about the size and shape of the missing object or person.

28. True or False: Each bloodstain pattern found at a crime scene should be noted, studied, and photographed. ______________

29. When documenting bloodstain patterns, the ____________ involves setting up a grid of squares of known dimensions over the entire pattern and taking overview, medium-range, and close-up photographs with and without the grid.

30. The ______________ method of bloodstain documentation involves setting up a border of rulers around the pattern and then placing a small ruler next to each stain to show relative position and size in photographs.

31. True or False: The pointed end of a bloodstain always faces toward its direction of travel. ______________

BLOODSTAIN PATTERN ANALYSIS

254

BLOODSTAIN PATTERN ANALYSIS

APPLICATION AND CRITICAL THINKING

1. After looking at the bloodstains in the fi gure, answer the following questions:

a) Which three drops struck the surface closest to a 90-degree angle? Explain your answer.

b) Which three drops struck the surface farthest from a 90-degree angle? Explain your answer.

c) In what direction were drops 2 and 7 traveling when they struck the surface? Explain your answer.

2. Investigator Priscilla Wright arrives at a murder scene and fi nds the body of a victim who suffered a gunshot wound, but she doesn’t see any blood spatter on the wall or fl oor behind it. What should she conclude from this observation?

3. Investigator Terry Martin arrives at an assault scene and fi nds a cast-off pattern consisting of tiny droplets of blood in a very linear arc pattern on a wall near the victim. What does this tell him about the weapon used in the crime?

1. 2.

5. 6.

7. 8.

9.

3. 4.

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Computer Forensics

From Chapter 18 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

THE BTK KILLER Dennis Rader was arrested in February 2005 and charged with committing ten murders since 1974 in the area around Wichita, Kansas. The BTK killer, whose nickname stands for “bind, torture, kill,” hadn’t murdered since 1991, but resurfaced in early 2004 when he sent a letter to a local newspaper taking credit for a 1986 slaying. Included with the letter were a photocopy of the victim’s driver’s license and three photos of her body. The BTK killer was back to his old habit of taunting the police.

Three months later another letter surfaced. This time the letter detailed some of the events sur- rounding BTK’s fi rst murder victims. In 1974, he had strangled Joseph and Julie Otero along with two of their children. Shortly after commit- ting those murders, BTK had also sent a letter to a local newspaper in which he gave himself the name BTK. In December 2004, a package found in a park contained the driver’s license of another BTK victim along with a doll whose hands were bound with pantyhose and that was covered with a plastic bag.

The major break in the case came when BTK sent a message on a fl oppy disk to a lo- cal TV station. “Erased” information on the disk was recovered and restored by forensic computer specialists, and the disk was traced to the Christ Lutheran Church in Wichita. The disk was then quickly linked to Dennis Rader, the church council president. The long odyssey

of searching for the BTK killer was fi nally over. LEARNING OBJECTIVES After studying this chapter, you should be able to: • List and describe the hardware and software components

of a computer. • Understand the difference between read-only memory and

random-access memory. • Describe how a hard disk drive is partitioned. • Describe the proper procedure for preserving computer

evidence at a crime scene. • Understand the difference between and location of visible

and latent data. • List the areas of the computer that will be examined to

retrieve forensic data. • Relate various areas found on the computer where a user’s

Internet activities can be investigated. • Describe how e-mails, chat, and instant messages on the

Internet can be traced and recovered. • List and describe three locations where investigators may

pinpoint the origin of a hacker. • Describe the types of services offered by modern mobile

devices, such as cell phones, and the potential investigative value they have.

Computer Forensics

Andrew W. Donofrio

© Jeff Tuttle/epa/Corbis All Rights Reserved © Jeff Tuttle/epap /Corbis All Rigghts Reserved

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S ince the 1990s, few fi elds have progressed as rapidly as computer technology. Computers are no longer a luxury, nor are they in the hands of just a select few. Technology and electronic data are a part of everyday

life and permeate all aspects of society. Consequently, computers have become increasingly important as sources of evidence in an ever-widening spectrum of criminal activities. Moreover, on the corporate side, issues of regulatory compliance, such as HIPPA and Sarbanes Oxley, and problems of employee misconduct have made IT investigations and data forensics a necessary com- ponent of a company’s security program.

Police investigators frequently encounter computers and other digital devices in all types of cases. As homicide investigators sift for clues, they may inquire, for example, whether the method for a murder was researched on the Internet, whether signs of an extramarital affair can be found in e-mails or remnants of instant messages (which may provide a motive for a spouse kill- ing or murder for hire), or whether threats were communicated to the victim before a murder by an obsessed stalker. Arson investigators may want to know whether fi nancial records on a computer show a motive for an arson-for-profi t fi re. A burglary investigation would certainly be aided if law enforcement could show that the proceeds from a theft were being sold online—perhaps through eBay or a similar online auction site.

In addition, the use of computers poses some threats of its own. The accessibility of computers to children and the perception of anonymity in online interactions has given sexual predators a way to seek out child victims online. The vulnerability of computers to hacker attacks is a constant reminder of security issues surrounding digitally stored data. Finally, the fact that computers control most of our critical infrastructure makes technology an appetizing target for would-be terrorists.

Computer forensics involves the preservation, acquisition, extraction, analysis, and interpretation of computer data. Although this is a simple defi nition, it gets a bit more complicated. Part of this complication arises from technology itself. More and more devices are capable of storing electronic data: cell phones, personal digital assistants (PDAs), iPods, digital cameras, fl ash memory cards, smart cards, jump drives, and many others. Further complicating matters is the cross-pollination of devices. Cell phones now have the same capabilities of per- sonal computers, and personal computers are often used to facilitate commu- nications. Methods for extracting data from these devices each present unique challenges. However, sound forensic practices apply to all these devices. The most logical place to start to examine these practices is with the most common form of electronic data: the personal computer.

From Input to Output: How Does the Computer Work? HARDWARE VERSUS SOFTWARE

Before we get into the nuts and bolts of computers, we must establish the important distinction between hardware and software. Hardware comprises the physical components of the computer: the computer chassis, monitor,

hardware The physical components of a computer: case, keyboard, monitor, motherboard, RAM, HDD, mouse, and so on; generally speaking, if it is a computer component you can touch, it is hardware.

Andrew W. Donofrio is a retired detective lieutenant from the prosecutor’s offi ce in Bergen County, New Jersey, and is a leading computer forensics examiner for Bergen County, with more than twenty-three years experience in the fi eld of law enforcement. He has conducted hundreds of forensic examinations of computer evidence and frequently lectures on the subject throughout the state, as well as teaching multiday courses on computer forensics and investigative topics at police academies, colleges, and corporations throughout the United States. Mr. Donofrio now owns Cyberology consultants, which provides IT investigation, computer and network forensic, and business continuity and disaster recovery planning services.

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keyboard, mouse, hard disk drive, random-access memory (RAM), central processing unit (CPU), and so on (see Figure 1 ). The list is extensive, but gen- erally speaking, if it is a computer component or peripheral that you can see, feel, and touch, then it is hardware.

Software , conversely, is a set of instructions compiled into a program that  performs a particular task. Software consists of programs and applica- tions that carry out a set of instructions on the hardware. Operating systems (e.g., Windows, Mac OS, Linux, Unix), word-processing programs (e.g., Micro- soft Word, WordPerfect), web-browsing applications (e.g., Internet Explorer, Safari, Firefox), and accounting applications (e.g., Quicken, QuickBooks, Microsoft Money) are all examples of software.

It is important not to confuse software with the physical media that it comes on. When you buy an application such as Microsoft Offi ce, it comes on a compact disc (CD). The CD containing this suite of applications is typically referred to as software, but this is technically wrong. The CD is external computer media that contains the software; it is a container for a set of instructions and a medium from which to load the instructions onto the hard disk drive (i.e., the hardware).

HARDWARE COMPONENTS

COMPUTER CASE/CHASSIS The case is the physical box holding the fi xed internal computer components in place. Cases come in many shapes and sizes: a full upright tower chassis, a slim model sitting on a desktop, or an all-in-one monitor/computer case like the iMac. For our purposes, the term system unit is probably most appropriate when describing a chassis seized as evidence. The term system unit accurately references the chassis, including the motherboard and other internal components.

FIGURE 1 Cutaway diagram of a personal computer showing the tangible hardware components of a computer system. Courtesy Tim Downs

software A set of instructions compiled into a program that performs a particular task; software consists of programs and applications that carry out a set of instructions on the hardware.

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POWER SUPPLY The term power supply is actually a misnomer because it doesn’t actually supply power—the power company does that. Rather, a com- puter’s power supply converts power from the wall outlet to a usable format for the computer and its components. Different power supplies have different wattage ratings. The use or, more specifi cally, the components of the com- puter dictate the appropriate power supply.

MOTHERBOARD The main circuit board in a computer (or other electronic device) is referred to as the motherboard . Motherboards contain sockets for chips and slots for add-on cards. Examples of add-on cards are the video card to connect the computer to the monitor, a network card or modem to connect to an internal network or the Internet, and a sound card to connect to speakers. Sockets on the motherboard typically accept things like random- access memory (RAM) or the central processing unit (CPU). The keyboard, mouse, CD-ROM drives, fl oppy disk drives, monitor, and other peripherals or components connect to the motherboard in some fashion through a wired or wireless connection.

SYSTEM BUS Contained on the motherboard, the system bus is a vast, complex network of wires that carry data from one hardware device to another. This network is analogous to a complex highway. Data is sent along the bus in the form of ones and zeros (or, to be accurate, as electrical impulses representing an “on” or “off” state); this two-state form of data is known as binary computing .

READ-ONLY MEMORY (ROM) This rather generic term describes special chips on the motherboard. ROM chips store programs called fi rmware , used to start the boot process and confi gure a computer’s components. Today’s ROM chips, termed fl ash ROM , are a combination of two types of chips used in past motherboard technologies. The fi rst was known as the system ROM , which was responsible for booting the system and handling the “assumed” system hardware present in the computer. As the system ROM, generally speak- ing, could not be altered, and because as technology matured changes to the “ assumed” hardware were more common, a different type of chip was intro- duced. The complementary metal-oxide semiconductor (CMOS) was a separate chip that allowed the user to exercise setup control over several system com- ponents. Regardless of how this technology is present on the motherboard, it can be referred to as the BIOS, for basic input-output system . The operation of the BIOS is relevant to several computer forensic procedures, particularly the boot sequence. It is the set of routines associated with the BIOS in ROM that initiates the booting process and enables the computer to communicate with various devices in the system such as disk drives, keyboard, monitor, and printer. As this chapter will make clear, it is important not to boot the actual computer under investigation to the original hard disk drive. This would cause changes to the data, thus compromising the integrity of evidence. The BIOS allows investigators to control the boot process to some degree.

CENTRAL PROCESSING UNIT (CPU) The central processing unit (CPU) , also re- ferred to as a processor, is essentially the brain of the computer. It is the main (and typically the largest) chip that plugs into a socket on the motherboard. The CPU is the part of the computer that actually computes. Basically, all operations performed by the computer are run through the CPU. The CPU carries out the program steps to perform a requested task. That task can range from opening and working in a Microsoft Word document to performing advanced mathe- matical algorithms. CPUs come in various shapes, sizes, and types. Intel Pentium chips and Advanced Micro Devices (AMD) chips are among the most common.

RANDOM-ACCESS MEMORY (RAM) This is one of the most widely mentioned types of computer memory. Random-access memory (RAM) takes the burden

motherboard The main system board of a computer (and many other electronic devices), which delivers power, data, and instructions to the computer’s components; every component in the computer connects to the motherboard, either directly or indirectly.

central processing unit (CPU) The main chip within the computer, also referred to as the brain of the computer, which handles most of the operations (i.e., code and instructions) of the computer.

random-access memory (RAM) The volatile memory of a computer, where programs and instructions that are in use are stored; when power is turned off, its contents are lost.

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off the computer’s processor and hard disk drive (HDD). If the computer had to access the HDD each time it wanted data, it would run slowly and ineffi ciently. Instead the computer, aware that it may need certain data at a moment’s no- tice, stores the data in RAM. It is helpful to envision RAM as chips that create a large spreadsheet, with each cell representing a memory address that the CPU can use as a reference to retrieve data. RAM is referred to as volatile memory because it is not permanent; its contents undergo constant change and are lost once power is taken away from the computer. RAM takes the physical form of chips that plug into the motherboard; SIMMs (single inline memory modules), DIMMs (dual inline memory modules), and SDRAM (synchronous dynamic random-access memory) are just a few of the types of chips. Today’s computers come with varying amounts of RAM: 2 to 4 GB (gigabytes) is the most common capacity. 1

INPUT DEVICES Input devices are used to get data into the computer or to give the computer instructions. Input devices constitute part of the “user” side of the computer. Examples include the keyboard, mouse, joystick, and scanner.

OUTPUT DEVICES Output devices are equipment through which data is obtained from the computer. Output devices are also part of the “user” side of the com- puter, and provide the results of the user’s tasks. They include the monitor, printer, and speakers.

HARD DISK DRIVE (HDD) Generally speaking, the hard disk drive (HDD) is the primary component of storage in the personal computer (see Figure 2 ). It typi- cally stores the operating system (e.g., Windows, Mac OS, Linux, or Unix), the programs (e.g., Microsoft Word, Internet Explorer, Open Offi ce for Linux, etc.) and data fi les created by the user (i.e., documents, spreadsheets, accounting information, the company database, etc.). Unlike RAM, the HDD is permanent storage and retains its information even after the power is turned off. HDDs work off a controller that is typically part of the motherboard, but sometimes take the form of an add-on (expansion) card plugged into the motherboard. The most common types of HDD controllers are integrated drive electronics

hard disk drive (HDD) Typically the main storage location within the computer, which consists of magnetic platters contained in a case (usually 3.5” long in a desktop computer and 2.5” in a laptop) and is usually where the operating system, applications, and user data are stored.

FIGURE 2 An inside view of the platter and read/write head of a hard disk drive. Corbis RF

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(IDE), small computer system interface (SCSI), and serial ATA (SATA). Each HDD type has a different interface that connects it to the controller. Regard- less of the type of controller, the data is stored in basically the same fashion. HDDs are mapped, or formatted, and have a defi ned layout. They are logically divided into sectors, clusters, tracks, and cylinders (see the section Storing and Retrieving Data).

PUTTING IT ALL TOGETHER

A person approaches the computer, sits down, and presses the power button. The power supply wakes up and delivers power to the motherboard and all of the hardware connected to the computer. At this point the fl ash ROM chip on the motherboard (the one that contains the BIOS) conducts a power-on self test (POST) to make sure everything is working properly.

The fl ash ROM also polls the motherboard to check the hardware that is attached and follows its programmed boot order, thus determining from what device it should boot. Typically the boot device is the HDD, but it can also be a CD or USB drive. If it is the HDD, the HDD is then given control. It locates the fi rst sector of its disk (known as the master boot record), determines its layout (i.e., (partition[s]), and boots an operating system (e.g., Windows, Mac OS, Linux, or Unix). The person is then presented with a computer work environment, commonly referred to as a desktop.

Now ready to work, the user double-clicks an icon on the desktop, such as a Microsoft Word shortcut, to open the program and begin to type a document. The CPU processes this request, locates the Microsoft Word program on the HDD (using a predefi ned map of the drive called a fi le system table ), carries out

CLOSER ANALYSIS OTHER COMMON STORAGE DEVICES

Although the HDD is the most common storage device for the personal computer, many others exist. Methods for storing data and the layout of that data can vary from device to device. A CD-ROM, for example, uses a different technology and format for writing data than a smart media card or USB thumb drive. Fortunately, regardless of the differences among devices, the same basic forensic principles apply for acquiring the data. Common storage devices include the following:

CD-R/RW (Compact Disc—Record/Rewrite) and DVD-R/RW (DVD— Record/Rewrite) Compact discs (CDs) and digital video discs (DVDs) are two of the most common forms of external data storage. They are used to store a wide variety of information, such as music, video, and data fi les. They are discs made largely of plastic, with an aluminum layer that is read by laser light in a CD/DVD reader. Blu-Ray discs have also emerged in the market offering larger storage capacity than their pre- decessor optical media. In addition to larger storage capacities, Blu-Ray discs are read by a blue laser light instead of the red laser that reads CDs and DVDs. Different optical media are encoded in different ways, making the job of the forensic examiner diffi cult at times.

USB Thumb Drives and Smart Media Cards These devices can store a large amount of data—some as much as 64 GB. They are

known as solid-state storage devices because they have no moving parts. Smart media cards are typically found in digital cameras, mobile devices, and PDAs, but USB thumb drives come in many shapes, sizes, and storage capacities.

Tapes Tapes come in many different formats and storage capacities. Each typically comes with its own hardware reader and, sometimes, a proprietary application to read and write its contents. Tapes and thumb drives are typically used for backup purposes and consequently have great forensic potential.

Network Interface Card (NIC) Very rarely does one encounter a computer today that doesn’t have a NIC. Whether they are on a local network or the Internet, when computers need to communicate with each other, they typically do so through a NIC. NICs come in many different forms: add-on cards that plug into the motherboard, hard-wired devices on the motherboard, add-on cards (PCMCIA) for laptops, and universal serial bus (USB) plug-in cards, to name a few. Some are wired cards, meaning they need a physical wired connection to participate on the network, and others are wireless, meaning they receive their data via radio waves.

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operating system (OS) The software that provides the bridge between the system hardware and the user; the OS lets the user interact with the hardware and manages the fi le system and applications. Some examples are Windows (XP, Vista, and Windows 7), Linux, and Mac OS.

partition A contiguous set of blocks that are defi ned and treated as an independent disk.

the programming instructions associated with the application, loads Microsoft Word into RAM via the system bus, and sends the output to the monitor by way of the video controller, which is either located on or attached to the motherboard.

The user then begins to type, transferring data from the keyboard into RAM. When fi nished, the user may print the document or simply save it to the HDD for later retrieval. If printed, the data is taken from RAM, processed by the CPU, placed in a format suitable for printing, and sent through the system bus to the external port where the printer is connected. If the document is saved, the data is taken from RAM, processed by the CPU, passed to the HDD controller (i.e., IDE, SCSI, or SATA) by way of the system bus, and written to a portion of the HDD. The HDD’s fi le system table is updated so it knows where to retrieve that data later. In actuality, the boot process is more complex than this, and the forensic examiner must possess an in-depth knowledge of the process.

The preceding example illustrates how three components perform most of the work: the CPU, RAM, and system bus. The example can get even more complicated as the user opens more applications and performs multiple tasks simultaneously (i.e., multitasks ). Several tasks can be loaded into RAM at once, and the CPU is capable of juggling them all. This allows for a multitasking en- vironment and the ability to switch back and forth between applications. All of this is orchestrated by the operating system and is written in the language of the computer—ones and zeros. The only detail missing, one that is important from a forensic standpoint, is a better understanding of how data is stored on the hard disk drive. This is discussed next.

Quick Review • Computer forensics involves preserving, acquiring, extracting, and inter-

preting computer data. • Software programs are applications that carry out a set of instructions. • The central processing unit (CPU) is the brain of the computer—the main

chip responsible for doing the actual computing. • The motherboard is the main circuit board within a computer. • Read-only memory (ROM) chips store programs that control the boot

(startup) process and confi gure a computer’s components. • Random-access memory (RAM) is volatile memory, which is frequently

lost when power is turned off. Programs are loaded into RAM because of its faster read speed.

• The hard disk drive (HDD) is typically the primary location of data storage within the computer.

Storing and Retrieving Data Before beginning to understand how data is stored on a hard disk drive (HDD), it is fi rst important to understand the role of the operating system (OS) . An OS, such as Windows, Mac OS, Linux, or Unix, is the bridge between the human user and the computer’s electronic components. It provides the user with a working environment and facilitates interaction with the system’s components. Each OS supports certain types of fi le systems that store data in different ways.

FORMATTING AND PARTITIONING THE HDD

Generally speaking, before an OS can write to an HDD, it must fi rst be formatted. But even before it can be formatted, a partition must be defi ned. A partition is nothing more than a contiguous set of blocks that are defi ned and treated

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as an independent disk. This means that a hard disk drive can hold several partitions, making a single HDD appear as several disks.

Partitioning a drive can be thought of as dividing a container that begins as nothing more than six sides. We then cut a hole in the front of the container and insert two drawers and the hardware required to open and close them. We have just created a two-drawer fi ling cabinet and defi ned each drawer as contiguous blocks of storage. A partitioning utility such as Disk Manager or fdisk defi nes the drawer or drawers (i.e., partitions) that will later hold the data on the HDD. Just as the style, size, and shape of fi ling cabinet drawers can vary, so too can partitions.

After a hard drive is partitioned, typically it is formatted. (At this point this would be high-level formatting, not to be confused with low-level formatting, which is generally done by the manufacturer of the HDD.) The formatting pro- cess initializes portions of the HDD and creates the structure of the fi le system. The fi le system can be thought of as the system for storing and locating data on a storage device. Some of the fi le system types are FAT12 (typically on fl oppy disks), FAT16 (older DOS and older Windows partitions), FAT32 (Windows fi le systems), NTFS (most current Windows systems—2008 Windows 7, and XP), EXT2 and EXT3 (Linux systems), and HPFS (some Macintosh systems).

Each of these fi le systems has a different way of storing, retrieving, and allocating data. In summary, a drive is prepared in three processes: low-level formatting (typically done by the manufacturer, dividing the platters into tracks and sectors), partitioning (accomplished through a utility such as fdisk or Disk Manager, defi ning a contiguous set of blocks), and formatting (i.e., initializing portions of the disk and creating the fi le system structure). The process is a bit more technical and detailed than this, but at the conclusion of these basic steps, the drive is logically defi ned. (We say “logically” because no real divisions are made. That is, if you were to crack open the HDD before or after partitioning and formatting, to your naked eye the platters would look the same.)

MAPPING THE HDD

As shown in Figure 3 , HDDs contain several plat- ters stacked vertically that are logically divided into sectors, clusters, tracks, and cylinders. Sectors are typically 512 bytes in size (a byte is eight bits; a bit is a single one or zero). (Currently, work is being done on hard disk drives with increased minimum sec- tor sizes, in an effort to increase drive performance. However, at this time 512 bytes is still the standard for most hard disk drives.) Clusters are groups of sectors; their size is defi ned by the fi le system, but they are always in sector multiples of two. (Although an NTFS partition does permit a one-sector- per-cluster scenario, such a scenario is not usually chosen.) A cluster, therefore, consists of two, four, six, or eight sectors, and so on. (With modern fi le systems, the user can exercise some control over the number of sectors per cluster.) Tracks are concentric circles that are defi ned around the platter. Cylinders are groups of tracks that reside directly above and below each other.

Additionally, the HDD has a fi le system table, or map, of the layout of the defi ned space in that parti- tion. FAT fi le systems use a fi le allocation table (which

byte A group of eight bits.

sector The smallest addressable unit of data by a hard disk drive; generally consists of 512 bytes.

Sector 1

Cluster

Sector 2

Cylinder

Track

Shaft

FIGURE 3 Partitions of a hard disk drive.

bit Short for binary digit ; taking the form of either a one or a zero, it is the smallest unit of information on a machine.

cluster A group of sectors in multiples of two; cluster size varies from fi le system to fi le system and is typically the minimum space allocated to a fi le.

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is where the acronym FAT comes from) to track the location of fi les and fold- ers (i.e., data) on the HDD, whereas NTFS fi le systems (used by most cur- rent Windows systems—Vista, XP, and Windows 7) use, among other things, a master fi le table (MFT) . Each fi le system table tracks data in different ways, and computer forensic examiners should be versed in the technical nuances of the HDDs they examine. It is suffi cient for our purposes here, however, to merely visualize the fi le system table as a map where the data is located. This map uses the numbering of sectors, clusters, tracks, and cylinders to keep track of the data.

One way to envision a partition and fi le system is as a room full of safe- deposit boxes. The room itself symbolizes the entire partition, and the boxes symbolize clusters of data. In order to determine who rented which box, and where each renter’s property is, a central database is needed. This would be es- pecially necessary if a person rented two boxes located in opposite ends of the room (this would be noncontiguous data on the HDD). The database tracking the locations of the safe-deposit boxes is much like a fi le system table tracking the location of data within the clusters.

This example is also useful for understanding the concept of reformatting an HDD. If the database managing the locations of the safe-deposit boxes were wiped out, the property in them would still remain; we just wouldn’t know what was where. It is the same with the hard disk drive. If a user were to wipe the fi le system table clean—for example, by reformatting it—the data itself would not be gone. Both the database tracking the locations of the safe-deposit boxes and the fi le system table tracking the location of the data in the cluster are maps— they are not actual contents. (Exceptions exist with some fi le systems, such as an NTFS fi le system, which stores data for very small fi les right in its fi le system table, known as the master fi le table).

Quick Review • The computer’s operating system (OS) is the bridge between the human

user and the computer’s electronic components. It provides the user with a working environment and facilitates interaction with the system’s components.

• Formatting is the process of preparing a hard disk drive to store and retrieve data in its current form.

• A sector is the smallest unit of data that a hard drive can address. A clus- ter usually is the minimum space allocated to a fi le. Clusters are groups of sectors.

• A FAT is a fi le allocation table. It tracks the location of fi les and folders on the hard disk drive.

Processing the Electronic Crime Scene Processing the electronic crime scene has a lot in common with processing a traditional crime scene. The investigator must fi rst ensure that the proper legal requirements (e.g., search warrant, consent, etc.) have been met so that the scene can be searched and the evidence seized. The investigator should then devise a plan of approach based on the facts of the case and the physi- cal location. The scene should be documented in as much detail as possible before disturbing any evidence and before the investigator lays a fi nger on any computer components. Of course, there are circumstances in which an investigator may have to act quickly and pull a plug before documenting the scene, such as when data is in the process of being deleted.

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DOCUMENTING THE CRIME SCENE

Typical crime-scene documentation is accomplished through two actions: sketching and photographing. The electronic crime scene is no different. First, the scene should be sketched in the style of a fl oor plan (see Figure 4 ), and then overall photographs of the location should be taken. In the case of a network, a technical network sketch should also be included if possible.

After photographs have been taken of the overall layout, close-up photographs should be shot. A close-up photograph of any running computer monitor should be taken. All the connections to the main system unit, such as peripheral devices (e.g., keyboard, monitor, speakers, mouse, etc.), should be photographed. If necessary, system units should be moved delicately and carefully to facilitate the connections photograph (see Figure 5 ). Close-up photographs of equipment serial numbers should be taken if practical.

FIGURE 4 Rough sketch made at a crime scene with necessary measurements included.

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LIVE COMPUTER

ACQUISITION

At this point, investigators must decide whether to perform a live acquisition of the data, perform a system shutdown (as in the case of server equip- ment), pull the plug from the back of the computer, or do a combination of these things. Pulling the plug should always be done by removing the plug from the back of the computer. If the plug is re- moved from the wall, a battery backup (UPS) might be in place, causing an alert to the system and keeping the unit “ powered on.” Several factors in- fl uence this decision. For example, if encryption is being used and by pulling the plug the data will en- crypt, rendering it unreadable without a password or key, pulling the plug would not be prudent. Similarly, if crucial evidentiary data exists in RAM and has not been saved to the HDD, the data will be lost. Hence, if power to the system is discontinued, another option must be considered. Regardless, the

equipment will most likely be seized. Exceptions exist in the corporate envi- ronment, where servers are fundamental to business operations.

A computer can be found in several states. Among these is live (i.e., running or powered on) and dead (i.e., not running or powered off). The traditional ap- proach for dealing with a live, running computer in computer forensics was to pull the plug from the back. By doing this, the examiner froze the data in time, thus preventing any additions or modifi cations to the hard disk drive contained within. Although this methodology still has its limited place, several traits of today’s computer technology and some evidentiary considerations necessitate consideration of performing a live examination prior to disconnecting power. By examining one of many instances in which a live examination might be considered, we can get a good view of how this process works.

Let’s say an investigator responds to the scene of a missing 14-year-old girl. The investigator notices a laptop computer on a desk in the girl’s bed- room. Closer scrutiny reveals that the laptop is live and what appears to be an instant message conversation is on the screen. Additionally, what can be seen of the conversation discusses a meeting with what appears to be an older man. The investigator needs to start the process of identifying the individual in the conversation. Almost simultaneously, the investigator needs to preserve the evidence that probably exists only in RAM. Here a consideration of “order of volatility” must be made. The fact that the investigator needs to work with the computer system means that changes to the data (i.e., the electronic crime scene) will be made. Considering order of volatility allows the investigator to develop a sequence of steps that will limit the effects of each change on the subsequent steps and collection methods, thus affording the collection of the greatest amount of unaltered evidentiary data. In this example steps might be completed in the following order:

1. Photograph all sections of the conversation screen to document the conversation in the same form the user sees. Merely scrolling through the conversation to afford photographing the entire conversation is minimally intrusive and limited (and arguably inconsequential) changes will occur.

2. Depending on his or her own skill level, the investigator may want to acquire the contents of RAM at this point. This would be accomplished by running a controlled application that the investigator already possesses

FIGURE 5 Back of a computer showing all connections.

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and that is designed for such a purpose. Of course, the resulting content needs to be written somewhere, and it should not be written to the com- puter’s hard drive. Rather, the examiner should use a clean piece of media that can handle the size of the output. There are several options for this.

3. Next, the investigator may want to consider copying the text and pasting it to a new document or utilizing a save command in the chat application to save the conversation in text format. Again, this conversation should not be saved to the hard dive of the system being examined.

4. If the investigator feels that encryption is being used, he or she may consider imaging the entire hard drive in this live environment. Because shutting the computer with an encryption in place renders the hard drive’s contents unreadable without a password, it may be a good idea to get an image of the hard drive while it is still decrypted. This requires special response tools and external media that can handle the large image size.

This is just one way to approach this and other live examinations. The order of steps can also be debated among forensic examiners. The following questions are important for the forensic examiner to consider:

1. What is the type of case I am investigating? 2. What is the evidence I seek? 3. How best can I completely acquire that evidence without contaminating

other aspects of the “electronic crime scene”? 4. In what order should I take those steps? (order of volatility) 5. Do I have the training, education, experience, equipment, and tools to

accomplish this, or do I need assistance?

Finally, the only perfect crime scene is one that has not been entered. The min- ute investigators enter a crime scene there will be changes to the environment, but obviously, entering the physical crime scene is a necessary function of evi- dence collection. Processing it should be done in a certain order so that, for example, the collection of fi ngerprints won’t prevent the proper collection of blood, hair, fi ber, and so on. The same applies to the electronic crime scene.

After the photographs and sketches are com- plete and, if appropriate, the live examination has been performed, but before disconnecting the peripherals from the computer, a label should be placed on the cord of each peripheral, with a cor- responding label placed on the port to which it is connected. A numbering scheme should be de- vised to further identify each system unit if several computers are at the scene ( Figure 6 ). The combi- nation of sketching, photographing, and labeling should adequately document the scene, prevent fu- ture confusion about which component went with which system unit, and facilitate reconstruction if necessary for lab or courtroom purposes.

FORENSIC IMAGE

ACQUISITION

Now that the items have been seized, the data needs to be obtained for analysis. The number of electronic items that potentially store evidentiary data are too vast to cover in this section. The hard disk drive will be used as an example, but the same “best practices” principles apply for other electronic devices as well.

2A

4A 3A

8A

7A

1A

1A

8A

FIGURE 6 Back of a computer with each component correlated with its port through the use of a labeling scheme.

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Throughout the entire process, the computer forensic examiner must use the least intrusive method. The goal in obtaining data from an HDD is to do so with- out altering even one bit of data. Because booting an HDD to its operating system changes many fi les and could potentially destroy evidentiary data, obtaining data is generally accomplished by removing the HDD from the system and plac- ing it in a laboratory forensic computer so that a forensic image can be created. However, the BIOS of the seized computer sometimes interprets the geometry of the HDD differently than the forensic computer does. In these instances, the image of the HDD must be obtained using the seized computer. Regardless, the examiner must ensure that the drive to be analyzed is in a “write-blocked,” or read-only, state when creating the forensic image. Furthermore, the examiner needs to be able to prove that the forensic image he or she obtained includes every bit of data and caused no changes, or writes, to the HDD.

To this end, a sort of fi ngerprint of the drive is taken before and after imag- ing. This fi ngerprint is taken through the use of a Message Digest 5 (MD5)/ Secure Hash Algorithm (SHA) , or similar validated algorithm. Before im- aging the drive the algorithm is run and a 32-character alphanumeric string is produced based on the drive’s contents. The algorithm is then run against the resulting forensic image; if nothing changed, the same alphanumeric string is produced, thus demonstrating that the image is all-inclusive of the original contents and that nothing was altered in the process.

A forensic image of the data on an HDD (as well as on fl oppy disks, CDs, DVDs, tapes, fl ash memory devices, and any other storage medium) is merely an exact duplicate of the entire contents of the drive. In other words, all portions of the drive are copied, from the fi rst bit (i.e., one or zero) to the last. Why would investigators want to copy what appears to be blank or unused portions of the HDD? The answer is simple: to preserve latent data, which is discussed later in the chapter. It suffi ces to say here that data exists in areas of the drive that are, generally speaking, unknown and inaccessible to most end users. This data can be valuable as evidence. Therefore, a forensic image—one that copies every single bit of information on the drive—is necessary. A forensic image differs from a backup or standard copy in that it takes the entire contents, not only data the operating system is aware of.

Many forensic software packages come equipped with a method for ob- taining the forensic image. The most popular software forensic tools— EnCase, Forensic Toolkit (FTK), Forensic Autopsy (Linux-based freeware), and SMART (Linux-based software by ASR Data)—all include a method for obtaining a forensic image. All produce self-contained image fi les that can then be inter- preted and analyzed. They also allow image compression to conserve storage. The fact that forensic imaging results in self-contained, compressed fi les allows many images from different cases to be stored on the same forensic storage drive. This makes case management and storage much easier (see Figure 7 ).

Quick Review • Aspects of a computer that should be photographed close up at an electronic

crime scene include (1) the screen of any running computer monitor; (2) all the connections to the main system unit, such as peripheral devices (e.g., key- board, monitor, speakers, mouse, etc.); and (3) equipment serial numbers.

• Evidentiary considerations may require the investigator to perform a live examination prior to disconnecting power.

• Two situations in which an investigator would not unplug a computer at an electronic crime scene are (1) if encryption is suspected, and thus pulling the plug would reencrypt the data, rendering it unreadable without a password or key, and (2) if data exists in RAM that has not been saved to the HDD and will thus be lost if power to the system is discontinued.

Message Digest 5 (MD5)/ Secure Hash Algorithm (SHA) A software algorithm used to “fi ngerprint” a fi le or contents of a disk; used to verify the integrity of data. In forensic analysis it is typically used to verify that an acquired image of suspect data was not altered during the process of imaging.

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• The primary goal in obtaining data from an HDD is to do so without alter- ing even one bit of data. To this end, a Message Digest 5 (MD5)/Secure Hash Algorithm (SHA) takes a “fi ngerprint” of a hard disk drive (HDD) before and after forensic imaging.

Analysis of Electronic Data Analysis of electronic data is virtually limitless and bound only to the level of skill of the examiner. The more familiar an examiner is with computers, operat- ing systems, application software, data storage, and a host of other disciplines, the more prepared he or she will be to look for evidentiary data.

Because computers are vast and complex, discussing each area, fi le, direc- tory, log, or computer process that could potentially contain evidentiary data is beyond the scope of one chapter—and may be beyond the scope of an entire book. What follows are some of the more common areas of analysis. While reading this section, refl ect on your own knowledge of computers and consider what other data might be of evidentiary value and where it might be found.

VISIBLE DATA

The category of visible data includes all information that the operating system is presently aware of and thus is readily accessible to the user. Here we present sev- eral common types of visible data considered in many investigations. This list is by no means exhaustive and can include any information that has value as evidence.

DATA/WORK PRODUCT FILES One place to fi nd evidence is in documents or fi les produced by the suspect. This category is extremely broad and can include

visible data All data that the operating system is presently aware of and thus is readily accessible to the user.

FIGURE 7 Screen shot of EnCase software. EnCase is a common forensic software application capable of imaging and assisting in the analysis of data. Courtesy EnCase, www.encase.com

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swap fi le A fi le or defi ned space on the HDD used to conserve RAM; data is swapped, or paged, to this fi le or space to free RAM for applications that are in use.

data from just about any software program. Microsoft Word and WordPerfect word-processing programs typically produce text-based fi les such as typed documents and correspondence. These programs, and a host of other word- processing programs, have replaced the typewriter. They are common sources of evidence in criminal cases, particularly those involving white-collar crime.

Also relevant in white-collar crime and similar fi nancial investigations are any data related to personal and business fi nance. Programs such as QuickBooks and Peachtree accounting packages can manage the entire fi nan- cial portion of a small to midsize business. Similarly, it is not uncommon to fi nd personal bank account records in the computer that are managed with personal fi nance software such as Microsoft Money and Quicken. Moreover, criminals sometimes use these programs as well as spreadsheet applications to track bank accounts stolen from unsuspecting victims. Computer foren- sic examiners should familiarize themselves with these programs, the ways in which they store data, and methods for extracting and reading the data.

Advances in printer technology have made high-quality color printing both affordable and common in many homes. Although this is a huge benefi t for home offi ce workers and those interested in graphic arts, the technology has been used for criminal gain. Counterfeiting and check and document fraud are easily perpetrated on most home computers. All that is required is a decent ink-jet printer and a scanner. Including the computer, a criminal could set up a counterfeiting operation for less than $1500. Examiners must learn the graphics and photo-editing applications used for nefarious purposes. Being able to recognize the data produced by these applications and knowing how to display the images is key to identifying this type of evidence.

SWAP FILE DATA When an application is running, the program and the data being accessed are loaded into RAM. A computer’s RAM is much faster than the “read” speed of the hard disk drive, and that’s why the programs are loaded here—for fast access and functioning. RAM, however, has its limits. Some computers have a gigabyte or two of RAM, and still others as much as four to eight gigabytes. Regardless of the amount, though, most operating systems (Windows, Linux, and so on) are programmed to conserve RAM when possible. This is where the swap fi le comes in. The operating system attempts to keep only data and applications that are presently being used in RAM. Other applications that were started, but are currently waiting for user attention, may be swapped out of RAM and written to the swap space on the hard disk drive. 2

For example, a manager of a retail store may want to type a quarterly report based on sales. The manager starts up Microsoft Word and begins his report. Needing to incorporate sales fi gures from a particular spreadsheet, he opens Microsoft Excel. Depending on what is running on the computer, the original Word document may be swapped from RAM to the swap space on the HDD to free up space for Excel. As the manager goes back and forth between the pro- grams (and maybe checks his e-mail in between) this swapping continues. Data that is swapped back and forth is sometimes left behind in the swap space. Even as this area is constantly changed, some of the data is orphaned in unallocated space, an area of the HDD discussed later in this chapter.

A swap fi le or space can be defi ned as a particular fi le or even a separate HDD partition, depending on the operating system and fi le system type (e.g., FAT, NTFS, EXT2, etc.). For Windows systems either the swap fi le Win386.sys or pagefi le.sys is used, depending on the specifi c Windows version and fi le sys- tem type. Linux and current Mac OS systems can create partitions just for swap- ping data in and out of RAM. Data in the swap space can be read by examining the HDD through forensic software or a utility that provides a binary view, such as Norton Disk Editor or WinHex (see Figure 8 ).

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TEMPORARY FILES Any user who has suffered a sudden loss of power in the middle of typing a document can attest to the value of a temporary fi le . Most programs automatically save a copy of the fi le being worked on in a temporary fi le. After typing a document, working on a spreadsheet, or working on a slide presentation, the user can save the changes, thus promoting the temporary copy to actual fi le status. Temporary fi les are created as a sort of backup on the fl y. If the computer experiences a sudden loss of power or other catastrophic failure, the temporary fi le can be recovered, limiting the amount of data lost. The loss is limited, but not altogether prevented, because the temporary fi le is not updated in real time. Rather, it is updated periodically, depending on the application’s settings. The default interval in most programs is every ten minutes.

Temporary fi les can sometimes be recovered during a forensic examination. Additionally, some of the data that may have been orphaned from a previous version may be recoverable, if not the complete fi le. This is true even when a document has been typed and printed but never saved. The creation of the tem- porary fi le makes it possible for some of this “unsaved” data to be recovered during analysis.

Another type of temporary fi le valuable to the computer investigator is the print spool fi le. When a print job is sent to the printer, a spooling process de- lays the sending of the data to the printer. This happens so the application can continue to work while the printing takes place in the background. To facilitate this, a temporary print spool fi le is created; this fi le typically includes the data to be printed and information specifi c to the printer. There are different meth- ods for accomplishing this, and thus the fi les created as a result of this process vary. It is sometimes possible to view the data in a readable format from the fi les created during the spooling process.

LATENT DATA

The term latent data includes data that is obfuscated (not necessarily intentionally) from a user’s view. It includes areas of fi les and disks that are typically not apparent to the computer user but that contain data nonetheless.

RAM module (chip)

Swap space

Swapping of data between RAM and the hard drive's swap space or page file

FIGURE 8 As a user switches between applications and performs multiple tasks, data is swapped back and forth between RAM and the computer’s hard drive. This area on the hard drive is referred to as either swap space or a paging fi le.

temporary fi les Files temporarily written by an application to perform a function or to provide a “backup” copy of a work product should the computer experience a catastrophic failure.

latent data Areas of fi les and disks that are typically not apparent to the computer user (and often not to the operating system) but contain data nonetheless.

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fi le slack The area that begins at the end of the last sector that contains logical data and terminates at the end of the cluster.

Latent data is one of the reasons a forensic image of the media is created. If a standard copy were all that is produced, only the logical data (i.e., that which the operating system is aware of) would be captured. Getting every bit of data ensures that potentially valuable evidence in latent data is not missed.

Once the all-inclusive forensic image is produced, how is the latent data viewed? Utilities that allow a user to examine a hard disk drive on a binary (ones and zeros) level are the answer. Applications such as Norton Disk Editor and WinHex provide this type of access to a hard disk drive or other computer media. Thus these applications, sometimes also referred to as hex editors (for the hexadecimal shorthand of computer language), allow all data to be read on the binary level independent of the operating system’s fi le system table. Utilities such as these can write to the media under examination, thus changing data. Consequently, a software or hardware write-blocker should be used.

A more common option in data forensics is to use specialized forensic examination software. EnCase and Forensic Toolkit for Windows and SMART and Forensic Autopsy for Linux are examples of forensic software. Each allows a search for evidence on the binary level and provides automated tools for per- forming common forensic processing techniques. Examiners should be cau- tious, however, about relying too heavily on automated tools. To merely use an automated tool without understanding what is happening in the background and why evidentiary data may exist in particular locations would severely im- pede the investigator’s ability to testify to the fi ndings.

SLACK SPACE Slack space is empty space on a hard disk drive created because of the way the HDD stores fi les. Recall that, although the smallest unit of data is one bit (either a one or a zero), an HDD cannot address or deal with such a small unit. In fact, not even a byte (eight bits) can be addressed. Rather, the smallest unit of addressable space by an HDD is the sector. HDDs typically assign sectors in 512-byte increments, whereas CD-ROMs allocate 2,048 bytes per sector.

If the minimum addressable unit of the HDD is 512 bytes, what happens if the fi le is only 100 bytes? In this instance there are 412 bytes of slack space. It does not end here, however, because there is also minimum cluster requirement. As you may recall, clusters are groups of sectors used to store fi les and folders. The cluster is the minimum storage unit defi ned and used by the logical partition. It is because of the minimum addressable sector of the HDD and the minimum unit of storage requirement of the volume that we have slack space.

Minimum cluster allocation must be defi ned in sectors in multiples of two. Thus, a cluster includes two, four, six, or eight sectors or more. Returning to our initial example of the 100-byte fi le, suppose an HDD has a two- sectors-per- cluster volume requirement. This means that the HDD will allocate a minimum of two 512-byte sectors (a total of 1,024 bytes) of storage space for that 100-byte fi le. The remaining 924 bytes would be slack space (see Figure 9 ).

To illustrate this point, let us expand on the previous example of safe-deposit boxes. The bank offers safe-deposit boxes of a particular size. This is the equiva- lent of the HDD’s clusters. A person wanting to place only a deed to a house in the box gets the same size box as a person who wants to stuff it full of cash. The former would have empty space should he or she desire to place additional items in the box. This empty space is the equivalent of slack space. But what if the box becomes full and the person needs more space? That person must then get a second box. Similarly, if a fi le grows to fi ll one cluster and beyond, a second cluster is allocated. The remaining space in the second cluster is slack space. This continues as more and more clusters are allocated to accommodate the size of the growing fi le.

There are actually two types of slack space: RAM slack and fi le slack. Ram slack occupies the space from where the actual (i.e., logical) data portion of the fi le ends to where the fi rst allocated sector in the cluster terminates. File slack ,

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therefore, occupies the remaining space of the cluster. RAM slack is a concept that was more relevant in older operating systems. Remember that the mini- mum amount of space the HDD can address is the 512-byte sector. Therefore, if the fi le size is only 100 bytes, the remaining space must be padded. Some older operating systems pad this area with data contained in RAM. This could in- clude webpages, passwords, data fi les, or other data that existed in RAM when the fi le was written. Modern Windows operating systems pad this space with zeros, but some examinations may still yield valuable data in this area.

Let us go back to the 100-byte fi le with the two-sectors-per-cluster minimum requirement. Following the end of the logical data (i.e., beyond the 100 bytes), the remaining 412 bytes of that sector is RAM slack; the additional 512 bytes completing the cluster is then fi le slack. See Figure 10 for a visual depiction. The question now becomes, What can I expect to fi nd in slack space, and why is this important? The answer: Junk—valuable junk.

HDD

Cluster 1024 Bytes

Sector (512 Bytes)

Sector (512 Bytes)

D A T A

Slack Space (924 Bytes)

100 Bytes

File Data

FIGURE 9 Slack space illustrated in a two-sector cluster. Cluster sizes are typically greater than two sec- tors, but two sectors are displayed here for simplicity.

HDD

Cluster 1024 Bytes

Sector (512 Bytes)

Sector (512 Bytes)

412 512

D A T A

RAM Slack 0's or Data from RAM

File Slack (Orphaned Data)

100 Bytes

FIGURE 10 File slack.

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Data occupying sectors that the operating system is aware of

Unallocated space

FIGURE 11 A simplistic view of a hard drive platter demonstrating the concept of unallocated space.

File slack, on the other hand, can contain a lot of orphaned data. To illustrate this point, let’s take the 100-byte fi le example a bit further. Let’s say that before the 100-byte fi le was written to the HDD, occupying one cluster (two sectors totaling 1,024 bytes), a 1,000-byte fi le occupied this space but was deleted by the user. When a fi le is “deleted,” the data still remains behind, so it is probably a safe bet that data from the original 1,000-byte fi le remain in the slack space of the new 100-byte fi le now occupying this cluster. This is just one example of why data exists in fi le slack and why fi le slack may be valuable as evidence.

In one fi nal attempt to illustrate this point, let us again build on our safe-deposit box analogy. Suppose a person rents two safe-deposit boxes, each box representing a sector and the two combined representing a cluster. If that person places the deed to her house in the fi rst box, the remaining space in that box would be analogous to RAM slack. The space in the second box would be the equivalent of fi le slack. The only difference is that, unlike the empty spaces of the safe-deposit box, the slack space of the fi le probably contains data that may be valuable as evidence.

The data contained in RAM and fi le slack is not really the concern of the operating system. As far as the OS is concerned, this space is empty and therefore ready to be used. Until that happens, however, an examination with one of the aforementioned tools will allow a look into these areas, thus revealing the orphaned data. The same is true for unallocated space.

UNALLOCATED SPACE Latent evidentiary data also resides in unallocated space . What is unallocated space, how does data get in there, and what is done to access this space? If we have an 80 GB hard drive and only half of the hard drive is fi lled with data, then the other half, or 40 GB, is unallocated space (see Figure 11 ). Returning to our safe-deposit box analogy, if the entire bank of safe- deposit boxes contains 100 boxes, but only 50 are currently in use, then the other 50 would be the equivalent of unallocated space. The HDD’s unallocated space typically contains a lot of useful data. The constant shuffl ing of fi les on the HDD causes data to become orphaned in unallocated space as the logical

unallocated space The unused area of the HDD that the operating system fi le system table sees as empty (i.e., containing no logical fi les) but that may contain old data.

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portion of the fi le is rewritten to other places. Some examples of ways in which data can become orphaned are through fragmentation, during the creation of swap fi les or swap space, or in the process of deleting fi les.

DEFRAGMENTING Defragmenting an HDD involves moving noncontiguous data back together. Remember that the HDD has minimum space reservation requirements. Again, if the fi le requires only 100 bytes of space, the operat- ing system may allocate much more than that. If the fi le grows past what has been allocated for it, another cluster is required. If, however, a different fi le occupies the next cluster in line, then the operating system will have to fi nd another place for that additional data on the drive. In this scenario, the fi le is said to be fragmented because data for the same fi le is contained in noncon- tiguous clusters. In the case of the HDD, the shuffl ing of fi les causes data to be orphaned in unallocated space.

Ultimately fragmentation of numerous fi les can degrade the performance of an HDD, causing the read/write heads to have to traverse the platters to locate the data. Defragmenting the HDD rearranges noncontiguous data into contiguous clusters. Building yet again on our safe-deposit box analogy, if our renter eventually needs to store more property than her original box can hold, the bank will rent her a second box. If, however, all the boxes around hers are occupied and the only free one is in another section of the room, then her property is “fragmented.” The bank would have to “defrag” the safe-deposit boxes to get the property of users with more than one box into adjacent boxes.

SWAP FILE/SWAP SPACE Recall that a computer uses the HDD to maximize its amount of RAM by constantly swapping data in and out of RAM to a predetermined location on the HDD, thus freeing valuable RAM. The constant read and write operations of RAM cause a constant change in the swap fi le— WIN386.swp or pagefi le.sys —in Windows or in the swap space on a Linux system. Data can become orphaned in unallocated space from this constant swapping to and from the HDD.

DELETED FILES The deletion of fi les is another way that data becomes or- phaned in unallocated space. Data from deleted fi les can manifest itself in dif- ferent ways during a forensic examination. The actions that occur when a fi le is deleted vary among fi le systems. What is fairly consistent, though, is that generally the data is not truly removed. For example, consider what happens when a user or program deletes a fi le in a Windows operating system with a FAT fi le system. When a fi le is deleted, the fi rst character in the fi le’s directory entry (i.e., in its name) is replaced with the Greek letter sigma. When the sigma replaces the fi rst character, the fi le is no longer viewable through conventional methods and the operating system views the space previously occupied by the fi le as available. The data, however, is still there.

This example doesn’t account for the actions of the Windows Recycle Bin. When the Windows operating system is set up to merely place the deleted fi le in the Recycle Bin, the original directory entry is deleted and one is created in the Recycle folder for that particular user. The new Recycle folder entry is linked to another fi le, the info or info2 fi le, which includes some additional data, such as the location of the fi le before its deletion should the user wish to restore it to that location. Detailed discussions of the function of the Recycle Bin are beyond the scope of this chapter, but suffi ce it to say that, even when the Recycle Bin has been “emptied,” the data usually remains behind until overwritten. Although Windows NTFS partitions and Linux EXT partitions handle deleted fi les differently, in both cases the data typically remains.

What if a new fi le writes data to the location of the original fi le? Generally speaking, the data is overwritten. This is, of course, unless the new fi le only partially overwrites the original: If a fi le that occupied two clusters is deleted,

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and a new fi le overwrites one of the clusters, then the data in the second cluster is orphaned in unallocated space. Of course, yet a third fi le can overwrite the second cluster entirely, but until then the data remains in unallocated space.

Let us once again look to our safe-deposit box analogy. If, for example, the owner of two safe-deposit boxes stopped renting them, the bank would list them as available. If the owner didn’t clean them out, the contents would remain unchanged. If a new owner rented one of the boxes, the contents from the former owner would be replaced with the new owner’s possessions. The second box would therefore still contain orphaned contents from its previ- ous owner. The contents would remain in this “unallocated box” until another renter occupies it.

Quick Review • The types of computer evidence can be grouped under two major sub-

headings: visible and latent data. • Visible data is data that the operating system is aware of, and thus is eas-

ily accessible to the user. It includes any type of user-created data, such as word-processing documents, spreadsheets, accounting records, data- bases, and pictures.

• Temporary fi les created by programs as a sort of on-the-fl y backup can prove valuable as evidence. Data in the swap space used to conserve valu- able RAM within the computer system can also yield evidentiary data.

• Latent data is data that the operating system is not aware of. The constant shuffl ing of data through deletion, defragmentation, swapping, and so on, is one of the reasons data is stored in latent areas.

• Latent data can exist in both RAM slack and fi le slack. RAM slack is the area from the end of the logical fi le to the end of the sector. File slack is the remaining area from the end of the fi nal sector containing data to the end of the cluster.

• Latent data might be found in unallocated space—space on an HDD that the operating system sees as empty and ready for data.

• When a user deletes fi les, the data typically remains behind, so deleted fi les are another source of latent data.

Forensic Analysis of Internet Data It’s important from the investigative standpoint to be familiar with the evi- dence left behind regarding a user’s Internet activity. A forensic examination of a computer system reveals quite a bit of data about a user’s Internet activity. The data described next would be accessed and examined using the forensic techniques outlined in the previous sections of this chapter.

INTERNET CACHE

Evidence of web browsing typically exists in abundance on the user’s com- puter. Most web browsers (e.g, Internet Explorer and Firefox) use a caching system to expedite web browsing and make it more effi cient. This was particu- larly true in the days of dial-up Internet access. When a user accesses a web- site, such as the New York Times home page, the data is fed from that server (in this example, that of the New York Times ), via the Internet service provider and over whatever type of connection the user has, to his or her computer. If that computer is accessing the Internet via a dial-up connection, the transfer of the New York Times home page may take a while because the data trans- fer rate and capabilities (bandwidth) of the telephone system is limited. Even

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with the high-speed access of a fi ber or cable connection, conservation of bandwidth is always a consideration. Taking that into account, web browsers store, or cache, portions of the pages visited on the local hard disk drive. This way, if the page is revisited, portions of it can be reconstructed more quickly from this saved data, rather than having to use precious bandwidth to pull it yet again from the Internet.

This Internet cache is a potential source of evidence for the computer investigator. Portions of, or in some cases entire, visited webpages can be reconstructed. For security purposes, modern Internet browsers take steps to clear out, or erase, the web cache. But in some cases, even after having been deleted, these cached fi les can be recovered (see the section on deleted data). Investigators must know how to search for this data within the particular web browser used by a suspect.

INTERNET COOKIES

Cookies provide another area where potential evidence can be found. To ap- preciate the value of cookies you must fi rst understand how they get onto the computer and their intended purpose. Cookies are placed on the local hard disk drive by websites the user has visited, if the user’s web browser (such as Internet Explorer) is set to allow this to happen. Microsoft Internet Explorer places cookies in a dedicated directory. Websites use cookies to track certain information about its visitors. This information can be anything, such as his- tory of visits, purchasing habits, passwords, and personal information used to recognize the user for later visits.

Consider a user who registers for an account at the Barnes and Noble bookstore website, then returns to the same site from the same computer a few days later. The site will then display “Welcome, [ User Name ].” This data was retrieved from the cookie fi le placed on the user’s hard disk drive by the website during the initial visit and registration with the site.

It is helpful to think of cookies almost like a caller ID for websites. The site recognizes and retrieves information about the visitor, as when a salesperson recognizes a caller from a caller ID display and quickly pulls the client’s fi le. Cookie fi les can be a valuable source of evidence. In Internet Explorer, they take the form of plain text fi les, which can typically be opened with a standard text viewer or word-processing program. The existence of the fi les themselves, regardless of the information contained within, can be of evidentiary value to show a history of Web visits. A typical cookie may resemble the following: [email protected]. From this we can surmise that someone using the local computer login rsaferstein accessed the forensic science website. It is possible that the cookie was placed there by an annoying pop-up ad, not a website the user visited, but considered against other evidence in the computer data, the presence of a particular cookie may have corroborative value.

INTERNET HISTORY

Most web browsers track the history of webpage visits for the computer user. This is probably done merely for convenience. Like the “recent calls” list on a cell phone, the Internet history provides an accounting of sites most recently visited, with some storing weeks’ worth of visits. Users can go back and access sites they recently visited just by going through the browser’s history. Most web browsers store this information in one particular fi le; Internet Explorer uses the index.dat fi le. On a Windows system, an index.dat fi le is created for each login user name on the computer.

The history fi le can be located and read with most popular computer foren- sic software packages. It displays the uniform resource locator (URL) of each

Internet cache Portions of visited webpages placed on the local hard disk drive to facilitate quicker retrieval when the webpage is revisited.

cookies Files placed on a computer from a visited website that are used to track visits to and usage of that site.

Internet history An accounting of websites visited; different browsers store this information in different ways.

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FIGURE 13 Bookmarks or favorite places can be saved for quick access in most web browsers. Copyright © 2013 by Pearson Education, Inc. Microsoft ® and Windows ® are registered trademarks of the Microsoft Corporation in the USA and other countries. Screen shots and icons reprinted with permission from the Microsoft Corporation. This text is not sponsored or endorsed by or affi liated with the Microsoft Corporation.

website, along with the date and time the site was accessed. An investigation involving Internet use almost always includes an examination of Internet history data.

In some respects, the term Internet history is wrong be- cause it doesn’t encompass all of these fi les’ functions. Several browsers—Internet Explorer, for one—store other valuable evidence independent of Internet access. It is not uncommon to see fi les accessed over a network listed in the history. Similarly, fi les accessed on external media, such as CDs or thumb drives, may also appear in the history. Regardless, the Internet history data is a valuable source of evidence worthy of examination (see Figure 12 ).

BOOKMARKS AND FAVORITE PLACES

Another way users can access websites quickly is to store them in their book marks or Favorite Places. Like presetting radio stations, web browsers allow users to bookmark websites for future visits (see Figure 13 ). A lot can be learned from a user’s bookmarked sites. You may learn what online news a person is interested in or what type of hobbies he or she has. You may also see that person’s favorite child pornography or computer hacking sites bookmarked.

In Internet Explorer the favorite places are kept in a folder with link fi les, or shortcuts, to particular URLs. They can be or- ganized in subfolders or grouped by type. The same is true for the Firefox web browser, except that Firefox bookmarks are stored in a document written in hypertext markup language (HTML), the same language interpreted by the web browsers themselves.

FIGURE 12 The Internet history displays more than just web-browsing activity. Here we see Microsoft Word documents and a picture accessed on the current day.

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Quick Review • Places where a forensic computer examiner might look to determine what

websites a computer user has visited recently are the Internet cache, cook- ies, and the Internet history.

• The history fi le can be located and read with a forensic software package. Another way to access websites that have been visited is by examining bookmarks and favorite places

Forensic Investigation of Internet Communications Computer investigations often begin with or are centered on Internet commu- nication. Whether it is a chat conversation among many people, an instant mes- sage conversation between two individuals, or the back-and-forth of an e-mail exchange, human communication has long been a source of evidentiary material. Regardless of the type, investigators are typically interested in communication.

ROLE OF THE IP

With all of the computer manufacturers and software developers out there, some common rules are necessary for computers to be able to communicate on a global network. Just as any human language needs rules for communication to be successful, so does the language of computers. Computers that participate on the Internet, therefore, must be provided with an address known as an Internet protocol (IP) address from the Internet service provider to which they connect.

IP addresses take the form ###.###.###.###, in which, generally speaking, ### can be any number from 0 to 255. A typical IP address might look like this: 66.94.234.13. Not only do IP addresses provide the means by which data can be routed to the appropriate location, but they also provide the means by which most Internet investigations are conducted (see Figure 14 ). Thus the IP

bookmark A feature that enables the user to designate favorite sites for fast and easy access.

Internet

Two computer users chatting.

Verizon Internet service provider

America Online Internet service provider

Assigned IP address: 206.46.255.12 Assigned IP address: 64.12.255.102

FIGURE 14 Two computers communicating by sending data to each other’s IP address via the Internet. An IP address is assigned to each computer by its respective Internet service provider. Richard Saferstein, Ph.D.

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COMPUTER FORENSICS

address may lead to the identity of a real person. If an IP address is the link to the identity of a real person, then it is quite obviously valuable for identifying someone on the Internet.

To illustrate, let’s assume that a user of the Internet, fi ctitiously named John Smith, connects to the Internet from his home by way of a Verizon FIOS connection. Verizon in this case would be responsible for providing Smith with his IP address. Verizon was issued a bank of IP addresses with which to service its customers from a regulatory body designed to track the usage of IP addresses (obviously so no one address is used by two different users at the same time).

Suppose that Smith, while connected to the Internet, decides to threaten an ex-girlfriend by sending her an e-mail telling her he is going to kill her. That e-mail must fi rst pass through Smith’s Internet service provider’s routers (in this case, Verizon’s) on its way to its destination—Smith’s girlfriend. The e-mail would be stamped by the servers that it passes through, and this stamp would include the IP address given to Smith by Verizon for his session on the Internet.

An investigator responsible for tracking that e-mail would locate the originating IP address stamped in the e-mail header. That IP address could be researched using one of many Internet sites (e.g., www.centralops.net ) to determine which Internet service provider was given this IP as part of the block it was assigned for serving its customers. The investigator then fi les a subpoena with the Internet service provider (i.e., Verizon) asking which of its customers was using that IP address on that date and time.

IP addresses are located in different places for different methods of Internet communications. E-mail has the IP address in the header portion of the mail. This may not be readily apparent and may require a bit of confi guration to reveal. Each e-mail client is different and needs to be evaluated on a case-by-case basis. For an instant message or chat session, the provider of the chat mechanism— AOL, Yahoo, and so on—would be contacted to provide the user’s IP address.

E-MAIL, CHAT, AND INSTANT MESSAGING

E-mail fi les can be read by a number of clients , or software programs. Two of the most popular ways to access, read, and store e-mail in today’s Internet environment, however, are Microsoft Outlook and through an Internet browser. Some people even use a combination of the two.

If an e-mail account is linked through Microsoft Outlook, then the e-mail is stored in a compound fi le (i.e., a fi le with several layers). Typically, compound fi les exist for received e-mail (i.e., the inbox), sent e-mail, and deleted e-mail. Users can also create new categories (shown as folders in Outlook) and cat- egorize saved e-mail there. Most computer forensic software applications can view, or mount, these compound fi les so that the e-mail can be seen, includ- ing any fi le attachments. These fi les can also be imported into a clean copy of Microsoft Outlook (i.e., one not attached to an account), and the e-mail can be viewed there. Investigators must also be aware that, in a computer network environment, the user’s Outlook fi les may not reside on his or her workstation computer but rather on a central mail or fi le server.

Most accounts offer the ability to access e-mail through a web-based interface as well. This way, users can access their e-mail remotely from other computers. For e-mail accessed through a web browser, the information presented earlier on Internet-based evidence applies. The Web interface converts the e-mail into a document suitable for reading in a web browser. Consequently, web-based e-mail is sometimes found in the Internet cache. This is particularly true of free Internet e-mail providers such as Hotmail and Yahoo.

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Much of the evidence from Internet communication is also derived from chat and instant message technology. This is particularly true in the world of child sexual exploitation over the Internet. Various technologies provide chat and instant messaging services. Most chat and instant message conversations are not saved by the parties involved. Although most of the software does allow for conversation archiving, it is typically turned off by default. Therefore, conversations of this nature typically exist in the volatile memory space of random-access memory (RAM).

Recall that RAM is termed volatile because it holds data only while the computer has power. Unplugging the computer will cause the data located in RAM to be lost. If, however, chat or instant message conversations occurred that are relevant as evidence, even if the computer was turned off, thus eras- ing the data in RAM, all may not be lost. Remember that there is an interaction between the computer system’s RAM and the hard disk drive. RAM is a com- modity, and therefore the computer’s operating system makes an effort to con- serve it as much as possible. This is done by swapping/paging that information back and forth into the swap space or paging fi le. Therefore remnants of chat conversations are often found in the swap space or paging fi le during a foren- sic examination of the hard disk drive. These remnants, however, are typically fragmented, disconnected, and incomplete. Therefore, if the chat or instant message is still present on the screen (and thus probably still in RAM), the in- vestigator needs a method by which to preserve and collect it.

A detailed discussion of capturing volatile data from RAM is beyond the scope of this chapter, but considerations for dealing with a live (running) computer have been discussed in the section Live Computer Acquisition in this chapter. Note that several commercial forensic software packages can capture this data. Similarly, Linux-based tools can accomplish this as well. The examiner may even be able to export the data remotely to another device. Regardless of the method, the data must be acquired.

Furthermore, many programs such as AOL Instant Messenger, Yahoo Messenger, and mIRC (Internet Relay Chat) create fi les regarding the rooms or channels a user chatted in or the screen names with which a user sent instant messages. Each application should be researched, and the computer forensic examination should be guided by an understanding of how each functions.

HACKING

Unauthorized computer intrusion, more commonly referred to as hacking , is the concern of every computer administrator. Hackers penetrate computer systems for a number of reasons. Sometimes the motive is corporate espio- nage; other times it is merely for bragging rights within the hacker commu- nity. Most commonly, though, a rogue or disgruntled employee with some knowledge of the computer network is looking to cause damage. Whatever the motivation, corporate America frequently turns to law enforcement to in- vestigate and prosecute these cases.

Generally speaking, when investigating an unauthorized computer intru- sion, investigators concentrate their efforts in three locations: log fi les , vola- tile memory , and network traffi c . Logs typically document the IP address of the computer that made the connection. Logs can be located in several loca- tions on a computer network. Most servers on the Internet track connections made to them through the use of logs. Additionally, the router (i.e., the device responsible for directing data) may contain log fi les detailing connections.

Similarly, devices known as fi rewalls may contain log fi les listing computers that were allowed (or that merely attempted) access to the net- work or an individual system. Firewalls are devices (taking the form of either hardware or software) that permit only requested traffi c to enter a computer

Webextra 1

Follow the Trail of an E-mail as It Travels Through the Internet www.mycrimekit.com

hacking Frequently used as a slang term for performing an unauthorized computer or network intrusion.

fi rewall Hardware or software designed to protect intrusions into an Internet network.

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COMPUTER FORENSICS

system or, more appropriately, a network. In other words, if a user didn’t send out a request for Internet traffi c from a specifi c system, the fi rewall should block its entry unless previously confi gured to allow that traffi c through. If the log fi les have captured the IP address of the intruder, then revealing the user behind the IP is the same process as for e-mail. Investigating a computer intrusion, however, does get a bit more complicated.

Frequently, in cases of unlawful access to a computer network, the perpe- trator attempts to cover the tracks of his or her IP address. In these instances, advanced investigative techniques may be necessary to discover the hacker’s true identity. When an intrusion is in progress, the investigator may have to capture volatile data, or data in RAM. The data in RAM at the time of an in- trusion may provide valuable clues to the identity of the intruder or, at least, about his or her method or tools of attack. As in the case of an instant message or chat conversation, the data in RAM needs to be acquired.

Another standard tactic for investigating intrusion cases is to document all programs installed and running on a system in order to discover any additional malicious software installed by the perpetrator to facilitate entry. The investigator uses specialized software to document running processes, registry entries, open ports, and any installed fi les.

Additionally, the investigator may want to capture live network traffi c as part of the evidence-collection and investigation process. Traffi c that travels the network does so in the form of data packets. In addition to data, these packets also contain source and destination IP addresses. If the attack requires two-way communication, as in the case of a hacker stealing data, then data needs to be transmitted back to the hacker’s computer using the destination IP address. Once this is learned, the investigation can focus on that system. However, care must be taken to ensure that the destination IP address does not belong to an unwitting and previously compromised computer under the control of the hacker. Moreover, the type of data that is being transmitted on the network may be a clue to what type of attack is being launched; whether any important data is being stolen; or what types of malicious software, if any, are involved in the attack.

Quick Review • IP addresses take the form ###.###.###.###, in which, generally speaking,

### can be any number from 0 to 255 • IP addresses provide the means by which data can be routed to the

appropriate location, and they also provide the means by which most Internet investigations are conducted

• An investigator tracking the origin of an e-mail seeks out the sender’s IP address in the e-mail’s header. Chat and instant messages are typically located in a computer’s random-access memory (RAM).

• Tracking the origin of unauthorized computer intrusions, or hacking, requires investigating a computer’s log fi le, RAM, and network traffi c.

• A fi rewall is a device designed to protect against intrusions into a computer network.

Mobile Forensics This section could just as well be titled Cell Phone Forensics, but because of the technological advances in mobile technology, handheld devices are much more than just phones. There truly has been cross-pollination between traditional computers and cell phones. In addition to traditional cell phone

284

COMPUTER FORENSICS

services, mobile devices offer many services that are offered by computers and other devices. These devices can provide a vast amount of useful and evidentiary data in an investigation.

The list of services available for mobile devices, although comprehensive, is certainly not exhaustive. It should be apparent, however, that aside from size and structure, little distinction can be made between the services offered by a computer system and those of a mobile device. As such, forensic examinations of mobile devices have much in common with computer forensics, at least in principal. Although there is a great deal of standardization in the computer market, the same is not true in the world of mobile devices. The operating systems that run mobile devices vary from manufacturer to manufacturer and device to device. Moreover, their inherent remote capabilities and constant connection and communication with service providers make collection and preservation diffi cult.

Recall from our early discussion that one of the principal goals in electronic evidence collection and analysis is to avoid alteration of data. With mobile devices, which are constantly registering their location with the service provider and potentially receiving GPS location updates, protecting against alteration is challenging. Compounded by the fact that many mobile devices offer remote kill and clear capabilities, investigators have their hands full. It may seem logical to merely shut the mobile device off to preserve data, but this is typically not recommended because it can clear out unsaved data exist- ing in volatile memory (much like a computer’s RAM contents).

Leaving the mobile device running but placing it in something that will block its communication is the preferred method. A Faraday shield is frequently used

CLOSER ANALYSIS

The following is a list of the more common services available on today’s mobile devices, along with several examples of the potential evidentiary value they hold:

1. Short Message Service (SMS)—Text Messaging Text mes- sages are another form of communication. They can be used to establish a link between two people simply by showing they have “ messaged” each other. There have been cases where a person has entered a business to commit robbery while a lookout re- mains in a vehicle parked outside, and text messages were used to communicate between the two.

2. Multimedia Message Service (MMS) Can be thought of as text messaging with attachments such as video clips, sound fi les, or pictures. In one particular case, an individual took a video of himself sexually assaulting an incapacitated girl, and then sent the video clip to friends via MMS.

3. Contact Lists and Call History The names, phone numbers, addresses, and/or e-mail addresses of people who are associated with the owner of the mobile device and the log of recent contacts he or she has had are generally available and are of use in an investigation.

4. Calendars, Appointments, and Tasks This information may pro- vide evidence of a suspect’s actions on a particular date.

5. Internet Access / Internet History / Internet Communication Much like a traditional computer, Internet activity can be of great evidentiary value. For example, it may link a suspect to a specifi c social networking site or screen name in a child sexual exploitation case. Often, mobile devices contain the same I nternet artifacts as computers, such as cookies, browser history, and bookmarks.

6. Digital Camera / Video There have been numerous cases where individuals have exploited this technology to take sur- reptitious, candid photographs of unsuspecting women in malls and stores.

7. E-mail Full e-mail access and clients (i.e., e-mail software) are available on most mobile devices, offering another source of potential evidence.

8. Global Positioning System (GPS) and Map Data Many de- vices, such as the Droid and iPhone, offer full GPS capabilities. The information in these applications can be extremely valuable in documenting the travel history of a suspect.

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COMPUTER FORENSICS

for mobile device evidence collection. Such a shield, often designed by mobile forensics manufacturers, will prevent the device from communicating (in or out) with the service provider. It has also been observed that other devices, such as the type of unlined paint can typically used for collecting arson-related evidence, can work as well. However, the effectiveness of alternatives should be tested in advance.

Another consideration in the collection of these devices is maintaining power so that the device can be transported, stored, and ultimately analyzed. Mobile forensics manufacturers provide battery devices that can be used to keep a unit running while it is being transported to the lab. The investigator, if possible, should always seize the mobile device’s charger and any associated cables. Because of the lack of standardization mentioned earlier, chargers and cables vary greatly between devices, and it is nearly impossible for examiners to stock every one.

Ultimately, data from the mobile device must be extracted and analyzed. Unlike computer forensics, however, the approach to mobile devices is more complicated. This complication arises because of the divergent ways that dif- ferent devices store and manage data. Moreover, manufacturers vary in the type of memory used to store data, involving a combination of expansion cards and internal memory structures (RAM/ROM). Similarly, operating systems vary between devices. The Motorola Droid, for example, uses the Google’s Android Operating System, while today’s iPhone uses Apple’s iPhone operat- ing systems, typically referred to as iOS. The two vary in their partition, fi le, and directory structure. These are just two of the overwhelming number of devices on the market and thus encountered by investigators. Consequently, mobile device examiners need a multitude of equipment and a signifi cant amount of knowledge.

There are numerous approaches to mobile forensics data extraction and analysis. Extraction of data can be done on the physical level, generally afford- ing the greatest amount of total data collection but also, at times, presenting challenges in analysis. Extraction can also be done on a logical level, which limits the data acquired, but the data is often easier to analyze. The examiner generally makes these determinations based on the type of case, evidence sought, his or her own training, and the technological limitations of the mobile device or the tools available for analysis. It is the experience of most mobile forensic examiners that a lab needs to be equipped with several varied tools for acquisition and analysis.

Quick Review • Mobile devices offer many of the services that are offered by computers

and other devices. These devices can provide a vast amount of useful and evidentiary data in an investigation.

• Leaving a mobile device running but placing it in something that will block its communication is the preferred method for preserving data on a mobile device.

• Complications arise in extracting and evaluating data from mobile devices because of the variety of ways that different devices store and manage data.

286

CHAPTER REVIEW • Computer forensics involves preserving, acquiring, extracting,

and interpreting computer data.

• Software programs are applications that carry out a set of instructions.

• The central processing unit (CPU) is the brain of the computer— the main chip responsible for doing the actual computing.

• The motherboard is the main circuit board within a computer.

• Read-only memory (ROM) chips store programs that con- trol the boot (startup) process and confi gure a computer’s components.

• Random-access memory (RAM) is volatile memory, which is lost when power is turned off. Programs are loaded into RAM because of its faster read speed.

• The hard disk drive (HDD) is typically the primary location of data storage within the computer.

• The computer’s operating system (OS) is the bridge between the human user and the computer’s electronic components. It provides the user with a working environment and facili- tates interaction with the system’s components.

• Formatting is the process of preparing a hard disk drive to store and retrieve data in its current form.

• A sector is the smallest unit of data that a hard drive can address. A cluster usually is the minimum space allocated to a fi le. Clusters are groups of sectors.

• A FAT is a fi le allocation table. It tracks the location of fi les and folders on the hard disk drive.

• Aspects of a computer that should be photographed close up at an electronic crime scene include (1) the screen of any run- ning computer monitor; (2) all the connections to the main sys- tem unit, such as peripheral devices (e.g., keyboard, monitor, speakers, mouse, etc.); and (3) equipment serial numbers.

• Evidentiary considerations may require the investigator to perform a live examination prior to disconnecting power.

• Two situations in which an investigator would not unplug a computer at an electronic crime scene are (1) if encryption is suspected, and thus pulling the plug would reencrypt the data, rendering it unreadable without a password or key, and (2) if data exists in RAM that has not been saved to the HDD and will thus be lost if power to the system is discontinued.

• The primary goal in obtaining data from an HDD is to do so with- out altering even one bit of data. To this end, a Message Digest 5 (MD5)/Secure Hash Algorithm (SHA) takes a “fi ngerprint” of a hard disk drive (HDD) before and after forensic imaging.

• The types of computer evidence can be grouped under two major subheadings: visible and latent data.

• Visible data is data that the operating system is aware of and thus is easily accessible to the user. It includes any type

of user-created data, such as word-processing documents, spreadsheets, accounting records, databases, and pictures.

• Temporary fi les created by programs as a sort of on-the- fl y backup can prove valuable as evidence. Data in the swap space used to conserve the valuable RAM within the computer system can also yield evidentiary data.

• Latent data is data that the operating system is not aware of. The constant shuffl ing of data through deletion, defrag- mentation, swapping, and so on, is one of the reasons data is stored in latent areas.

• Latent data can exist in both RAM slack and fi le slack. RAM slack is the area from the end of the logical fi le to the end of the sector. File slack is the remaining area from the end of the fi nal sector containing data to the end of the cluster.

• Latent data might be found in unallocated space—space on an HDD that the operating system sees as empty and ready for data.

• When a user deletes fi les, the data typically remains behind, so deleted fi les are another source of latent data.

• Places where a forensic computer examiner might look to de- termine what websites a computer user has visited recently are the Internet cache, cookies, and the Internet history.

• The history fi le can be located and read with a forensic soft- ware package. Another way to access websites that have been visited is by examining bookmarks and favorite places.

• IP addresses take the form ###.###.###.###, in which, gen- erally speaking, ### can be any number from 0 to 255.

• IP addresses provide the means by which data can be routed to the appropriate location, and they also provide the means by which most Internet investigations are conducted.

• An investigator tracking the origin of an e-mail seeks out the sender’s IP address in the e-mail’s header. Chat and in- stant messages are typically located in a computer’s random- access memory (RAM).

• Tracking the origin of unauthorized computer intrusions, or hacking, requires investigating a computer’s log fi le, RAM, and network traffi c.

• A fi rewall is a device designed to protect against intrusions into a computer network.

• Mobile devices offer many of the services that are offered by computers and other devices. These devices can provide a vast amount of useful and evidentiary data in an investigation.

• Leaving a mobile device running but placing it in something that will block its communication is the preferred method of choice for preserving data on a mobile device.

• Complications arise in extracting and evaluating data from mobile devices because of the variety of ways that different devices store and manage data.

COMPUTER FORENSICS

287

KEY TERMS

bit

bookmark

byte

central processing unit (CPU)

cluster

cookies

fi le slack

fi rewall

hacking

hard disk drive (HDD)

hardware

Internet cache

Internet history

latent data

Message Digest 5 (MD5)/Secure Hash Algorithm (SHA)

motherboard

operating system (OS)

partition

random-access memory (RAM)

sector

software

swap fi le

temporary fi les

unallocated space

visible data

COMPUTER FORENSICS

REVIEW QUESTIONS

1. Computer forensics involves the ______________ , ______________ , ______________ , ______________ , and ______________ of computer data.

2. True or False: Hardware comprises the physical components of the computer. ______________

3. ______________ is a set of instructions compiled into a program that performs a particular task.

4. (ROM, RAM) chips store programs used to start the boot process.

5. The term used to describe the chassis, including the moth- erboard and any other internal components of a personal computer, is ______________ .

6. True or False: The motherboard is a complex network of wires that carry data from one hardware device to another. ______________

7. True or False: The fi rst thing you should do when you encoun- ter a computer system in a forensic investigation is to connect the power supply and boot the system. ______________

8. RAM is referred to as volatile memory because it is not ______________ .

9. The brain of the computer is referred to as the ______________ .

10. The ______________ is the primary component of storage in a personal computer.

11. Personal computers typically communicate with each other through a(n) ______________ .

12. The computer’s ______________ permits the user to man- age fi les and applications.

13. A hard drive’s partitions are typically divided into ______________ , ______________ , ______________ , and ______________ .

14. A(n) ______________ is a single one or zero in the binary system and the smallest term in the language of computers.

15. A(n) ______________ is a group of eight bits.

16. A group of sectors, always units in multiples of two, is called a(n) ______________ .

17. An exact duplicate of the entire contents of a hard disk drive is known as a(n) ______________ .

18. All data readily available to a computer user is known as ______________ data.

19. A(n) ______________ fi le is created when data is moved from RAM to the hard disk drive to conserve space.

20. Most programs automatically save a copy of a fi le being worked on into a(n) ______________ fi le.

21. The existence of ______________ data is why a forensic image of the media is created.

22. The smallest unit of addressable space on a hard disk drive is the ______________ .

23. The two types of slack space are ______________ slack and ______________ slack.

24. ______________ slack is the area from the end of the data portion of the fi le to the end of the sector.

25. The portion of a disk that does not contain stored data is called ______________ .

26. True or False: Defragmenting a hard disk drive involves mov- ing noncontiguous data back together. ______________

27. True or False: A portion of a “deleted” fi le may be found in a computer’s unallocated space. ______________

28. A(n) ______________ takes the form of a series of numbers to route data to an appropriate location on the Internet.

29. A user’s hard disk drive will ______________ portions of webpages that have been visited.

30. A(n) ______________ is placed on a hard disk drive by a website to track certain information about its visitors.

31. E-mails have the ______________ address of the sender in the header portion of the mail.

32. True or False: Chat and instant messages conducted over the In- ternet are typically stored in RAM storage. ______________

33. When investigating a hacking incident, investigators con- centrate their efforts on three locations: ______________ , ______________ , and ______________ .

288

APPLICATION AND CRITICAL THINKING

1. If a fi le system defi nes a cluster as six sectors, how many bits of information can be stored on each cluster? Explain your answer.

2. Criminalist Tom Parauda is investigating the scene of a crime involving a computer. After he arrives, he photographs the overall scene and takes close-up shots of all the connections to the single computer involved, as well as photos of the serial numbers of the computer and all peripheral devices. Tom then labels the cord to each peripheral device, then dis- connects them from the computer. After making sure that all data in RAM has been saved to the hard disk drive, he un- plugs the computer from the wall. What mistakes, if any, did Tom make?

3. You are investigating a case in which an accountant is ac- cused of keeping fraudulent books for a fi rm. Upon examining his computer, you notice that the suspect uses two different accounting programs that are capable of reading the same types of fi les. Given this information, where would you prob- ably begin to search for latent data on the computer and why?

4. You are examining two computers to determine the IP ad- dress from which several threatening e-mails were sent. The fi rst computer uses Microsoft Outlook as an e-mail client and the second uses a web-based e-mail client. Where would you probably look fi rst for the IP addresses in each of these computers?

COMPUTER FORENSICS

34. Devices that permit only requested traffi c to enter a com- puter system are known as ______________ .

35. A(n) ______________ is a device that can prevent a mobile phone from communicating with a service provider.

36. True or False: Extracting and analyzing data from mo- bile devices is complicated because manufacturers of these devices store and manage data in a variety of ways. ______________

ENDNOTES

1. A megabyte (MB) is approximately one million bytes; a gigabyte (GB) is approximately one billion bytes, or 1,000 megabytes.

2. Actually, the more appropriate term is probably paging as opposed to swapping . This is because entire programs are typically not swapped in and out of memory to the swap space; rather, pages of memory are placed there.

289

290

From Chapter 11 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

Drugs

PABLO ESCOBAR, DRUG LORD In 1989 Forbes magazine listed Pablo Escobar as the seventh richest man in the world. Escobar began his climb to wealth as a teenage car thief in the streets of Medellin, Colombia, and eventually moved into the cocaine-smuggling business. At the peak of his power in the mid-1980s, he was shipping as much as eleven tons of cocaine per fl ight in jetliners to the United States. Law enforcement offi cials estimate that the Medellin cartel controlled 80 percent of the

world’s cocaine market and was taking in about $25 billion annually.

Escobar ruthlessly ruled by the gun: murdering, assassinating, and kidnapping. He was responsible for killing three presidential candidates in Colombia, as well as for the storming of the Colombian Supreme Court, which resulted in the murder of half the justices. All the while, Escobar curried favor with the Colombian general pub- lic by cultivating a Robin Hood image and distributing money to the poor.

In 1991, hoping to avoid extra- dition to the United States, Escobar turned himself in to the Colombian government and agreed to be sent to prison. However, the prison com- pound where he was sent could easily be mistaken for a country club. There

he continued his high-fl ying lifestyle, traffi cking by telephone and even murdering a few associates. When the Colombian government attempted to move Escobar to another jail, again fearing extradi- tion to the United States, he escaped.

Pressured by the US government, Colombia organized a task force dedicated to apprehend- ing Escobar. The manhunt for Escobar ended on December  2, 1993, when he was cornered on the roof of one of his hideouts. A shootout ensued, and Escobar was fatally wounded by a bullet behind the ear.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Compare and contrast psychological and physical

dependence. • Name and classify the commonly abused drugs. • Describe the laboratory tests normally used in a routine drug

identifi cation analysis. • Describe and explain the process of chromatography. • Explain the difference between thin-layer chromatography

and gas chromatography. • Describe the utility of ultraviolet and infrared spectroscopy

for the identifi cation of organic compounds. • Describe the concept and utility of mass spectrometry for

identifi cation analysis. • Understand the proper collection and preservation of drug

evidence.

Jesus Abad-El Colomiaano/AFP/Getty Images Jesus Abad El Colomiaano/AFP/Getty Iy magges

Drugs

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A drug can be defi ned as a natural or synthetic substance that is used to produce physiologi- cal or psychological effects in humans or other

animals. However, criminalists are concerned pri- marily with a small number of drugs—many of them illicit—that are commonly used for their intoxicating effects. These include marijuana, the most widely used illicit drug in the United States, and alcohol, which is consumed regularly by 90 million Americans. Drug abuse has grown from a problem generally as- sociated with members of the lower end of the so- cioeconomic ladder to one that cuts across all social and ethnic classes of society. Today, approximately 23 million people in the United States use illicit drugs.

Because of the epidemic proportions of ille- gal drug use, more than 75 percent of the evidence evaluated by crime laboratories in the United States is drug related (see Figure 1 ). The deluge of drug specimens has necessitated the expansion of existing crime laboratories and the creation of new ones. For many concerned forensic scientists, the crime labo- ratory’s preoccupation with drug evidence repre- sents a serious distraction that takes time away from evaluating evidence related to homicides and other types of serious crimes. However, the increasing caseloads associated with drug evidence have jus- tifi ed the expansion of forensic laboratory services. This expansion has increased the overall analytical capabilities of crime laboratories.

Drug Dependence In assessing the potential danger of drugs, society has become particularly conscious of their effects on human behavior. In fact, the fi rst drugs to be reg- ulated by law in the early years of the twentieth century were those deemed to have “habit-forming” properties. The early laws were aimed primarily at con- trolling opium and its derivatives; cocaine; and, later, marijuana. The ability of a drug to induce dependence after repeated use is submerged in a complex array of physiological and social factors.

Dependence on different drugs exists in numerous patterns and in all degrees of intensity, and depends on the nature of the drug, the route of administration, the dose, the frequency of administration, and the individual’s rate of metabolism. Furthermore, nondrug factors play an equally crucial role in determining the behavioral patterns associated with drug use. The personal characteristics of the user, his or her expectations about the drug experience, society’s attitudes toward and possible responses to the drug, and the setting in which the drug is used are all major determinants of drug dependence.

The questions of how to defi ne and measure a given drug’s infl uence on the individual and its danger to society are diffi cult to assess. The nature and signifi cance of drug dependence must be considered from two overlapping points of view: the interaction of the drug with the individual, and the drug’s impact on society. It will be useful to approach the problem from two dis- tinctly different aspects of human behavior: psychological dependence and physical dependence .

psychological dependence The conditioned use of a drug caused by underlying emotional needs.

physical dependence The physiological need for a drug brought about by its regular use and characterized by withdrawal sickness when administration of the drug is abruptly stopped.

FIGURE 1 A drug bust. Syracuse Newspapers/The Image Works

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PSYCHOLOGICAL

DEPENDENCE

The common denominator that characterizes all types of repeated drug use is psychological depen- dence on continued use of the drug. It is important to discard the unrealistic image that all drug users are hopeless “addicts” who are social dropouts. Most users present a quite normal appearance and remain both socially and economically integrated into the life of the community.

The reasons some people abstain from drugs while others become moderately or heavily in- volved are diffi cult if not impossible to delineate. Psychological needs arise from numerous personal and social factors that inevitably stem from the in- dividual’s desire to create a sense of well-being and to escape from reality. In some cases, the individual may seek relief from personal problems or stress- ful situations or may be trying to sustain a physical and emotional state that permits an improved level of performance. Whatever the reasons, the under- lying psychological needs and the desire to fulfi ll them create a conditioned pattern of drug abuse (see Figure 2 ).

The intensity of the psychological dependence associated with a drug’s use is diffi cult to defi ne and largely depends on the nature of the drug. For drugs such as alcohol, heroin, amphetamines, barbiturates, and cocaine, continued use will probably result in a high degree of involvement. Other drugs, such as marijuana and codeine, appear to have a considerably lower potential for the development of psychological dependence. However, this does not imply that repeated abuse of drugs deemed to have a low potential for psychologi- cal dependence is safe or will always produce low psychological dependence. We have no precise way to measure or predict the impact of drug abuse on the individual. Even if a system could be devised for controlling the many pos- sible variables affecting a user’s response, the unpredictability of the human personality would still come into play.

Our general knowledge of alcohol consumption should warn us of the fal- lacy of generalizing when attempting to describe the danger of drug abuse. Obviously, not all alcohol drinkers are psychologically addicted to the drug; most are “social” drinkers who drink in reasonable amounts and on an ir- regular basis. Many people have progressed beyond this stage and consider alcohol a necessary crutch for dealing with life’s stresses and anxieties. How- ever, a wide range of behavioral patterns exists among alcohol abusers, and to a large extent, the determination of the degree of psychological dependence must be made on an individual basis. Likewise, it would be fallacious to gener- alize that all users of marijuana can develop only a low degree of dependence on the drug. A wide range of factors also infl uences marijuana’s effect, and heavy users of the drug expose themselves to the danger of developing a high degree of psychological dependence.

PHYSICAL DEPENDENCE

Although emotional well-being is the primary motive leading to repeated and intensive use of a drug, certain drugs, taken in suffi cient dose and frequency, can produce physiological changes that encourage their continued use. Once

FIGURE 2 Young people drink- ing. Daytona Beach New- Journal/Jim Tiller\AP Wide World Photos

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the user abstains from such a drug, severe physical illness follows. The desire to avoid this withdrawal sickness , or abstinence syndrome , ultimately causes physical dependence, or addiction. Hence, for the addict who is accustomed to receiving large doses of heroin, the prospect of abstaining and encounter- ing the resulting body chills, vomiting, stomach cramps, convulsions, insom- nia, pain, and hallucinations is a powerful inducement for continuing to use.

Interestingly, some of the more widely abused drugs have little or no potential for creating physical dependence. Drugs such as marijuana, LSD, and cocaine create strong anxieties when their repeated use is discontinued; how- ever, no medical evidence attributes these discomforts to physiological reac- tions that accompany withdrawal sickness. On the other hand, use of alcohol, heroin, and barbiturates can result in the development of physical dependence.

Physical dependence develops only when the drug user adheres to a regular schedule of drug intake; that is, the interval between doses must be short enough so that the effects of the drug never wear off completely. For example, the interval between injections of heroin for the drug addict probably does not exceed six to eight hours. Beyond this time the addict will begin to experience the uncomfortable symptoms of withdrawal. Many users of heroin avoid taking the drug on a regular basis for fear of becoming physically addicted to its use. Similarly, the risk of developing physical dependence on alcohol becomes greatest when the consumption is characterized by a continuing pattern of daily use in large quantities.

Table 1 categorizes some of the more commonly abused drugs according to their effects on the body and summarizes their tendency to produce psy- chological dependence and to induce physical dependence with repeated use.

SOCIETAL ASPECTS OF DRUG USE

The social impact of drug dependence is directly related to the extent to which the user has become preoccupied with the drug. Here, the most important element is the extent to which drug use has become interwoven in the fabric of the user’s life. The more frequently the drug satisfi es the person’s need, the greater the likelihood that he or she will become preoccupied with its use, with a consequent neglect of individual and social responsibilities. Personal health, economic relationships, and family obligations may all suffer as the drug-seeking behavior increases in frequency and intensity and dominates the individual’s life. The extreme of drug dependence may lead to behavior that has serious implications for the public’s safety, health, and welfare.

Drug dependence in its broadest sense involves much of the world’s popula- tion. As a result, a complex array of individual, social, cultural, legal, and medi- cal factors ultimately infl uence society’s decision to prohibit or impose strict controls on a drug’s distribution and use. Invariably, society must weigh the benefi cial aspects of the drug against the ultimate harm its abuse will do to the individual and to society as a whole. Obviously, many forms of drug dependence do not carry suffi cient adverse social consequences to warrant their prohibi- tion, as illustrated by the widespread use of such drug-containing substances as tobacco and coffee. Although the heavy and prolonged use of these drugs may eventually damage body organs and injure an individual’s health, there is no evi- dence that they result in antisocial behavior, even with prolonged or excessive use. Hence, society is willing to accept the widespread use of these substances.

We are certainly all aware of the disastrous failure of the United States’ prohibition of alcohol use during the 1920s and also of the current debate on whether marijuana should be legalized. Each of these issues emphasizes the delicate balance between individual desires and needs and society’s concern with the consequences of drug abuse; moreover, this balance is continuously subject to change and reevaluation.

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Quick Review • A drug is a natural or synthetic substance that is used to produce physi-

ological or psychological effects in humans or other animals. • Nondrug factors that play a part in drug dependence include the personal

characteristics of the user, his or her expectations about the drug experi- ence, society’s attitudes toward and possible responses to the drug, and the setting in which the drug is used.

• Physical dependence is defi ned as a physiological need for a drug that has been brought about by its regular use. Psychological dependence is the conditioned use of a drug caused by underlying emotional needs.

TABLE 1 The Potential of Some Commonly Abused Drugs to Produce Dependence with Regular Use

DRUG PSYCHOLOGICAL

DEPENDENCE PHYSICAL

DEPENDENCE

Narcotics    

Morphine High Yes

Heroin High Yes

Methadone High Yes

Codeine Low Yes

Depressants    

Barbiturates (short-acting) High Yes

Barbiturates (long-acting) Low Yes

Alcohol High Yes

Methaqualone (Quaalude) High Yes

Meprobamate (Miltown, Equanil)

Moderate Yes

Diazepam (Valium) Moderate Yes

Chlordiazepoxide (Librium) Moderate Yes

Stimulants    

Amphetamines High ?

Cocaine High No

Caffeine Low No

Nicotine High Yes

Hallucinogens    

Marijuana Low No

LSD Low No

Phencyclidine (PCP) High No

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Types of Drugs

NARCOTIC DRUGS

The term narcotic is derived from the Greek word narkotikos , meaning “numb- ness” or “deadening.” Although pharmacologists classify narcotic drugs as substances that relieve pain and produce sleep, the term narcotic has become popularly associated with any drug that is socially unacceptable. As a conse- quence of this incorrect perception, many drugs are improperly called narcotics.

This confusion has produced legal defi nitions that differ from the phar- macological actions of many drugs. For example, until the early 1970s, most drug laws in the United States incorrectly designated marijuana as a narcotic. Even today, federal law classifi es cocaine as a narcotic drug; however, phar- macologically speaking, cocaine is actually a powerful central nervous system stimulant, possessing properties opposite those normally associated with the depressant effects of a narcotic.

OPIATES Medical professionals apply the term opiate to most of the drugs properly classifi ed as narcotics. Opiates behave pharmacologically like mor- phine, which is a painkiller derived from opium —the gummy, milky juice that exudes from cuts made on the unripe pods of the Asian poppy (Papaver somniferium) . Although morphine is readily extracted from opium, the most commonly used opium-based drug is heroin, which is produced by reacting morphine with acetic anhydride or acetyl chloride (see Figure 3 ). Heroin’s high solubility in water makes its street preparation for intravenous admin- istration rather simple, and only by injection are heroin’s effects felt almost instantaneously and with maximum sensitivity. To prepare the drug for injec- tion, the addict frequently dissolves it in a small quantity of water in a spoon. The process can be speeded up by heating the spoon over a candle or several matches. The solution is then drawn into a syringe or eyedropper and injected under the skin (see Figure 4 ).

narcotic A drug that induces sleep and depresses vital body functions such as blood pressure, pulse rate, and breathing rate.

FIGURE 3 The opium poppy and its derivatives. Shown are the poppy plant, crude and smoking opium, codeine, heroin, and morphine. Pearson Education/PH College

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Heroin and other narcotic drugs are analgesics —that is, they relieve pain by depressing the central nervous system. Besides being a powerful analgesic, heroin produces a “high” that is accompanied by drowsiness and a deep sense of well-being. The effect is short, generally lasting only three to four hours. Regular use of heroin—or any other narcotic drug—invariably leads to physi- cal dependence, with all its dire consequences.

Codeine is also present in opium, but it is usually prepared synthetically from morphine. It is commonly used as a cough suppressant in prescription cough syrup. Codeine, only one-sixth as strong as morphine, is not an attrac- tive street drug for addicts.

SYNTHETIC OPIATES A number of narcotic drugs are not naturally derived from opium. However, because they have similar physiological effects on the body as the opium narcotics, they are also commonly referred to as opiates.

Methadone is perhaps the best known synthetic opiate. In the 1960s, scientists discovered that a person who received periodic doses of methadone would not get high if he or she then took heroin or morphine. Although meth- adone is pharmacologically related to heroin, its administration appears to eliminate the addict’s desire for heroin, with minimal side effects. These dis- coveries led to the establishment of controversial methadone maintenance programs in which heroin addicts receive methadone to reduce or prevent future heroin use. Physicians increasingly prescribe methadone for pain relief. Unfortunately, the wide availability of methadone for legitimate medical pur- poses has recently led to greater quantities of the drug being diverted into the illicit market.

In 1995, the US Food and Drug Administration (FDA) approved the drug OxyContin for use as a painkiller. The active ingredient in OxyContin is oxyco- done, a synthetic drug closely related to morphine and heroin in its chemical structure. OxyContin is an analgesic narcotic that has effects similar to those of heroin. It is prescribed for treatment of chronic pain, with doctors writing millions of OxyContin prescriptions each year. The drug has a time-release formula that the manufacturer initially believed would reduce the risk of abuse and addiction. This has not turned out to be the case. It is estimated that close to a quarter of a million individuals abuse the drug.

FIGURE 4 Heroin paraphernalia. Drug Enforcement Administration

analgesic A substance that lessens or eliminates pain.

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DRUGS

Because it is a legal drug that is diverted from legitimate sources, OxyContin is obtained very differently from illegal drugs. Pharmacy robberies, forged prescriptions, and theft of the drug from patients with a legitimate prescription are ways abusers access OxyContin. Some abusers visit numerous doctors and receive prescriptions even though their medical condition may not warrant it.

HALLUCINOGENS

Hallucinogens are drugs that can cause marked alterations in normal thought processes, perceptions, and moods. Perhaps the most popular and controver- sial member of this class of drugs is marijuana.

MARIJUANA Marijuana is the popular name of the plant Cannabis sativa , a weed that will grow wild in most climates. The Cannabis plant contains a chemi- cal known as tetrahydrocannabinol , or THC, which produces the psychoactive effects experienced by users. The THC content of Cannabis varies in differ- ent parts of the plant. The greatest concentration is usually found in a sticky resin produced by the plant, known as hashish . Declining concentrations are typically found in the fl owers and leaves, respectively. Little THC is found in the stem, roots, or seeds of the plant. The potency and resulting effect of the drug fl uctuate, depending on the relative proportion of these plant parts in the marijuana mixture consumed by the user. The most common method of administration is by smoking either the dried fl owers and leaves or various preparations of hashish (see Figure 5 ). Marijuana is also occasionally taken orally, typically baked in sweets such as brownies or cookies.

Any study of marijuana’s effect on humans must consider the potency of the marijuana preparation. An interesting insight into the relationship between dosage level and marijuana’s pharmacological effect was presented in the fi rst report of the National Commission on Marijuana and Drug Abuse:

At low, usual “social” doses the user may experience an increased sense of well- being; initial restlessness and hilarity followed by a dreamy, carefree state of relax- ation; alteration of sensory perceptions including expansion of space and time; a more vivid sense of touch, sight, smell, taste and sound; a feeling of hunger, espe- cially a craving for sweets; and subtle changes in thought formation and expres- sion. To an unknowing observer, an individual in this state of consciousness would not appear noticeably different from his normal state.

At higher, moderate doses these same reactions are intensifi ed but the changes in the individual would still be scarcely noticeable to an observer. At very high doses, psychotomimetic phenomena may be experienced. These include distortion of body image, loss of personal identity, sensory and mental illusions, fantasies and hallucinations. 1

CLOSER ANALYSIS WHAT’S IN THAT BAG?

The contents of a typical bag of heroin is an excellent example of the uncertainty attached to buying illicit drugs. For many years in the 1960s and into the early 1970s, the average bag contained 15 to 20  percent heroin. Currently, the average purity of heroin obtained in the illicit US market is approximately 35 percent. The addict rarely knows or cares what composes the other 65 percent or so of the

material. Traditionally, quinine has been the most common diluent of heroin. Like heroin, it has a bitter taste and was probably origi- nally used to obscure the actual potency of a heroin preparation from those who wished to taste-test the material before buying it. Other diluents commonly added to heroin are starch, lactose, procaine (Novocain), and mannitol.

hallucinogen A substance that induces changes in normal thought processes, perceptions, and moods.

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DRUGS

Marijuana easily qualifi es as the most widely used illicit drug in the United States. For instance, more than 43 million Americans have tried marijuana, according to the latest surveys, and almost half that number may be regular users. In addition to its widespread illegal use, accumulating evidence suggests that marijuana has potential medical uses. Two promising areas of research are marijuana’s reduction of excessive eye pressure in sufferers of glaucoma and the lessening of nausea caused by powerful anticancer drugs. Marijuana may also be useful as a muscle relaxant.

No current evidence suggests that experimental or intermittent use of marijuana causes physical or psychological harm. Marijuana does not cause physical dependence. However, the risk of harm lies instead in heavy, long-term use, particularly of the more potent preparations. Heavy users can develop a strong psychological dependence on the drug. Some effects of marijuana use include increased heart rate, dry mouth, reddened eyes, impaired motor skills and concentration, and frequently hunger and an increased desire for sweets.

OTHER HALLUCINOGENS A substantial number of other substances with widely varying chemical compositions are also used recreationally because of their hallucinogenic properties. These include both naturally occurring substances such as mescaline and psilocybin and synthetically created drugs including lysergic acid diethylamide (LSD) and phencyclidine (PCP).

LSD is synthesized from lysergic acid, a substance derived from ergot, which is a type of fungus that attacks certain grasses and grains. The drug appears in a variety of forms—as a pill, added to a cube of sugar, or absorbed onto a small piece of paper—and is taken orally. Its hallucinogenic effects were fi rst described by the Swiss chemist Albert Hofmann after he accidentally ingested some of the material in his laboratory in 1943. LSD produces marked changes in mood, leading to laughing or crying at the slightest provocation. Feelings of anxiety and tension almost always accompany LSD use. LSD is very potent; as little as 25 micrograms is enough to induce vivid visual hallu- cinations that can last for about twelve hours. Although physical dependence

FIGURE 5 Several rolled marijuana cigarettes lie on a pile of crushed, dried marijuana leaves next to a tobacco cigarette. Photo courtesy US Department of Justice, Drug Enforcement Administration

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does not develop with continued use, the individual user may be prone to fl ashbacks and psychotic reactions even after use is discontinued.

Abuse of the hallucinogen phencyclidine, commonly called PCP, has recently grown to alarming proportions. Because this drug can be synthesized by simple chemical processes, it is manufactured surreptitiously for the illicit market in so-called clandestine laboratories (see Figure 6 ). These laboratories range from large, sophisticated operations to small labs located in garages or bathrooms. Small-time operators normally have little or no training in chemis- try and employ “cookbook” methods to synthesize the drug. Some of the more knowledgeable and experienced operators have been able to achieve clandes- tine production levels that approach a commercial level of operation.

CLOSER ANALYSIS MARIJUANA AND HASHISH

Marijuana is a weed that will grow wild in most climates. The plant grows to a height of 5 to 15 feet and is characterized by an odd num- ber of leafl ets on each leaf. Normally each leaf contains fi ve to nine leafl ets, all with serrated or sawtooth edges.

The potency of marijuana depends on its form. Marijuana in the form of loose vegetation has an average THC content of about 3  to  4.5 percent. The more potent sinsemilla form averages about 6  to 12  percent in THC content. Sinsemilla is the unfertilized fl ow- ering tops of the female Cannabis plants, acquired by removing all male plants from the growing fi eld at the fi rst sign of their appear- ance. Production of sinsemilla requires a great deal of attention and care, and the plant is therefore cultivated on small plots.

Hashish preparations average about 2 to 8 percent THC. On the illicit drug market, hashish (see photo) usually appears in the form

of compressed vegetation containing a high percentage of resin. A particularly potent form of hashish is known as liquid hashish or hashish oil . Hashish in this form is normally a viscous substance, dark green with a tarry consistency. Liquid hashish is produced by effi ciently extracting the THC-rich resin from the marijuana plant with an appropriate solvent, such as alcohol. The THC content of liquid hashish typically varies from 8 to 22 percent. Because of its extraor- dinary potency, one drop of the material can produce a “high.”

Blocks of hashish in front of leaves and fl owering tops of the marijuana plant. Courtesy James King-Holmes, Photo Researchers, Inc.

The marijuana leaf. Courtesy Drug Enforcement Administration, Washington, DC

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DRUGS

Phencyclidine is often mixed with other drugs, such as LSD or amphet- amines, and is sold as a powder (known as “angel dust”), capsule, or tablet, or as a liquid sprayed on plant leaves. The drug is smoked, ingested, or sniffed. Following oral intake of moderate doses (1 to 6 milligrams), the user fi rst experiences feelings of strength and invulnerability, along with a dreamy sense of detachment. However, the user soon becomes unresponsive, confused, and agitated. Depression, irritability, feelings of isolation, audio and visual hallu- cinations, and sometimes paranoia accompany PCP use. Severe depression, tendencies toward violence, and suicide accompany long-term daily use of the drug. In some cases, the PCP user experiences sudden schizophrenic behavior days after the drug has been taken.

DEPRESSANTS

Depressants are drugs that slow down, or depress, the central nervous sys- tem. Several types of drugs fall into this category, including the most widely used drug in the United States: alcohol.

CLOSER ANALYSIS SYNTHETIC CANNABIS

A drug that contains synthetic cannabinoids has taken on the street names of K2 and Spice. Spice is typically sprayed onto incense and is usually smoked by users. When synthetic cannabis fi rst went on sale in 2004, it was thought to mimic the effect of cannabis through a mixture of legal herbs. However, laboratory analysis later proved that spice in fact contains synthetic cannabiniods that act on the body in a similar way to the cannabiniods found in marijuana, such

as THC. Although its effects are not well documented, extremely large doses of spice may cause negative effects that exceed those from marijuana use, such as increased agitation and vomiting. In 2011, the US Drug Enforcement Agency categorized the synthetic cannabinoids typically found in spice as controlled substances. Spice does not cause a positive drug test for cannabis or other illegal drugs.

FIGURE 6 A scene from a clandestine drug laboratory. Drug Enforcement Administration

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ALCOHOL (ETHYL ALCOHOL) Many people overlook the fact that alcohol is a drug; however, it exerts a powerful depressant action on the central nervous system. When alcohol enters the bloodstream, it quickly travels to the brain, where it suppresses the brain’s control of thought processes and muscle coordination. Low doses of alcohol tend to inhibit the mental processes of judgment, memory, and concentration. The drinker’s personality becomes expansive, and he or she exudes confi dence. When taken in moderate doses, alcohol reduces coordination substantially, inhibits orderly thought processes and speech patterns, and slows reaction times. Under these conditions, the ability to walk or drive becomes noticeably impaired. Higher doses of alcohol may cause the user to become highly irritable and emotional; displays of anger and crying are not uncommon. Extremely high doses may cause an individual to lapse into unconsciousness or even a comatose state that can precede a fatal depression of circulatory and respiratory functions. The behavioral patterns of alcohol intoxication vary and depend partly on such factors as the social setting, the amount consumed, and the personal expectation of the individual with regard to alcohol.

In the United States, the alcohol industry annually produces more than one billion gallons of spirits, wine, and beer for which 90 million consumers pay nearly $40 billion. Unquestionably, these and other statistics support the fact that alcohol is the most widely used and abused drug (see Figure 7 ).

BARBITURATES Barbiturates are derivatives of barbituric acid, a substance fi rst synthesized by a German chemist, Adolf Von Bayer, more than a hundred years ago. They are commonly referred to as “downers” because they relax the user, create a feeling of well-being, and produce sleep. Like alcohol, barbiturates suppress the vital functions of the central nervous system. Twenty-fi ve barbi- turate derivatives are currently used in medical practice in the United States; however, only fi ve—amobarbital, secobarbital, phenobarbital, pentobarbital, and butabarbital—are used for most medical applications.

Normally, barbiturate users take these drugs orally. The average sedative dose is about 10 to 70 milligrams. When taken in this fashion, the drug enters the blood through the walls of the small intestine. Some barbiturates, such as

depressant A substance that slows down, or depresses, the functions of the central nervous system.

FIGURE 7 Rows of bottles of alcohol behind a bar. Jeremy Liebman/Stone/Getty Images

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phenobarbital, are classifi ed as long-acting barbiturates. They are absorbed into the bloodstream more slowly than others and therefore produce less pronounced effects than faster-acting barbiturates. The slow action of phenobarbital accounts for its low incidence of abuse. Apparently, barbiturate abusers prefer the faster-acting varieties: secobarbital, pentobarbital, and amobarbital.

In the early 1970s, a nonbarbiturate depressant, methaqualone (brand name Quaalude), appeared on the illicit-drug scene. Methaqualone is a pow- erful sedative and muscle relaxant that possesses many of the depressant properties of barbiturates. When taken in prescribed amounts, barbiturates are relatively safe, but in instances of extensive and prolonged use, physical dependence can develop.

ANTIPSYCHOTIC AND ANTIANXIETY DRUGS Although antipsychotic and antianxiety drugs can be considered depressants, they differ from barbitu- rates in the extent of their effects on the central nervous system. Generally, these drugs produce a relaxing tranquility without impairing high-thinking faculties or inducing sleep. Antipsychotics, such as reserpine and chlorproma- zine, have been used to reduce the anxieties and tension of mental patients. A group of antianxiety drugs are commonly prescribed to deal with the everyday tensions of many healthy people. These drugs include meprobamate (Miltown), chlordiazepoxide (Librium), diazepam (Valium), and Xanax.

In the past forty-fi ve years, the use of these drugs—particularly antianxi- ety drugs—has grown dramatically. Medical evidence shows that these drugs produce psychological and physical dependence with repeated and high levels of usage. For this reason, the widespread prescribing of antianxiety drugs to overcome the pressures and tensions of life has worried many people who fear a legalized drug culture is being created.

“HUFFING” Since the early 1960s, “huffi ng,” the practice of sniffi ng materi- als containing volatile solvents (airplane glue or model cement, for example), has grown in popularity. Another dimension has more recently been added to the problem with the increasing popularity of sniffi ng aerosol gas propel- lants such as freon. All materials abused by huffi ng contain volatile or gaseous substances that are primarily central nervous system depressants. Although toluene (a solvent used in airplane glue) seems to be the most popular solvent to sniff, others can produce comparable physiological effects. These chemicals include naphtha, methyl ethyl ketone (i.e., antifreeze), gasoline, and trichloro- ethylene (a dry-cleaning solvent).

The usual immediate effects of huffi ng are a feeling of exhilaration and eu- phoria combined with slurred speech, impaired judgment, and double vision. Finally, the user may experience drowsiness and stupor, with these depres- sant effects slowly wearing off as the user returns to a normal state. Although most experts believe that users become psychologically dependent on the effects achieved by huffi ng, little evidence suggests that solvent inhalation is addictive. However, huffers expose themselves to the danger of liver, heart, and brain damage from the chemicals they have inhaled. Even worse, sniffi ng of some solvents, particularly halogenated hydrocarbons such as freon and related gases, is accompanied by a signifi cant risk of immediate death.

STIMULANTS

The term stimulants refers to a range of drugs that stimulate, or speed up, the central nervous system.

AMPHETAMINES Amphetamines are a group of synthetic stimulants that share a similar chemical structure and are commonly referred to in the terminology of

stimulant A substance that speeds up, or stimulates, the activity of the central nervous system.

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the drug culture as “uppers” or “speed.” They are typically taken either orally or via intravenous injection and provide a feeling of well-being and increased alertness that is followed by a decrease in fatigue and a loss of appetite. However, these apparent ben- efi ts of the drug are accompanied by restlessness and instability or apprehensiveness, and once the stimulant effect wears off, depression may set in.

In the United States, the most serious form of amphetamine abuse stems from intravenous injection of amphetamine or its chemical derivative, methamphetamine (see Figure 8 ). The de- sire for a more intense amphetamine experience is the primary motive for this route of administration. The initial sensation of a “fl ash” or “rush,” followed by an intense feeling of pleasure, constitutes the principal appeal of the intravenous route for the user. During a “speed binge,” the individual may inject amphet- amines every two to three hours. Users have reported experi- encing a euphoria that produces hyperactivity, with a feeling of clarity of vision as well as hallucinations. As the effect of the amphetamines wears off, the individual lapses into a period of exhaustion and may sleep continuously for one or two days. Following this, the user often experiences a prolonged period of severe depression lasting from days to weeks.

A smokable form of methamphetamine, known as “ice,” is reportedly in heavy demand in some areas of the United States. Ice is prepared by slowly evaporating a methamphetamine solution to produce large, crystal-clear “rocks.” Like crack cocaine (discussed next), ice is smoked and produces effects similar to those of crack cocaine, but the effects last longer. Once the effects of ice wear off, users often become depressed and may sleep for days. Chronic users exhibit violent destructive behavior and acute psychosis similar to paranoid schizophrenia. Repeated use of amphetamines leads to a strong psychological dependence, which encour- ages their continued use.

COCAINE Between 1884 and 1887, pioneering psychologist Sigmund Freud created something of a sensation in European medical circles by describing his experiments with a new drug. He reported a substance of seemingly limitless potential as a source of “exhilaration and lasting euphoria” that permitted “intensive mental or physical work [to be] performed without fatigue.” He wrote, “It is as though the need for food and sleep was completely banished.”

The object of Freud’s enthusiasm was cocaine, a stimulant extracted from the leaves of Erythroxylon coca , a plant grown in the Andes mountains of South America as well as in tropi- cal Asia (see Figure 9 ). Most commonly, cocaine is sniffed or “snorted” and absorbed into the body through the mucous membranes of the nose, but it is sometimes injected. Cocaine is a powerful stimulant to the central nervous system, and its effects resemble those caused by amphetamines—namely, increased alertness and vigor accompanied by suppression of hunger, fatigue, and boredom. Cocaine produces a feeling of euphoria by stimulating a pleasure center in the base of the brain, in an area connected to nerves that are responsible for emotions. It stimulates this pleasure center to a far greater degree than it would ever normally be stimulated. Some regular users of cocaine report accompanying feelings of restlessness,

FIGURE 8 Granular amphetamine beside a razor blade. Cordelia Molloy\Photo Researchers, Inc.

FIGURE 9 Coca leaves and illicit forms of cocaine. Drug Enforcement Administration

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DRUGS

irritability, and anxiety. Cocaine used chronically or at high doses can have toxic effects. Cocaine-related deaths result from cardiac arrest or seizures followed by respiratory arrest.

A particularly potent form of cocaine known as “crack” can be produced by mixing cocaine with baking soda and water and then heating the resulting solution. This material is then dried and broken into tiny chunks that dealers sell as crack “rocks” that are suffi ciently volatile to be smoked. The faster the cocaine level rises in the brain, the greater the euphoria, and the fastest way to attain a rise in the brain’s cocaine level is to smoke crack. Inhaling the cocaine vapor delivers the drug to the brain in less than fi fteen seconds—about as fast as injecting it and much faster than snorting it. The dark side of crack, how- ever, is that the euphoria fades quickly as the cocaine levels rapidly drop, leav- ing the user feeling depressed, anxious, and pleasureless. The desire to return to the euphoric feeling is so intense that crack users quickly develop a habit for the drug that is almost impossible to overcome. Only a small percentage of crack abusers are ever cured of this drug habit. When a person uses large amounts of crack cocaine numerous times, he or she usually develops a sense of paranoia. Paronoid delusions cause the person to lose his or her sense of reality, leaving him or her trapped in a world full of voices, whispers, and sus- picions. Sufferers come to believe that they are being followed and that their drug use is being watched.

In the United States, cocaine abuse is on the rise. Many people are using cocaine apparently to improve their ability to work and to keep going when tired. Although there is no evidence of physical dependency accompanying cocaine’s repeated use, abstention from cocaine after prolonged use brings on severe bouts of mental depression, which produce a very strong compulsion to resume using the drug. In fact, laboratory experiments with animals have demonstrated that, of all the commonly abused drugs, cocaine produces the strongest psychological compulsions for continued use.

The United States spends millions of dollars annually in attempting to control cultivation of the coca leaf in various South American countries and to prevent the traffi cking of cocaine into the United States. Three-quarters of the cocaine smuggled into the United States was refi ned in clandestine laboratories in Colombia. The profi ts are astronomical. Peruvian farmers may be paid $200 for enough coca leaves to make one pound of cocaine. The refi ned cocaine is worth $1,000 when it leaves Colombia and sells at retail in the United States for up to $20,000.

CLUB DRUGS

The term club drugs refers to synthetic drugs that are often used at nightclubs, bars, and raves (i.e., all-night dance parties). Substances that are used as club drugs include, but are not limited to, MDMA (or Ecstasy; see Figure 10 ), GHB (gamma hydroxybutyrate), Rohypnol (“roofi es”), ketamine, and methamphet- amine. These drugs have become popular on the dance scene as a way to induce the rave experience. A high incidence of use has been found among teens and young adults.

GHB and Rohypnol are central nervous system depressants that are often connected with drug-facilitated sexual assault, rape, and robbery. Effects accompanying the use of GHB include dizziness, sedation, headache, and nausea. Recreational users have reported euphoria, relaxation, disinhibition, and increased libido (i.e., sex drive). Rohypnol causes muscle relaxation, loss of consciousness, and an inability to remember what happened during the hours after ingesting the drug. Users of this drug are at particular risk of sexual assault because victims are physically unable to resist the attack. Effects are even stronger when the drug is combined with alcohol because the user

306

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experiences memory loss, blackouts, and disinhibition. Unsuspecting victims of intentional druggings become drowsy or dizzy. Drugs such as Rohypnol and GHB are odorless, colorless, and tasteless, and thus remain undetected when slipped into a drink.

Methylenedioxymethamphetamine, also known as MDMA or Ecstasy, is a synthetic, mind-altering drug that exhibits many hallucinogenic and amphetamine-like effects. Ecstasy was originally patented as an appetite suppressant and was later discovered to induce feelings of happiness and relaxation. Recreational drug users fi nd that Ecstasy enhances self-awareness and decreases inhibitions. However, seizures, muscle breakdown, stroke, kidney failure, and cardiovascular system failure often accompany chronic abuse of Ecstasy. In addition, chronic use of Ecstasy leads to serious dam- age to the areas of the brain responsible for thought and memory. Ecstasy increases heart rate and blood pressure; produces muscle tension, teeth grinding, and nausea; and causes psychological diffi culties such as confusion, severe anxiety, and paranoia. The drug can cause signifi cant increases in body temperature from the combination of the drug’s stimulant effect with the often hot, crowded atmosphere of a rave club.

Ketamine is primarily used in veterinary medicine as an animal anesthetic. When used by humans, the drug can cause euphoria and feelings of unreality accompanied by visual hallucinations. Ketamine can also cause impaired motor function, high blood pressure, amnesia, and mild respiratory depression.

ANABOLIC STEROIDS

Anabolic steroids are synthetic compounds that are chemically related to the male sex hormone testosterone. Testosterone has two effects on the body. It promotes the development of secondary male characteristics (i.e., andro- genic effects), and it accelerates muscle growth (i.e., anabolic effects). Efforts to promote muscle growth and to minimize the hormone’s androgenic effects have led to the synthesis of numerous anabolic steroids. However, a steroid

FIGURE 10 Ecstasy, a popular club drug. Courtesy Rusty Kennedy, AP Wide World Photos

anabolic steroids Synthetic compounds, chemically related to the male sex hormone testosterone, that are used to promote muscle growth.

307

DRUGS

free of the accompanying harmful side effects of an androgen drug has not yet been developed.

Incidence of steroid abuse fi rst received wide- spread public attention when both amateur and professional athletes were discovered using these sub- stances to enhance their performance. Interestingly, current research on male athletes given anabolic ste- roids has generally found little or, at best, marginal evidence of enhanced strength or performance. Although the full extent of anabolic steroid abuse by the general public is not fully known, the US govern- ment is suffi ciently concerned to regulate the avail- ability of these drugs to the general population and to severely punish individuals for illegal possession and distribution of anabolic steroids. In 1991, anabolic steroids were classifi ed as controlled dangerous sub- stances, and the Drug Enforcement Administration was given enforcement power to prevent their illegal use and distribution (see Figure 11 ).

Anabolic steroids are usually taken by individuals who are unfamiliar with their harmful medical side effects. Liver cancer and other liver malfunctions have been linked to steroid use. These drugs also cause masculinizing effects in females, infertility, and diminished sex drive in males. For teenagers, anabolic steroids result in the premature halting of bone growth. Anabolic steroids can also cause unpredictable effects on mood and personality, leading to unpro- voked acts of anger and destructive behavior. Depression is also a frequent side effect of anabolic steroid abuse.

Quick Review • Narcotic drugs are analgesics, meaning that they relieve pain by depressing

the central nervous system. • The most common source for narcotic drugs is opium. Morphine is

extracted from opium and used to synthesize heroin. • Opiates are not derived from opium or morphine, but they have the same

physiological effects on the body. Examples of opiates are methadone and OxyContin (i.e., oxycodone).

• Hallucinogens cause marked changes in normal thought processes, perceptions, and moods. Marijuana is the most well-known drug in this class. Other hallucinogens include LSD, mescaline, PCP, psilocybin, and MDMA (or Ecstasy).

• Depressants decrease the activity of the central nervous system, calm irritability and excitability, and produce sleep. Depressants include alcohol (i.e., ethanol), barbiturates, tranquilizers, and various substances that can be sniffed such as airplane glue and model cement.

• Stimulants increase the activity of the central nervous system and are taken to increase alertness and activity. Stimulants include amphetamines, sometimes known as “uppers” or “speed,” and cocaine, which in its free- base form is known as “crack.”

• Club drugs are synthetic drugs that are used at nightclubs, bars, and raves (i.e., all-night dance parties). Some club drugs act as stimulants; others have depressant effects.

• Anabolic steroids are synthetic compounds that are chemically related to the male sex hormone testosterone. Anabolic steroids are often abused by individuals who are interested in accelerating muscle growth.

FIGURE 11 Anabolic steroids: a vial of testosterone and a syringe. Testosterone, the male sex hormone, is sometimes abused by athletes for its protein-building (anabolic) effect. SPL\Photo Researchers Inc.

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DRUGS

Drug-Control Laws The provisions of drug laws are of particular interest to the criminalist, for they may impose specifi c analytical requirements on drug analysis. For example, the severity of a penalty associated with the manufacture, distribution, possession, and use of a drug may depend on the weight of the drug or its concentration in a mixture. In such cases, the chemist’s report must contain all information that is needed to properly charge a suspect under the provisions of the existing law.

The provisions of any drug-control law are an outgrowth of national and local law enforcement requirements and customs, as well as the result of moral and political philosophies. These factors have produced a wide spectrum of national and local drug-control laws. Although their detailed discussion is beyond the intended scope of this text, a brief description of the US federal law known as the Controlled Substances Act will illustrate a legal drug classi- fi cation system that has been created to prevent and control drug abuse. Many states have modeled their own drug-control laws after this act, an important step in establishing uniform drug-control laws throughout the United States.

Collection and Preservation of Drug Evidence Preparation of drug evidence for submission to the crime laboratory is normally relatively simple and accomplished with minimal precautions in the fi eld. The fi eld investigator must ensure that the evidence is properly packaged and labeled for delivery to the laboratory. Considering the countless forms and varieties of drug evidence that are seized, it is not practical to prescribe any single packag- ing procedure for fulfi lling these requirements. Generally, common sense is the best guide in such situations, keeping in mind that the package must prevent loss and/or cross-contamination of the contents. Often, the original container in which the drug was seized will meet these requirements. Specimens suspected of containing volatile solvents, such as those involved in glue-sniffi ng cases, must be packaged in an airtight container to prevent evaporation of the solvent. All packages must be marked with suffi cient information to ensure identifi cation by the offi cer in future legal proceedings and to establish the chain of custody.

To aid the drug analyst, the investigator should supply any background information that may relate to a drug’s identity. Analysis time can be mark- edly reduced when the chemist has this information. For the same reason, the results of drug-screening tests used in the fi eld must also be transmitted to the laboratory. However, although these tests may indicate the presence of a drug and may help the offi cer establish probable cause to search and arrest a suspect, they do not offer conclusive evidence of a drug’s identity.

Quick Review • Federal law establishes fi ve schedules of classifi cation for controlled

dangerous substances on the basis of a drug’s potential for abuse, potential for physical and psychological dependence, and medical value.

• The packaging of drug evidence must prevent loss and/or cross- contamination of the contents, and often the original container in which the drug was seized is used. Specimens suspected of containing volatile solvents must be packaged in an airtight container to prevent evaporation.

• The investigator may help in the identifi cation of the drug by supplying to the drug analyst any background information that may relate to the drug’s identity.

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DRUGS

CLOSER ANALYSIS CONTROLLED SUBSTANCES ACT

The federal Controlled Substances Act establishes fi ve schedules of classifi cation for controlled dangerous substances on the basis of a drug’s potential for abuse, potential for physical and psychological dependence, and medical value. This classifi cation system is extremely fl exible in that the US attorney general has the authority to add, delete, or reschedule a drug as more information becomes available.

Schedule I. Schedule I drugs have a high potential for abuse, have no currently accepted medical use in the United States, and/or lack accepted safety for use in treatment under medical supervision. Drugs controlled under this schedule include heroin, marijuana, methaqualone, and LSD.

Schedule II. Schedule II drugs have a high potential for abuse, a currently accepted medical use or a medical use with severe restrictions, and a potential for severe psychological or physical dependence. Schedule II drugs include opium and its derivatives not listed in schedule I, cocaine, methadone, phencyclidine (PCP), most amphetamine preparations, and most barbiturate prepara- tions containing amobarbital, secobarbital, and pentobarbital. Dronabinol, the synthetic equivalent of the active ingredient in marijuana, has been placed in schedule II in recognition of its growing medical uses in treating glaucoma and chemotherapy patients.

Schedule III. Schedule III drugs have less potential for abuse than those in schedules I and II, a currently accepted medical use in the United States, and a potential for low or moderate physical dependence or high psychological dependence. Schedule III controls, among other substances, all barbiturate preparations (except phenobarbi- tal) not covered under schedule II and certain codeine preparations. Anabolic steroids were added to this schedule in 1991.

Schedule IV. Schedule IV drugs have a low potential for abuse relative to schedule III drugs and have a current medical use in the United States; their abuse may lead to limited dependence relative to schedule III drugs. Drugs controlled in this schedule include propoxyphene (Darvon), phenobarbital, and tranquil- izers such as meprobamate (Miltown), diazepam (Valium), and chlordiazepoxide (Librium).

Schedule V. Schedule V drugs must show low abuse potential, have medical use in the United States, and have less potential for pro- ducing dependence than schedule IV drugs. Schedule V controls certain opiate drug mixtures that contain nonnarcotic medicinal ingredients.

Controlled dangerous substances listed in schedules I and II are subject to manufacturing quotas set by the attorney general. For example, eight billion doses of amphetamines were manufactured in

CONTROL MECHANISMS OF THE CONTROLLED SUBSTANCES ACT

Schedule Registration Record Keeping

Manufacturing Quotas

Distribution Restrictions

Dispensing Limits

I Required Separate Yes Order forms Research use only II Required Separate Yes Order forms Rx: written; no refi lls III Required Readily retrievable s No, but some drugs

limited by schedule II quotas

Records required Rx: written or oral; with medical authorization refi lls up to 5 times in 6 months

IV Required Readily retrievable No, but some drugs limited by schedule II quotas

Records required Rx: written or oral; with medical authorization refi lls up to 5 times in 6 months

V Required Readily retrievable No, but some drugs limited by schedule II quotas

Records required Over-the-counter (Rx drugs limited to MD’s order) refi lls up to 5 times

Forensic Drug Analysis One only has to look into the evidence vaults of crime laboratories to appreciate the assortment of drug specimens that confront the criminalist. The presence of a huge array of powders, tablets, capsules, vegetable matter, liquids, pipes, cigarettes, cookers, and syringes is testimony to the vitality and sophistication of the illicit-drug market. If outward appearance is not evidence enough of

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the United States in 1971. In 1972, production quotas were estab- lished reducing amphetamine production approximately 80 percent below 1971 levels.

The criminal penalties for the unauthorized manufacture, sale, or possession of controlled dangerous substances are related to the schedules as well. The most severe penalties are associated with drugs listed in schedules I and II. For example, for drugs included in schedules I and II, a fi rst offense of individual traffi cking is punishable by up to twenty years in prison and/or a fi ne of up to $1 million for an individual or up to $5 million for other than individuals. The table summarizes the control mechanisms and penalties for each schedule of the Controlled Substances Act.

The Controlled Substances Act also stipulates that an offense involving a controlled substance analog—a chemical substance sub- stantially similar in chemical structure to a controlled substance— triggers penalties as if it were a controlled substance listed in schedule  I. This section is designed to combat the proliferation of so-called designer drugs —substances that are chemically related to some controlled drugs and are pharmacologically very potent. These substances are manufactured by skilled individuals in clandestine lab- oratories with the knowledge that their products will not be covered by the schedules of the Controlled Substances Act. For instance, fen- tanyl is a powerful narcotic that is commercially marketed for medical

use and is also listed as a controlled dangerous substance. This drug is about one hundred times as potent as morphine. A number of sub- stances chemically related to fentanyl have been synthesized by un- derground chemists and sold on the street. The fi rst such substance we know of was sold under the street name China White. These drugs have been responsible for more than a hundred overdose deaths in California and nearly twenty deaths in western Pennsylvania. As de- signer drugs such as China White become identifi ed by drug offi cials and linked to drug abuse, they are placed in appropriate schedules.

The Controlled Substances Act also refl ects an effort to de- crease the prevalence of clandestine drug laboratories designed to manufacture controlled substances. The act regulates the manufacture and distribution of precursors, the chemical compounds used by clan- destine drug laboratories to synthesize abused drugs. Targeted pre- cursor chemicals are listed in the defi nition section of the Controlled Substances Act. Severe penalties are assigned to a person who possesses a listed precursor chemical with the intent to manufacture a controlled substance or who possesses or distributes a listed chemical knowing, or having reasonable cause to believe, that the listed chemi- cal will be used to manufacture a controlled substance. In addition, precursors to PCP, amphetamines, and methamphetamines are enu- merated specifi cally in schedule II, making them subject to regulation in the same manner as other schedule II substances.

IMPORT–EXPORT      

Narcotic Nonnarcotic Security Manufacturer/Distributor Reports to Drug Enforcement Administration

Criminal Penalties for Individual Traffi cking (First Offense)

Permit Permit Vault/safe Yes 0–20 years/$1 million Permit Permit Vault/safe Yes 0–20 years/$1 million Permit Declaration Secure storage

area Yes, narcotic; no, nonnarcotic 0–5 years/$250,000

Permit Declaration Secure storage area

Manufacturer only, narcotic; no, nonnarcotic

0–3 years/$250,000

Permit to import; dec- laration to export

Declaration Secure storage area

Manufacturer only, narcotic; no,

nonnarcotic 0–1 year/$100,000

Source: Drug Enforcement Administration, Washington, DC

the diffi cult analytical chore facing the forensic chemist, consider the com- plexity of the drug preparations themselves. Usually these contain active drug ingredients of unknown origin and identity, as well as additives—for example, sugar, starch, and quinine—that dilute their potency and stretch their value on the illicit-drug market. Do not forget that illicit-drug dealers are not hampered by government regulations that ensure the quality and consistency of their product.

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When a forensic chemist picks up a drug specimen for analysis, he or she can expect to fi nd just about anything, so all contingencies must be prepared for. The analysis must leave no room for error because its results will have a direct bearing on the process of determining the guilt or innocence of a defen- dant. There is no middle ground in drug identifi cation—either the specimen is a specifi c drug or it is not—and once a positive conclusion is drawn, the chemist must be prepared to support and defend the validity of the results in a court of law.

SCREENING AND CONFIRMATION

The challenge or diffi culty of forensic drug identifi cation comes in select- ing analytical procedures that will ensure a specifi c identifi cation of a drug. Presented with a substance of unknown origin and composition, the foren- sic chemist must develop a plan of action that will ultimately yield the drug’s identity. This plan, or scheme of analysis, is divided into two phases.

First, faced with the prospect that the unknown substance may be any one of a thousand or more commonly encountered drugs, the analyst must employ screening tests to reduce these possibilities to a small and manage- able number. This objective is often accomplished by subjecting the material to a series of color tests that produce characteristic colors for the more com- monly encountered illicit drugs. Even if these tests produce negative results, their value lies in having excluded certain drugs from further consideration.

Once the number of possibilities has been reduced substantially, the second phase of the analysis must be devoted to pinpointing and confi rming the drug’s identity. In an era in which crime laboratories receive voluminous quantities of drug evidence, it is impractical to subject a drug to all the chemi- cal and instrumental tests available. Indeed, it is more realistic to look on these techniques as constituting a large analytical arsenal. The chemist, aided by training and experience, must choose tests that will most conveniently identify a particular drug.

Forensic chemists often use a specifi c test to identify a drug substance to the exclusion of all other known chemical substances. A single test that identifi es a substance is known as a confi rmation . The analytical scheme sometimes consists of a series of nonspecifi c or presumptive tests. Each test in itself is insuffi cient to prove the drug’s identity; however, the proper analytical scheme encompasses a combination of test results that characterize one and only one chemical substance—the drug under investigation. Furthermore, experimental evidence must confi rm that the probability of any other sub- stance responding in an identical manner to the scheme selected is so small as to be beyond any reasonable scientifi c certainty.

Another consideration in selecting an analytical technique is the need for either a qualitative or a quantitative determination. The former relates just to the identity of the material, whereas the latter refers to the percentage of each component in the mixture. Hence, a qualitative identifi cation of a powder may reveal the presence of heroin and quinine, whereas a quantitative analysis may conclude the presence of 10 percent heroin and 90 percent quinine.

Obviously, a qualitative identifi cation must precede any attempt at quan- titation; there is little value in attempting to quantitate a material without fi rst determining its identity. Essentially, a qualitative analysis of a material requires the determination of numerous properties using a variety of analyti- cal techniques. On the other hand, a quantitative measurement is usually ac- complished by precise measurement of a single property of the material.

Forensic chemists normally rely on several tests for a routine drug- identifi cation scheme: color tests, microcrystalline tests, chromatography, spectrophotometry, and mass spectrometry.

screening test A preliminary test used to reduce the number of possible identities of an unknown substance.

confi rmation A single test that specifi cally identifi es a substance.

312

DRUGS

COLOR TESTS

Many drugs yield characteristic colors when brought into contact with specifi c chemical reagents. Not only do these tests provide a useful indicator of a drug’s presence, but they are also used by investigators in the fi eld to examine materials suspected of contain- ing a drug (see Figure 12 ). However, color tests are useful for screening purposes only and are never taken as conclusive identifi cation of unknown drugs.

Five primary color-test reagents are as follows:

1. Marquis. The reagent turns purple in the presence of heroin and morphine and most opium deriva- tives. Marquis becomes orange-brown when mixed with amphetamines and methamphetamines.

2. Dillie-Koppanyi. This is a valuable screening test for barbiturates, in whose presence the reagent turns a violet-blue color.

3. Duquenois-Levine. This is a valuable color test for marijuana, performed by adding a series of chemical solutions to the suspect vegetation. A positive result is shown by a purple color when chloroform is added.

4. Van Urk. The reagent turns blue-purple in the presence of LSD. However, owing to the extremely small quantities of LSD in illicit preparations, this test is diffi cult to conduct under fi eld conditions.

5. Scott Test. This is a color test for cocaine. A powder containing cocaine turns a cobalt thiocyanate solution blue. Upon the addition of hydrochloric acid, the blue color is transformed to a clear pink color. Upon the addi- tion of chloroform, if cocaine is present, the blue color reappears in the chloroform layer.

MICROCRYSTALLINE TESTS

A technique considerably more specifi c than color tests is the microcrystalline test . A drop of a chemical reagent is added to a small quantity of the drug on a microscopic slide. After a short time, a chemical reaction ensues, producing a crystalline precipitate. The size and shape of the crystals, examined under a compound microscope, reveal the identity of the drug. Crystal tests for cocaine and methamphetamine are illustrated in Figure 13 .

FIGURE 12 A fi eld color-test kit for cocaine. The suspect drug is placed in the plastic pouch. Tubes containing chemicals are broken open, and the color of the chemical reaction is observed. Courtesy Tri-Tech, Inc., Southport, NC, www.tritechusa.com

microcrystalline test A test that identifi es a specifi c substance based on the color and shape of crystals formed when the substance is mixed with specifi c reagents.

(a) (b)

FIGURE 13 (a) A photomicrograph of a cocaine crystal formed in platinum chloride (400�). (b) A photomicrograph of a methamphetamine crystal formed in gold chloride (400�). San Bernardino County Sheriff

313

DRUGS

Over the years, analysts have developed hundreds of crystal tests to characterize the most commonly abused drugs. These tests can be rapidly executed and often do not require the isolation of a drug from its diluents; how- ever, because diluents can sometimes alter or modify the shape of the crystal, the examiner must develop experience in interpreting the results of the test.

Most color and crystal tests are largely empirical—that is, scientists do not fully understand why they produce the results they do. From the forensic chemist’s point of view, this is not important. When the tests are properly cho- sen and used in proper combination, they reveal characteristics that identify the substance as a certain drug to the exclusion of all others.

Quick Review • Analysts use screening tests to determine the identity of drugs present in

a sample. These tests reduce the number of possible drugs to a small and manageable number.

• A series of color tests produce characteristic colors for the more com- monly encountered illicit drugs. In a microcrystalline test, a drop of a chemical reagent added to a small quantity of drug on a microscope slide produces crystals highly characteristic of a drug.

• After preliminary testing, forensic chemists use more specifi c tests to identify a drug substance to the exclusion of all other known chemical substances.

CHROMATOGRAPHY

Chromatography is a means of separating and tentatively identifying the components of a mixture. It is particularly useful for analyzing drug speci- mens, which may be diluted with practically any material to increase the quan- tity of the product available to prospective customers. The task of identifying an illicit-drug preparation would be arduous without the aid of chromato- graphic methods to fi rst separate the mixture into its components.

THIN-LAYER CHROMATOGRAPHY Thin-layer chromatography (TLC) uses a solid stationary phase and a moving liquid phase to separate the constituents of a mixture. Thin-layer chromatography is a powerful tool for solving many of the analytical problems presented to the forensic scientist. The method is both rapid and sensitive; moreover, less than 100 micrograms of suspect mate- rial is required for the analysis. In addition, the equipment necessary for TLC work has minimal cost and space requirements. Importantly, numerous sam- ples can be analyzed simultaneously on one thin-layer plate. This technique is principally used to detect and identify components in complex mixtures.

In TLC, the components of a suspect mixture are separated as they travel up a glass or plastic plate, eventually appearing as a series of dark or colored spots on the plate. This action is then compared to a standard sample separa- tion of a specifi c drug, such as heroin. If both the standard and the suspect substances travel the same distance up the plate, they can tentatively be identi- fi ed as being the same substance.

A thin-layer plate is prepared by coating a glass plate or plastic backing with a thin fi lm of a granular material, usually silica gel or aluminum oxide. This granular material serves as the solid stationary phase and is usually held in place on the plate with a binding agent such as plaster of paris. If the sample to be analyzed is a solid, it must fi rst be dissolved in a suitable solvent, then a few microliters of the solution is spotted with a capillary tube onto the granular sur- face near the lower edge of the plate. A liquid sample may be applied directly to the plate in the same manner. The plate is then placed upright in a closed cham- ber that contains a selected liquid, but the liquid must not touch the sample spot.

chromatography Any of several analytical techniques for separating organic mixtures into their components by attraction to a stationary phase while being propelled by a moving phase.

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The liquid slowly rises up the plate by capillary action. This rising liquid is the moving phase in thin-layer chromatography. As the liquid moves past the sample spot, the components of the sample become distributed between the stationary solid phase and the moving liquid phase. The components with the greatest affi nity for the moving phase travel up the plate faster than those that have greater affi nity for the stationary phase. When the liquid front has moved a suffi cient distance (usually 10  centimeters), the development is complete, and the plate is removed from the chamber and dried (see Figure 14 ). An ex- ample of the chromatographic separation of ink is shown in Figure 15 .

Often the plate is sprayed with a chemical reagent that reacts with the separated substances and causes them to form colored spots. Figure 16 shows the chromatogram of a marijuana extract that has been separated into its components by TLC and visualized by having been sprayed with a chemical reagent.

Figure 17 shows a sample suspected of containing heroin and quinine that has been chromatographed alongside known heroin and quinine standards. The distance the unknown material migrated up the sus- pect plate is compared to the distances that heroin and quinine migrated up a standard sample plate. If the distances are the same, a tentative identifi cation can be made. However, such an identifi cation can- not be considered defi nitive because numerous other substances can migrate the same distance up the plate when chromatographed under similar condi- tions. Thus, thin-layer chromatography alone cannot provide an absolute identifi cation; it must be used in conjunction with other testing procedures to prove absolute identity.

GAS CHROMATOGRAPHY (GC) Gas chromatography (GC) separates mixtures based on their distribution

Sample spot

Very thin coating of silica gel or aluminum oxide

(a)

(b)

Rising solvent; original spot has separated into several spots

FIGURE 14 (a) In thin-layer chromatography, a liquid sample is spotted onto the granular surface of a gel-coated plate. (b) The plate is placed into a closed chamber that contains a liquid. As the liquid rises up the plate, the components of the sample distribute themselves between the coating and the moving liquid. The mixture is separated, with substances with a greater affi nity for the moving liquid traveling up the plate at a faster speed.

FIGURE 15 (a) In thin-layer chromatography, the liquid phase begins to move up the stationary phase. (b) Liquid moves past the ink spot carrying the ink components up the stationary phase. (c) The moving liquid has separated the ink into its several components. Richard Megna\ Fundamental Photographs, NYC

(a) (b) (c) 315

DRUGS

FIGURE 16 A thin-layer chromatogram of a marijuana extract. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

FIGURE 17 Chromatographs of known heroin (1) and quinine (2) standards along- side a suspect sample (3). Richard Saferstein

between a stationary liquid phase and a moving gas phase. In gas chroma- tography, the moving phase is called the carrier gas , which fl ows through a column constructed of glass. The stationary phase is a thin fi lm of liquid within the column, which is known as a capillary column.

Capillary columns are composed of glass and are 15 to 60 meters in length. These types of columns are very narrow, ranging from 0.25 to 0.75 millimeter in diameter. Capillary columns can be made narrow because their stationary liquid phase is actually a very thin fi lm coating the column’s inner wall.

As the carrier gas fl ows through the capillary column, it carries with it the components of a mixture that have been injected into the column. Com- ponents with a greater affi nity for the moving gas phase travel through the column more quickly than those with a greater affi nity for the stationary liquid phase. Eventually, after the mixture has traversed the length of the column, it emerges separated into its components.

The time required for a component to emerge from the column after its injection into the column is known as the retention time, which is a useful identifying characteristic. Figure 18(a) shows the chromatogram of two bar- biturates; each barbiturate has tentatively been identifi ed by comparing its retention time to those of known barbiturates, shown in Figure 18(b) . How- ever, because other substances may have comparable retention times under

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similar chromatographic conditions, gas chromatography cannot be consid- ered an absolute means of identifi cation. Conclusions derived from this tech- nique must be confi rmed with other testing procedures.

Gas chromatography is widely used because of its ability to resolve a highly complex mixture into its components, usually within minutes. It has the added advantages of being extremely sensitive and yielding quantitative

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1

3

2

4

56

7

8

1. Sample

2. Injector

3. Carrier gas

4. Column

5. Detector

6. Power supply

7. Recorder

8. Chromatogram

Basic gas chromatography. Gas chromatography permits rapid separation of complex mixtures into individual compounds and allows identifi cation and quantitative determination of each compound. As shown, a sample is introduced by a syringe (1) into a heated injection chamber (2). A constant stream of nitrogen gas (3) fl ows through the injector, carrying the sample into the column (4), which contains a thin fi lm of liquid. The sample is separated in the column, and the carrier gas and separated components emerge from the column and enter the detector (5). Signals developed by the detector activate the recorder (7), which makes a permanent record of the separation by tracing a series of peaks on the chromatograph (8). The time it takes a component to emerge from the column identifi es the component present, and the peak area identifi es the concentration. Courtesy Varian Inc., Palo Alto, CA

CLOSER ANALYSIS THE GAS CHROMATOGRAPH

A simplifi ed scheme of the gas chromatograph is shown in the fi gure. The operation of the instrument can be summed up briefl y as follows: The carrier gas is fed into the column at a constant rate. The carrier gas, generally nitrogen or helium, is chemically inert. The sample un- der investigation is injected as a liquid into a heated injection port with a syringe, where it is immediately vaporized and swept into the column by the carrier gas. The column itself is heated in an oven in order to keep the sample in a vapor state as it travels through the column. In the column, the components of the sample travel in the di- rection of the carrier gas fl ow at speeds that are determined by their distribution between the stationary and moving phases. If the analyst

has selected the proper liquid phase and has made the column long enough, the components of the sample will be completely separated as they emerge from the column.

As each component emerges from the column, it enters a detec- tor. One type of detector uses a fl ame to ionize the emerging chemical substance, thus generating an electrical signal. The signal is recorded on a strip-chart recorder as a function of time. This written record of the separation is called a chromatogram. A gas chromatogram is a plot of the recorder response (on the vertical axis) over time (on the horizontal axis). A typical chromatogram shows a series of peaks, each of which corresponds to one component of the mixture.

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0 1 2 3 4 5 6 7 8 9 10 11 12

0 1 2 3 4 5 6 7 8 9 10 11 12

Pentobarbital

Secobarbital

TIME (MINUTES) (a)

Butabarbital

Amobarbital

Pentobarbital

Secobarbital

Phenobarbital

TIME (MINUTES) (b)

FIGURE 18 (a) An unknown mixture of barbiturates is identifi ed by comparing its retention times to (b), a known mixture of barbiturates. Courtesy Varian Inc., Palo Alto, CA

results. Gas chromatography has suffi cient sensitivity to detect and quantitate materials down to the nanogram (i.e., 0.000000001 gram).

SPECTROPHOTOMETRY

The technique of chromatography is particularly suited for analyzing illicit drugs because it can separate a drug from other substances that may be pres- ent in the drug preparation. However, chromatography has the drawback of

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not being able to specifi cally identify the material under investigation. For this reason, other analytical tools are frequently used to identify drugs. These include the technique of spectrophotometry , which can identify a substance by exposing it to a specifi c type of electromagnetic radiation.

THEORY OF LIGHT The knowledge of the nature and behavior of light is fundamental to understanding physical properties important to the examina- tion of forensic evidence. One can think of light as a continuous wave. The wave concept depicts light as having the up-and-down motion of a continuous wave, as shown in Figure 19 . Such a wave can be characterized by two distinct properties: wavelength and frequency. The distance between two consecutive crests (high points) or troughs (low points) of a wave is called the wavelength ; it is designated by the Greek letter lambda (�) and is typically measured in nanometers (nm), or millionths of a meter. The number of crests (or troughs) passing any one given point in a unit of time is defi ned as the frequency of the wave. Frequency is normally designated by the letter f and is expressed in cycles per second (cps). Frequency and wavelength are inversely propor- tional to one another, as shown by the relationship expressed in the following equation:

F � c �

In this equation, c represents the speed of light. Many of us have held a glass prism up toward the sunlight and watched it

transform light into the colors of the rainbow. The process of separating light into its component colors is called dispersion . Visible light usually travels at a constant velocity of nearly 300 million meters per second. However, on pass- ing through the glass of a prism, each color component of light is slowed to a speed slightly different from those of the others, causing each component to bend at a different angle as it emerges from the prism (see Figure 20 ). This bending of light waves results in a change in velocity called refraction .

The observation that a substance has a color is consistent with this de- scription of white light. For example, when light passes through a red glass, the glass absorbs all the component colors of light except red, which passes through or is transmitted by the glass. Likewise, one can determine the color of an opaque object by observing its ability to absorb some of the component

λ

λ

FIGURE 19 The frequency of the lower light wave is twice that of the upper wave.

spectrophotometry An analytical method for identifying a substance by its selective absorption of different wavelengths of light.

wavelength The distance between crests of adjacent waves.

frequency The number of waves that pass a given point per unit of time.

dispersion The separation of light into its component wavelengths.

refraction The bending of a light wave caused by a change in its velocity.

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colors of light while refl ecting others back to the eye. Color is thus a visual indication that objects absorb certain portions of visible light and transmit or refl ect others. Scientists have long recognized this phenomenon and have learned to characterize chemical substances by the type and quantity of light they absorb. This has important implications for the identifi cation and clas- sifi cation of forensic evidence.

ELECTROMAGNETIC SPECTRUM Visible light is only a small part of a large family of radiation waves known as the electromagnetic spectrum (see Fig- ure 21 ). All electromagnetic waves travel at the speed of light ( c ) and are distin- guishable from one another only by their different wavelengths or frequencies. Hence, the only property that distinguishes X-rays from radio waves is the different frequencies the two types of waves possess.

Similarly, the range of colors that make up the visible spectrum can be correlated with frequency. For instance, the lowest frequencies of visible light are red; waves with a lower frequency fall into the invisible infrared (IR) region. The highest frequencies of visible light are violet; waves with a higher frequency extend into the invisible ultraviolet (UV) region. No defi nite bound- aries exist between any colors or regions of the electromagnetic spectrum; instead, each region is composed of a continuous range of frequencies, each blending into the other.

Just as a substance can absorb visible light to produce color, many of the invisible radiations of the electromagnetic spectrum are likewise absorbed. This absorption phenomenon is the basis for spectrophotometry, an analytical

Visible light

Gamma rays

High frequency Low frequency

Short wavelength Energy increases

Long wavelength

X rays Ultraviolet Infrared Microwaves Radio waves

FIGURE 21 The electromagnetic spectrum.

X-ray A high-energy, short-wavelength form of electromagnetic radiation.

visible light Colored light ranging from red to violet in the electromagnetic spectrum.

electromagnetic spectrum The entire range of radiation energy from the most energetic cosmic rays to the least energetic radio waves.

White light

Slit

Prism

Screen

Red

Violet

Red

Violet

Orange Yellow

Green Blue

FIGURE 20 A representation of the dispersion of light by a glass prism.

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technique that measures the quantity of radiation that a particular material absorbs as a function of wavelength or frequency.

THE SPECTROPHOTOMETER An object does not absorb all the visible light it is exposed to; instead, it selectively absorbs some frequencies and refl ects or transmits others. Similarly, the absorption of other types of electromagnetic radiation by chemical substances is also selective. Selective absorption of a substance is measured by an instrument called a spectrophotometer, which produces a graph or absorption spectrum that depicts the absorption of light as a function of wavelength or frequency.

The spectrophotometer measures and records the absorption spectrum of a chemical. The basic components of a simple spectrophotometer are the same regardless of whether it is designed to measure the absorption of UV, visible, or IR radiation. These components are illustrated diagrammatically in Figure 22 . They include (1) a radiation source, (2) a monochromator or frequency se- lector, (3) a sample holder, (4) a detector to convert electromagnetic radiation into an electrical signal, and (5) a recorder to produce a record of the signal.

The measuring absorption of UV, visible, and IR radiation is particularly applicable to obtaining qualitative data pertaining to the identifi cation of drugs.

ULTRAVIOLET AND VISIBLE SPECTROPHOTOMETRY Ultraviolet (UV) and visible spectrophotometry measure the absorption of UV and visible light as a function of wavelength or frequency. For example, the UV absorption spectrum of heroin shows a maximum absorption band at a wavelength of 278 nanometers (see Figure 23 ). This shows that the simplicity of a UV spec- trum facilitates its use as a tool for determining a material’s probable identity. For instance, a white powder may have a UV spectrum comparable to heroin and therefore may be tentatively identifi ed as such. (Fortunately, sugar and starch, common diluents of heroin, do not absorb UV light.)

This technique, however, does not provide a defi nitive result; other drugs or materials may have a UV absorption spectrum similar to that of heroin. Nevertheless, UV spectrophotometry is often useful in establishing the prob- able identity of a drug. For example, if an unknown substance yields a UV spectrum that resembles that of amphetamine (see Figure 24 ), thousands of substances are immediately eliminated from consideration, and the analyst can begin to identify the material from a relatively small number of possibili- ties. A comprehensive collection of UV drug spectra provides an index that can rapidly be searched in order to tentatively identify a drug or, failing that, at least to exclude certain drugs from consideration.

ultraviolet Invisible long frequencies of light beyond violet in the visible spectrum.

Detector Radiation source Monochromator

Prism

Sample cell

Slit

Recorder

Recorder translates electrical signal into recording of the absorption spectrum

The absorption spectrum of a chemical substance allows spectrophotometry to be used for identification.

FIGURE 22 The parts of a simple spectrophotometer.

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DRUGS

INFRARED SPECTROPHOTOMETRY In contrast to the simplicity of a UV spec- trum, absorption in the infrared (IR) region provides a far more complex pat- tern. Figure 25 depicts the IR spectra of heroin and secobarbital. Here, the absorption bands are so numerous that each spectrum can provide enough characteristics to identify a substance specifi cally. Different materials always have distinctively different infrared spectra; each IR spectrum is therefore equivalent to a “fi ngerprint” of that substance and no other. This technique is one of the few tests available to the forensic scientist that can be considered specifi c in itself for identifi cation. The IR spectra of thousands of organic compounds have been collected, indexed, and cataloged as invalu- able references for identifying organic substances. The selective absorption of light by drugs in the UV and IR regions of the electromagnetic spectrum provides a valuable technique for characterizing drugs.

MASS SPECTROMETRY

The Gas Chromatography section discussed the operation of the gas chro- matograph. This instrument is one of the most important tools in a crime laboratory. Its ability to separate the components of a complex mixture is unsurpassed. However, gas chromatography has one important drawback: its inability to produce specifi c identifi cation. A forensic chemist cannot un- equivocally state the identity of a substance based solely on its retention time as determined by the gas chromatograph. Fortunately, by coupling the gas chromatograph to a mass spectrometer, forensic chemists have largely over- come this problem.

A mixture’s components are fi rst separated on the gas chromatograph. A direct connection between the gas chromatograph column and the mass spectrometer then allows each component to fl ow into the spectrometer as

Heroin

Ab so

rb an

ce

250 300 350 Wavelength in nanometers

FIGURE 23 The ultraviolet spectrum of heroin.

Amphetamine

Ab so

rb an

ce

250 300 350 Wavelength (nanometers)

FIGURE 24 The ultraviolet spectrum of an amphetamine.

infrared Invisible short frequencies of light before red in the visible spectrum.

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DRUGS

it emerges from the gas chromatograph. In the mass spectrometer, the mate- rial enters a high-vacuum chamber where a beam of high-energy electrons is aimed at the sample molecules. The electrons collide with the molecules, causing them to lose electrons and to acquire a positive charge. These posi- tively charged molecules, or ions , are very unstable or are formed with excess energy and almost instantaneously decompose into numerous smaller frag- ments. The fragments then pass through an electric or magnetic fi eld, where they are separated according to their masses. The unique feature of mass

0.00

100.00 %T

4000 3500 3000 2500 2000 1500 1000 500 Wavenumber cm–1

0.00

100.00 %T

4000 3500 3000 2500 2000 1500 1000 500 Wavenumber cm–1

FIGURE 25 (a) The infrared spectrum of heroin. (b) The infrared spectrum of secobarbital.

ion An atom or molecule bearing a positive or negative charge.

(a)

(b)

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spectrometry is that, under carefully controlled conditions, no two substances produce the same fragmentation pattern. In essence, one can think of this pattern as a “fi ngerprint” of the substance being examined (see Figure 26 ).

Mass spectrometry thus provides a specifi c means for identifying a chemical structure. It is also sensitive to minute concentrations. Mass spectrometry is widely used to identify drugs; however, further research is expected to yield sig- nifi cant applications for identifying other types of physical evidence. Figure 27 illustrates the mass spectra of heroin and cocaine; here, each line rep- resents a fragment of a different mass (actually the ratio of mass to charge), and the line height refl ects the relative abundance of each fragment. Note how different the fragmentation patterns of heroin and cocaine are. Each mass spectrum is unique to each drug and therefore provides a spe- cifi c test for identifying that substance.

The combination of the gas chromatograph and mass spectrometer (GC/MS) is further enhanced when a computer is added to the sys- tem. The integrated gas chromatograph/mass

spectrometer/computer system provides the ultimate in speed, accuracy, and sensitivity. With the ability to record and store in its memory several hundred

D

C

B

A

A B

C

D

Chromatogram Spectra

Separation Identification

GC MS

FIGURE 26 How GC/MS works. Left to right, the sample is separated into its components by the gas chromatograph, and then the components are ionized and identifi ed by characteristic fragmentation patterns of the spectra produced by the mass spectrometer. Courtesy Agilent Technologies, Inc., Palo Alto, CA

43

94 146

204 215

268

327

369

100 200 300 Mass/charge

(a)

Ab un

da nc

e

42

122 150

182

272

82

303

100 150 300 Mass/charge

(b)

Ab un

da nc

e

250 200 50

FIGURE 27 (a) The mass spectrum of heroin. (b) The mass spectrum of cocaine.

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1. Injection port 3. Ion source

4. Quadrupole 6. Data system

5. Detector 2. GC column

FIGURE 28 A tabletop mass spectrometer. (1) The sample is injected into a heated inlet port, and carrier gas sweeps it into the column. (2) The GC column separates the mixture into its components. (3) In the ion source, a fi lament wire emits electrons that strike the sample molecules, causing them to fragment as they leave the GC column. (4) The quadrupole, consisting of four rods, separates the fragments according to their mass. (5) The detector counts the fragments passing though the quadrupole. The signal is small and must be amplifi ed. (6) The data system is responsible for total control of the entire GC/MS system. It detects and measures the abundance of each fragment and displays the mass spectrum. Courtesy Agilent Technologies, Inc., Palo Alto, CA

mass spectra, such a system can detect and identify substances present in quantities of only one millionth of a gram. Furthermore, the computer can be programmed to compare an unknown spectrum against a comprehen- sive library of mass spectra stored in its memory. The advent of personal computers and microcircuitry has enabled the design of mass spectrometer systems that can fi t on small tables. Such a unit is pictured in Figure 28 . With data obtained from a GC/MS determination, a forensic analyst can, with one instrument, separate the components of a complex drug mixture and then unequivocally identify each substance present in the mixture.

Research-grade mass spectrometers are found in laboratories as larger, fl oor-model units (see Figure 29 ).

Quick Review • Chromatography is a means of separating and

tentatively identifying the components of a mixture.

• Thin-layer chromatography (TLC) uses a solid stationary phase, usually coated onto a glass plate, and a mobile liquid phase to separate the components of the mixture.

• Gas chromatography (GC) separates mixtures on the basis of their distribution between a sta- tionary liquid phase and a mobile gas phase.

• Spectrophotometry is the measurement of the absorption of light by chemical substances.

• Dispersion is the process of separating light into its component colors. Each component bends, or refracts, at a different angle as it emerges from the prism. The large family of radiation waves is known as the electromagnetic spectrum.

FIGURE 29 A scientist injecting a sample into a research-grade mass spectrometer. Geoff/Tompkinson/Science Photo Library\Photo Researchers, Inc.

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• Most forensic laboratories use ultraviolet (UV) and infrared (IR) spectro- photometers to characterize chemical compounds.

• IR spectrophotometry provides a far more complex pattern than UV spec- trophotometry. Because different materials have distinctively different in- frared spectra, each IR spectrum is equivalent to a “fi ngerprint” of that substance.

• Mass spectrometry characterizes organic molecules by observing their fragmentation pattern after their collision with a beam of high-energy electrons.

• Infrared spectrophotometry and mass spectrophotometry typically are used to identify a specifi c drug substance.

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CHAPTER REVIEW

• A drug is a natural or synthetic substance that is used to produce physiological or psychological effects in humans or other animals.

• Nondrug factors that play a part in drug dependence include the personal characteristics of the user, his or her expecta- tions about the drug experience, society’s attitudes toward and possible responses to the drug, and the setting in which the drug is used.

• Physical dependence is defi ned as a physiological need for a drug that has been brought about by its regular use. Psycho- logical dependence is the conditioned use of a drug caused by underlying emotional needs.

• Narcotic drugs are analgesics, meaning that they relieve pain by depressing the central nervous system.

• The most common source for narcotic drugs is opium. Mor- phine is extracted from opium and used to synthesize heroin.

• Opiates are not derived from opium or morphine, but they have the same physiological effects on the body. Examples of opiates are methadone and OxyContin (i.e., oxycodone).

• Hallucinogens cause marked changes in normal thought pro- cesses, perceptions, and moods. Marijuana is the most well- known drug in this class. Other hallucinogens include LSD, mescaline, PCP, psilocybin, and MDMA (or Ecstasy).

• Depressants decrease the activity of the central nervous system, calm irritability and excitability, and produce sleep. Depressants include alcohol (i.e., ethanol), barbiturates, tran- quilizers, and various substances that can be sniffed such as airplane glue and model cement.

• Stimulants increase the activity of the central nervous system and are taken to increase alertness and activity. Stimulants

include amphetamines, sometimes known as “uppers” or “speed,” and cocaine, which in its freebase form is known as ”crack.”

• Club drugs are synthetic drugs that are used at nightclubs, bars, and raves (i.e., all-night dance parties). Some club drugs act as stimulants; others have depressant effects.

• Anabolic steroids are synthetic compounds that are chemi- cally related to the male sex hormone testosterone. Anabolic steroids are often abused by individuals who are interested in accelerating muscle growth.

• Federal law establishes fi ve schedules of classifi cation for controlled dangerous substances on the basis of a drug’s potential for abuse, potential for physical and psychological dependence, and medical value.

• The packaging of drug evidence must prevent loss and/or cross-contamination of the contents, and often the original container in which the drug was seized is used. Specimens suspected of containing volatile solvents must be packaged in an airtight container to prevent evaporation.

• The investigator may help in the identifi cation of the drug by supplying to the drug analyst any background information that may relate to the drug’s identity.

• Analysts use screening tests to determine the identity of drugs present in a sample. These tests reduce the number of possible drugs to a small and manageable number.

• A series of color tests produce characteristic colors for the more commonly encountered illicit drugs. In a microcrystal- line test, a drop of a chemical reagent added to a small quan- tity of drug on a microscope slide produces crystals highly characteristic of a drug.

326

• After preliminary testing, forensic chemists use more specifi c tests to identify a drug substance to the exclusion of all other known chemical substances.

• Chromatography is a means of separating and tentatively identifying the components of a mixture.

• Thin-layer chromatography (TLC) uses a solid stationary phase, usually coated onto a glass plate, and a mobile liquid phase to separate the components of the mixture.

• Gas chromatography (GC) separates mixtures on the basis of their distribution between a stationary liquid phase and a mobile gas phase.

• Spectrophotometry is the measurement of the absorption of light by chemical substances.

• Dispersion is the process of separating light into its compo- nent colors. Each component bends, or refracts, at a different

angle as it emerges from the prism. The large family of radia- tion waves is known as the electromagnetic spectrum.

• Most forensic laboratories use ultraviolet (UV) and infra- red (IR) spectrophotometers to characterize chemical com- pounds.

• IR spectrophotometry provides a far more complex pattern than UV spectrophotometry. Because different materials have distinctively different infrared spectra, each IR spectrum is equivalent to a “fi ngerprint” of that substance.

• Mass spectrometry characterizes organic molecules by ob- serving their fragmentation pattern after their collision with a beam of high-energy electrons.

• Infrared spectrophotometry and mass spectrophotometry typically are used to identify a specifi c drug substance.

KEY TERMS

anabolic steroids

analgesic

chromatography

confi rmation

depressant

dispersion

electromagnetic spectrum

frequency

hallucinogen

infrared

ion

microcrystalline test

narcotic

physical dependence

psychological dependence

refraction

screening test

spectrophotometry

stimulant

ultraviolet

visible light

wavelength

X-ray

DRUGS

REVIEW QUESTIONS

1. A(n) ______________ can be defi ned as a natural or syn- thetic substance that is used to produce physiological or psy- chological effects in humans or other animals.

2. True or False: Underlying emotional factors are the pri- mary motives leading to the repeated use of a drug. ______________

3. True or False: Drugs such as alcohol, heroin, amphetamines, barbiturates, and cocaine can lead to a low degree of psycho- logical dependence with repeated use. ______________

4. The development of ______________ dependence on a drug is shown by withdrawal symptoms such as convulsions when the user stops taking the drug.

5. True or False: Abuse of barbiturates can lead to physical dependency. ______________

6. True or False: Repeated use of LSD leads to physical depen- dency. ______________

7. Physical dependency develops only when the drug user adheres to a(n) ______________ schedule of drug intake.

8. Narcotic drugs are ______________ that have ______________ effects on the central nervous system.

9. ______________ is a gummy, milky juice exuded from cuts made on the unripe pods of the Asian poppy.

10. ______________ is a chemical derivative of morphine made by reacting morphine with acetic anhydride.

11. A legally available drug that is chemically related to heroin and heavily used is ______________ .

12. True or False: Methadone is classifi ed as a narcotic drug, even though it is not derived from opium or morphine. ______________

13. Drugs that cause marked alterations in mood, attitude, thought processes, and perceptions are called ______________ .

14. ______________ is the sticky resin extracted from the mar- ijuana plant.

15. The active ingredient of marijuana largely responsible for its hallucinogenic properties is ______________ .

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DRUGS

16. True or False: The potency of a marijuana preparation depends on the proportion of the various plant parts in the mixture. ______________

17. The marijuana preparation with the highest THC content is ______________ .

18. LSD is a chemical derivative of ______________ , a chemi- cal obtained from the ergot fungus that grows on certain grasses and grains.

19. The drug phencyclidine is often manufactured for the illicit- drug market in ______________ laboratories.

20. True or False: Alcohol depresses the central nervous system. ______________

21. ______________ are called “downers” because they depress the central nervous system.

22. True or False: Phenobarbital is an example of a long-acting barbiturate. ______________

23. ______________ is a powerful sedative and muscle relax- ant that possesses many of the depressant properties of bar- biturates.

24. ______________ and ______________ drugs are used to relieve anxiety and tension without inducing sleep.

25. True or False: Huffi ng volatile solvents stimulates the central nervous system. ______________

26. ______________ are a group of synthetic drugs that stimu- late the central nervous system.

27. ______________ is extracted from the leaf of the coca plant.

28. Traditionally, cocaine is ______________ into the nostrils.

29. True or False: Cocaine is a powerful central nervous system depressant. ______________

30. The two drugs usually associated with drug-facilitated sexual assaults are ______________ and ______________ .

31. ______________ steroids are designed to promote muscle growth but have harmful side effects.

32. Federal law establishes ______________ schedules of clas- sifi cation for the control of dangerous drugs.

33. Drugs that have no accepted medical use are placed in schedule ______________ .

34. Librium and Valium are listed in schedule ______________ .

35. True or False: Color tests are used to identify drugs conclu- sively. ______________

36. The ______________ color-test reagent turns purple in the presence of heroin.

37. The Duquenois-Levine test is a valuable color test for ______________ .

38. The ______________ test is a widely used color test for cocaine.

39. ______________ tests tentatively identify drugs by the size and shape of crystals formed when the drug is mixed with specifi c reagents.

40. A technique that uses a moving liquid phase and a stationary solid phase to separate mixtures is ______________ .

41. True or False: Thin-layer chromatography yields the positive identifi cation of a material. ______________

42. The distance between two successive identical points on a wave is known as ______________ .

43. The process of separating light into its component colors is called ______________ .

44. True or False: Color is an indication that substances selec- tively absorb light. ______________

45. Visible light and X-rays are only part of the family of known radiation waves known as the ______________ .

46. Red light is (higher, lower) in frequency than violet light.

47. The selective absorption of electromagnetic radiation by materials (can, cannot) be used as an aid for identifi cation.

48. The pattern of a(n) ______________ and ______________ absorption spectrum suggest a probable identity of a drug.

49. An (infrared, ultraviolet) absorption spectrum provides a unique “fi ngerprint” of a chemical substance.

50. The study of the absorption of light by chemical substances is known as ______________ , and the instrument used to measure and record this absorption spectrum is the ______________ .

51. A mixture’s components can be separated by the technique of ______________ , which separates mixtures on the basis of their distribution between a stationary liquid phase and a moving gas phase.

52. The gas chromatograph, in combination with the ______________ , can separate the components of a drug mixture and then unequivocally identify each substance present in the mixture.

53. The technique of ______________ exposes molecules to a beam of high-energy electrons in order to fragment them.

54. True or False: A mass spectrum is normally considered a specifi c means for identifying a chemical substance. ______________

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APPLICATION AND CRITICAL THINKING

1. An individual who has been using a drug for an extended period of time suddenly fi nds himself unable to secure more of the drug. He acts nervous and irritable and is hyperac- tive. He seems almost desperate to fi nd more of the drug but experiences no sickness, pain, or other outward physical discomfort. Based on his behavior, what drugs might he pos- sibly have been using? Explain your answer.

2. Following are descriptions of behavior that are characteristic among users of certain classes of drugs. For each descrip- tion, indicate the class of drug (narcotics, stimulants, and so on) for which the behavior is most characteristic. For each description, also name at least one drug that produces the described effects.

a) Slurred speech, slow reaction time, impaired judgment, reduced coordination

b) Intense emotional responses, anxiety, altered sensory perceptions

c) Alertness, feelings of strength and confi dence, rapid speech and movement, decreased appetite

d) Drowsiness, intense feeling of well-being, relief from pain

3. Following are descriptions of four hypothetical drugs. According to the Controlled Substances Act, under which drug schedule would each substance be classifi ed?

a) This drug has a high potential for psychological depen- dence, it currently has accepted medical uses in the United States, and the distributor is not required to report to the US Drug Enforcement Administration.

b) This drug has medical use in the United States, is not limited by manufacturing quotas, and may be exported without a permit.

c) This drug must be stored in a vault or safe, requires separate record keeping, and may be distributed with a prescription.

d) This drug may not be imported or exported without a permit, is subject to manufacturing quotas, and cur- rently has no medical use in the United States.

4. A police offi cer stops a motorist who is driving erratically and notices a bag of white powder that he suspects is heroin on the front seat of the car. The offi cer brings the bag to you, a forensic scientist in the local crime lab. Name one screening test that you might perform to determine the presence of heroin. Assuming the powder tests positive for heroin, what should you do next?

5. The fi gure below shows a chromatogram of a known mixture of barbiturates. Based on this fi gure, answer the following questions:

a) What barbiturate detected by the chromatogram had the longest retention time?

b) Which barbiturate had the shortest retention time?

c) What is the approximate retention time of amobarbital?

0 1 2 3 4 5 6 7 8 9 10 11 12

Butabarbital

Amobarbital

Pentobarbital

Secobarbital

Phenobarbital

TIME (MINUTES)(b)

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DRUGS

ENDNOTES

1. Marijuana–A Signal of Misunderstanding. (Washington, DC: US Government Printing Offi ce, 1972), p. 56.

6. When investigating a warehouse for potentially storing illegal drugs, the police collected a variety of drugs. The drugs were tested with presumptive color tests for determining

their possible identity. The test tubes shown in the following fi gure display the positive color tests. Match the drugs on the right with the color tests on the left and name the test.

330

WHAT KILLED NAPOLEON? Napoleon I, emperor of France, was sent into exile on the remote island of St. Helena by the British after his defeat at the Battle of Waterloo in 1815. St. Helena was hot, unsanitary, and rampant with disease. There, Napoleon was confi ned to a large reconstructed agricultural build- ing known as Longwood House. Boredom and unhealthy

living conditions gradually took their toll on Napoleon’s mental and physical state. He began suffering from severe abdomi- nal pains and experienced swelling of the ankles and general weakness of his limbs. From the fall of 1820, Napoleon’s health began to deteriorate rapidly until he died on May 5, 1821. An autopsy concluded the cause of death was stomach cancer.

Because Napoleon died in British captivity, it was inevitable that numerous conspiratorial theories would develop to account for his death. One of the most fascinating inquiries was conducted by a Swedish dentist, Sven Forshufvud, who systematically correlated the clini- cal symptoms of Napoleon’s last days to those of arsenic poisoning. He published a book in Swedish about this case in 1961 For Forshufvud, the key to unlocking the

cause of Napoleon’s death rested with Napoleon’s hair. Forshufvud arranged to have Napoleon’s hair measured for arsenic content by neutron activation analysis and found it consistent with arsenic poisoning. Neverthe- less, the cause of Napoleon’s demise is still a matter for debate and speculation. Other Napoleon hairs collected in 1805 and 1814 have also shown high concentrations of arsenic, giving rise to the speculation that Napoleon was innocently exposed to arsenic over a long period of time. Even hair collected from Napoleon’s three sisters show signifi cant levels of arsenic. Some scientists ques- tion whether Napoleon even had the clinical symptoms associated with arsenic poisoning. In truth, forensic sci- ence may never be able to answer the question, What killed Napoleon?

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Explain how alcohol is absorbed into the bloodstream,

transported throughout the body, and eliminated by oxidation and excretion.

• Understand the process by which alcohol is excreted in the breath via the lungs.

• Understand the concepts of infrared and fuel cell breath- testing devices for alcohol testing.

• Describe commonly employed fi eld sobriety tests to assess alcohol impairment.

• List and contrast laboratory procedures for measuring the concentration of alcohol in the blood.

• Relate the precautions necessary to properly preserve blood in order to analyze its alcohol content.

• Understand the signifi cance of implied-consent laws and the Schmerber v. California case to traffi c enforcement.

• Describe techniques that forensic toxicologists use to isolate and identify drugs and poisons.

• Appreciate the signifi cance of fi nding a drug in human tissues and organs as it relates to assessing impairment.

• Describe how to coordinate the drug recognition expert (DRE) program with a forensic toxicology fi nding.

Forensic

Toxicology

© Archive Images / Alamy © Archive Imagegg s / Alamyyy

From Chapter 12 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

FORENSIC TOXICOLOGY

Role of Forensic Toxicology Because the uncontrolled use of drugs has become a worldwide problem affect- ing all segments of society, the role of the toxicologist has taken on new and added signifi cance. Toxicologists detect and identify drugs and poisons in body fl uids, tissues, and organs. Their services are not only required in such legal insti- tutions as crime laboratories and medical examiners’ offi ces, but they also reach into hospital laboratories—where identifying a drug overdose may represent the difference between life and death—and into various health facilities that monitor the intake of drugs and other toxic substances. Primary examples include per- forming blood tests on children exposed to leaded paints and analyzing the urine of addicts enrolled in methadone maintenance programs.

The role of the forensic toxicologist is limited to matters that pertain to violations of criminal law. However, responsibility for performing toxicologi- cal services in a criminal justice system varies considerably throughout the United States. In systems with a crime laboratory independent of the medical examiner’s offi ce, this responsibility may reside with one or the other, or it may be shared by both. Some systems, however, take advantage of the expertise of government health department laboratories and assign this role to them. Nevertheless, whatever facility handles this work, its caseload will refl ect the prevailing popularity of the drugs that are abused in the community. In most cases, this means that the forensic toxicologist handles numerous requests to determine the presence of alcohol in the body.

All of the statistical and medical evidence available shows that ethyl alcohol—a legal, over-the-counter substance—is the most heavily abused drug in Western countries. Forty percent of all traffi c deaths in the United States— nearly 17,500 fatalities per year—are alcohol related, along with more than two million injuries that require hospital treatment each year. This highway death toll, as well as the untold damage to life, limb, and property, shows the dangerous consequences of alcohol abuse. Because of the prevalence of alco- hol in the toxicologist’s work, we will begin by taking a closer look at how the body processes and responds to alcohol.

Quick Review • Forensic toxicologists detect and identify drugs and poisons in body fl uids,

tissues, and organs in situations that involve violations of criminal laws. • Ethyl alcohol is the most heavily abused drug in Western countries.

Toxicology of Alcohol The subject of the alcohol analysis immediately confronts us with the primary objective of forensic toxicology: to detect and isolate drugs in the body so that their infl uence on human behavior can be determined. Knowing how the body metabolizes alcohol provides the key to understanding its effects on human behavior. This knowledge has also made possible the development of instru- ments that measure the presence and concentration of alcohol in individuals suspected of driving while under its infl uence.

METABOLISM OF ALCOHOL

All chemicals that enter the body are eventually broken down by chemicals within the body and transformed into other chemicals that are easier to elim- inate. This process of transformation, called metabolism , consists of three basic steps: absorption, distribution, and elimination.

toxicologist An individual charged with the responsibility of detecting and identifying the presence of drugs and poisons in body fl uids, tissues, and organs.

metabolism The transformation of a chemical in the body to other chemicals for the purpose of facilitating its elimination from the body.

332

FORENSIC TOXICOLOGY

ABSORPTION AND DISTRIBUTION Alcohol, or ethyl alcohol, is a colorless liquid normally diluted with water and consumed as a beverage. Alcohol appears in the blood within minutes after it has been consumed and slowly increases in concentration while it is being absorbed from the stomach and the small intestine into the bloodstream. During the absorption phase, alcohol slowly enters the body’s bloodstream and is carried to all parts of the body. When the absorption period is completed, the alcohol becomes distributed uni- formly throughout the watery portions of the body—that is, throughout about two-thirds of the body volume. Fat, bones, and hair are low in water content and therefore contain little alcohol, whereas alcohol concentration in the rest of the body is fairly uniform. After absorption is completed, a maximum alco- hol level is reached in the blood, and the postabsorption period begins. Then the alcohol concentration slowly decreases until it reaches zero again.

Many factors determine the rate at which alcohol is absorbed into the bloodstream, including the total time taken to consume the drink, the alcohol content of the beverage, the amount consumed, and the quantity and type of food present in the stomach at the time of drinking. With so many variables, it is diffi cult to predict just how long the absorption process will require. For example, beer is absorbed more slowly than an equivalent concentration of al- cohol in water, apparently because of the carbohydrates in beer. Also, alcohol consumed on an empty stomach is absorbed faster than an equivalent amount of alcohol taken when there is food in the stomach (see Figure 1 ).

ELIMINATION As the alcohol is circulated by the bloodstream, the body be- gins to eliminate it. Alcohol is eliminated through two mechanisms: oxidation and excretion . Nearly all of the alcohol consumed (95 to 98 percent) is even- tually oxidized to carbon dioxide and water. Oxidation takes place almost en- tirely in the liver. There, in the presence of the enzyme alcohol dehydrogenase , the alcohol is converted into acetaldehyde and then to acetic acid. The acetic acid is subsequently oxidized in practically all parts of the body, becoming carbon dioxide and water.

The remaining alcohol is excreted, unchanged, in the breath, urine, and perspiration. Most signifi cant, the amount of alcohol exhaled in the breath is in di- rect proportion to the concentration of alcohol in the blood. This observation has had a tremendous impact on the technology and procedures used for blood- alcohol testing. The development of instruments to reliably measure breath for its alcohol content has made possible the testing of millions of people in a quick, safe, and convenient manner.

The fate of alcohol in the body is therefore rela- tively simple—namely, absorption into the blood- stream, distribution throughout the body’s water, and fi nally, elimination by oxidation and excretion. The elimination, or “burn-off,” rate of alcohol varies in different individuals; 0.015 percent w/v (weight per volume) per hour is the average rate after the absorp- tion process is complete. 1 However, this fi gure is an average that varies by as much as 30 percent among individuals.

BLOOD-ALCOHOL CONCENTRATION Logically, the most obvious measure of intoxication would be the amount of liquor a person has consumed. Unfortu- nately, most arrests are made after the fact, when

absorption The passage of substances such as alcohol across the wall of the stomach and small intestine into the bloodstream.

Immediately after a meal of potatoes

B lo

od a

lc oh

ol —

m g

pe r 1

00 m

L an

d %

w /v

Empty stomach

100 0.10 90

0.09 80

0.08 70

0.07 60

0.06 50 0.05 40

0.04 30

0.03 20

0.02 10

0.01 0

0.00 0 1 2 3

Hours 4 5 6

FIGURE 1 Blood-alcohol concentrations after ingestion of 2 ounces of pure alcohol mixed in 8 ounces of water (equivalent to about 5 ounces of 80-proof vodka). Courtesy US Department of Transportation, Washington, DC

oxidation The combination of oxygen with other substances to produce new products.

excretion The elimination of substances such as alcohol from the body in an unchanged state, typically in breath and urine.

333

FORENSIC TOXICOLOGY

such information is not available to legal authorities; furthermore, even if these data could be collected, numerous related factors, such as body weight and the rate of alcohol’s absorption into the body, are so variable that it would be impossible to prescribe uniform standards that would yield reliable alcohol intoxication levels for all individuals.

Theoretically, for a true determination of the quantity of alcohol impairing an individual’s normal body functions, it would be best to remove a portion of brain tissue and analyze it for alcohol content. For obvious reasons, this cannot be done on living subjects. Consequently, toxicologists concentrate on the blood, which provides the medium for circulating alcohol throughout the body, carrying it to all tissues including the brain. Fortunately, experimental evidence supports this approach and shows blood-alcohol concentration to be directly proportional to the concentration of alcohol in the brain. From the medicolegal point of view, blood-alcohol levels have become the accepted standard for relating alcohol intake to its effect on the body.

The longer the total time required for complete absorption to occur, the lower the peak alcohol concentration in the blood. Depending on a combina- tion of factors, maximum blood-alcohol concentration may not be reached until two or three hours have elapsed from the time of consumption. How- ever, under normal social drinking conditions, it takes anywhere from thirty to ninety minutes from the time of the fi nal drink until the absorption process is completed.

As noted earlier, alcohol becomes concentrated evenly throughout the wa- tery portions of the body. This knowledge can be useful for the toxicologist analyzing a body for the presence of alcohol. If blood is not available, as in some postmortem situations, a medical examiner can select a water-rich or- gan or fl uid—for example, the brain, cerebrospinal fl uid, or vitreous humor—

to test the body’s alcohol content to a reasonable degree of accuracy.

ALCOHOL IN THE

CIRCULATORY SYSTEM

The extent to which an individual may be under the infl uence of alcohol is usually determined by measuring the quantity of alcohol present in the blood system. Normally, this is accomplished in one of two ways: (1) by analyzing the blood for its alcohol content or (2) by measuring the alco- hol content of the breath. In either case, the sig- nifi cance and meaning of the results can better be understood when the movement of alcohol through the circulatory system is studied.

Humans, like all vertebrates, have a closed circulatory system, which consists basically of a heart and numerous arteries, capillaries, and veins. An artery is a blood vessel carrying blood away from the heart, and a vein is a vessel car- rying blood back toward the heart. Capillaries are tiny blood vessels that connect the arter- ies with the veins. The exchange of materials between the blood and the other tissues takes place across the thin walls of the capillaries. A  schematic diagram of the circulatory system is shown in Figure 2 .

Pulmonary artery

Vein

Body tissues

Artery

Lungs

RA LA

RV LV

Pulmonary vein

FIGURE 2 A simplifi ed diagram of the human circulatory system. Vessels shown in red contain oxygenated blood; vessels shown in gray contain de- oxygenated blood.

artery A blood vessel that carries blood away from the heart.

vein A blood vessel that transports blood toward the heart.

capillary A tiny blood vessel that receives blood from arteries and carries it to veins, and across whose walls the exchange of materials between the blood and the tissues takes place.

334

FORENSIC TOXICOLOGY

INGESTION AND DISTRIBUTION Let us now trace the movement of alcohol through the human circulatory system. After alcohol is ingested, it moves down the esophagus into the stomach. About 20 percent of the alcohol is ab- sorbed through the stomach walls into the portal vein of the blood system. The remaining alcohol passes into the blood through the walls of the small intestine. Once in the blood, the alcohol is carried to the liver, where enzymes begin to break it down.

As the blood (still carrying the alcohol) leaves the liver, it moves up to the heart. The blood enters the upper right chamber of the heart, called the right atrium (or auricle), and is forced into the lower right chamber of the heart, known as the right ventricle. Having returned to the heart from its circulation through the tissues, the blood at this time contains very little oxygen and much carbon dioxide. Consequently, the blood must be pumped up to the lungs, through the pulmonary artery, to be replenished with oxygen.

AERATION In the lungs, the respiratory system bridges with the circulatory system so that oxygen can enter the blood and carbon dioxide can leave it. As shown in Figure 3 , the pulmonary artery branches into capillaries lying close to tiny pear-shaped sacs called alveoli . The lungs contain about 250  million alveoli, all located at the ends of the bronchial tubes. The bronchial tubes con- nect to the windpipe (trachea), which leads up to the mouth and nose (see Fig- ure 4 ). At the surface of the alveolar sacs, blood fl owing through the capillaries comes into contact with fresh oxygenated air in the sacs.

A rapid exchange now takes place between the fresh air in the sacs and the spent air in the blood. Oxygen passes through the walls of the alveoli into the blood while carbon dioxide is discharged from the blood into the air. If, during this exchange, alcohol or any other volatile substance is in the blood, it too will

Pulmonary artery

Pulmonary vein

Bronchial tube

Carbon dioxide Alveolar sac

Carbon dioxide

Oxygen Alveolar sac

Oxygen

FIGURE 3 Gas exchange in the lungs. Blood fl ows from the pulmonary artery into vessels that lie close to the walls of the alveoli. Here the blood gives up its carbon dioxide and absorbs oxygen. The oxygenated blood leaves the lungs via the pulmonary vein and returns to the heart.

alveoli Small sacs in the lungs through whose walls air and other vapors are exchanged between the breath and the blood.

335

FORENSIC TOXICOLOGY

pass into the alveoli. During breathing, the car- bon dioxide and alcohol are expelled through the nose and mouth, and the alveoli are replen- ished with fresh oxygenated air breathed into the lungs, allowing the process to begin all over again.

The temperature at which the breath leaves the mouth is normally 34°C. At this tem- perature, the ratio of alcohol in the blood to alcohol in alveolar air is approximately 2,100 to 1. In other words, 1 milliliter of blood con- tains nearly the same amount of alcohol as 2,100 milliliters of alveolar breath.

RECIRCULATION AND ABSORPTION Now let’s return to the circulating blood. After emerging from the lungs, the oxygenated blood is rushed back to the upper left chamber of the heart (left atrium) by the pulmonary vein. When the left atrium contracts, it forces the blood through a valve into the left ventricle, which is the lower left chamber of the heart. The left ventricle then pumps the freshly oxygenated blood into the arteries, which carry the blood to all parts of the body. Each of these arteries, in turn, branches into smaller arteries, which eventually connect with the numerous tiny capillaries embedded in the tissues. Here the alcohol moves out of the blood and into the tissues. The blood then runs from the capillaries into tiny veins that fuse to form larger veins. These veins eventually lead back to the heart to complete the circuit.

During absorption, the concentration of alcohol in the arterial blood is considerably higher than the concentration of alcohol in the venous blood. One typical study revealed a subject’s arterial blood-alcohol level to be 41 per- cent higher than the venous level thirty minutes after the subject’s last drink. 2 This difference is thought to exist because of the rapid diffusion of alcohol into the body tissues from venous blood during the early phases of absorption. Be- cause the administration of a blood test requires drawing venous blood from the arm, this test is clearly to the advantage of a subject who may still be in the absorption stage. However, once absorption is complete, the alcohol becomes equally distributed throughout the blood system.

Quick Review • Alcohol appears in the blood within minutes after it has been taken by

mouth. It slowly increases in concentration while it is being absorbed from the stomach and the small intestine into the bloodstream.

• When all the alcohol has been absorbed, a maximum alcohol level is reached in the blood, and the postabsorption period begins. During postabsorption, the alcohol concentration slowly decreases until a zero level is reached.

• Elimination of alcohol throughout the body is accomplished through oxidation and excretion. Oxidation takes place almost entirely in the liver, whereas alcohol is excreted unchanged in the breath, urine, and perspiration.

• Breath-testing devices operate on the principle that the ratio between the con- centration of alcohol in alveolar breath and its concentration in blood is fi xed.

Nasal cavity

Larynx

Trachea Esophagus

Bronchial tube

Alveolar sac

FIGURE 4 The respiratory system. The trachea connects the nose and mouth to the bronchial tubes. The bronchial tubes divide into numerous branches that terminate in the alveoli in the lungs.

336

FORENSIC TOXICOLOGY

Testing for Intoxication From a practical point of view, drawing blood from veins of motorists sus- pected of being under the infl uence of alcohol is simply not convenient. The need to transport each suspect to a location where a medically qualifi ed per- son can draw blood would be costly and time consuming, considering the hundreds of suspects that the average police department must test every year. The methods used must be designed to test hundreds of thousands of motorists annually, without causing them undue physical harm or unreason- able inconvenience, and provide a reliable diagnosis that can be supported and defended within the framework of the legal system. This means that toxicologists have had to devise rapid and specifi c procedures for measur- ing a driver’s degree of alcohol intoxication that can be easily administered in the fi eld.

BREATH TESTING FOR ALCOHOL

The most widespread method for rapidly determining alcohol intoxication is breath testing. A breath tester is simply a device for collecting and measuring the alcohol content of alveolar breath. As we saw earlier, alcohol is expelled, unchanged, in the breath of a person who has been drinking. A breath test measures the alcohol concentration in the pulmonary artery by measuring its concentration in alveolar breath. Thus, breath analysis provides an easily obtainable specimen along with a rapid and accurate result.

Breath-test results obtained during the absorption phase may be higher than results obtained from a simultaneous analysis of venous blood. However, the former are more refl ective of the concentration of alcohol reaching the brain and therefore more accurately refl ect the effects of alcohol on the sub- ject. Again, once absorption is complete, the difference between a blood test and a breath test should be minimal.

BREATH-TEST INSTRUMENTS The fi rst widely used instrument for measuring the alcohol content of alveolar breath was the Breathalyzer , developed in 1954 by R. F. Borkenstein, who was a captain in the Indiana State Police. Starting in the 1970s, the Breathalyzer was phased out and replaced by other instru- ments. Like the Breathalyzer, they assume that the ratio of alcohol in the blood to alcohol in alveolar breath is 2,100 to 1 at a mouth temperature of 34°C. Unlike the Breathalyzer, modern breath testers are free of chemicals. These devices include infrared light–absorption devices (described in the Closer Analysis feature) and fuel cell detectors .

Infrared and fuel-cell-based breath testers are microprocessor controlled, so all an operator has to do is to press a start button; the instrument auto- matically moves through a sequence of steps and produces a readout of the subject’s test results. These instruments also perform self-diagnostic tests to ascertain whether they are in proper operating condition.

CONSIDERATIONS IN BREATH TESTING An important feature of these instru- ments is that they can be connected to an external alcohol standard or simu- lator in the form of either a liquid or a gas. The liquid simulator comprises a known concentration of alcohol in water. It is heated to a controlled tempera- ture and the vapor formed above the liquid is pumped into the instrument. Dry-gas standards typically consist of a known concentration of alcohol mixed with an inert gas and compressed in cylinders. The external standard is auto- matically sampled by the breath-test instrument before and/or after the sub- ject’s breath sample is taken and recorded. Thus the operator can check the accuracy of the instrument against the known alcohol standard.

fuel cell detector A detector in which a chemical reaction involving alcohol produces electricity.

337

FORENSIC TOXICOLOGY

CLOSER ANALYSIS INFRARED LIGHT ABSORPTION

In principle, infrared instruments operate no differently than spectro- photometers . An evidential testing instrument that incorporates the principle of infrared light absorption is shown in Figure 1 . Any alco- hol present in the subject’s breath fl ows into the instrument’s breath chamber. As shown in Figure 2 , a beam of infrared light is aimed through the chamber. A fi lter is used to select a wavelength of in- frared light at which alcohol will absorb. As the infrared light passes through the chamber, it interacts with the alcohol and causes the light to decrease in intensity. The decrease in light intensity is mea- sured by a photoelectric detector that gives a signal proportional to

the concentration of alcohol present in the breath sample. This infor- mation is processed by an electronic microprocessor, and the percent blood-alcohol concentration is displayed on a digital readout. Also, the blood-alcohol level is printed on a card to produce a permanent record of the test result. Most infrared breath testers aim a second infrared beam into the same chamber to check for acetone or other chemical interferences on the breath. If the instrument detects differ- ences in the relative response of the two infrared beams that does not conform to ethyl alcohol, the operator is immediately informed of the presence of an “interferant.”

FIGURE 1 An infrared breath-testing instrument—the BAC Data Master. Courtesy National Patent Analytical Systems, Inc., Mansfi eld, OH 44901

The key to the accuracy of a breath-testing device is to ensure that the unit captures the alcohol in the alveolar (i.e., deep-lung) breath of the subject. This is typically accomplished by programming the unit to accept no less than 1.1 to 1.5 liters of breath from the subject. Also, the subject must blow for a minimum time (such as 6 seconds) with a minimum breath fl ow rate (such as 3 liters per minute).

The breath-test instruments just described feature a slope detector , which ensures that the breath sample is alveolar, or deep-lung, breath. As the subject blows into the instrument, the breath-alcohol concentration is continuously monitored. The instrument accepts a breath sample only when consecutive measurements fall within a predetermined rate of change. This approach en- sures that the sample measurement is deep-lung breath and closely relates to the true blood-alcohol concentration of the subject being tested.

A breath-test operator must take other steps to ensure that the breath-test result truly refl ects the actual blood-alcohol concentration within the subject. A major consideration is to avoid measuring “mouth alcohol” resulting from regurgitation, belching, or recent intake of an alcoholic beverage. Also, recent gargling with an alcohol-containing mouthwash can lead to the presence of mouth alcohol. As a result, the alcohol concentration detected in the exhaled breath is higher than the concentration in the alveolar breath. To avoid this possibility, the operator must not allow the subject to take any foreign mate- rial into his or her mouth for at least fi fteen minutes before the breath test.

338

DetectorInfrared radiation source

Sample chamber Filter

Breath inlet

Breath outlet

Breath flows into chamber

Infrared radiation source

Sample chamber

Breath inlet

Breath outlet

Detector

Infrared light beamed through chamber. Alcohol in breath absorbs some infrared light.

Infrared radiation source

Sample chamber Filter selects wavelength of IR light at which alcohol absorbs

Breath inlet

Breath outlet

Detector

Infrared radiation source

Sample chamber

Breath inlet

Breath outlet

Detector converts infrared light to an electrical signal proportional to the alcohol content in breath.

Infrared radiation source

Sample chamber

Breath inlet

Breath outlet

Detector Breath-alcohol content is converted into a blood-alcohol concentration and displayed on a digital readout.

FIGURE 2 A schematic diagram of an infrared breath-testing instrument.

339

FORENSIC TOXICOLOGY

CLOSER ANALYSIS THE FUEL CELL

A fuel cell converts energy arising from a chemical reaction into electrochemical energy. A typical fuel cell consists of two plati- num electrodes separated by an acid- or base-containing porous membrane. A platinum wire connects the electrodes and allows a current to fl ow between them. In the alcohol fuel cell, one of the electrodes is positioned to come into contact with a subject’s breath sample. If alcohol is present in the breath, a reaction at the electrode’s surface converts the alcohol to acetic acid. One by-product of this conversion is free electrons, which fl ow through the connecting wire to the opposite electrode, where they interact with atmospheric oxygen to form water (see fi gure). The fuel cell also requires the migration of hydrogen ions across the acidic po- rous membrane to complete the circuit. The strength of the current fl ow between the two electrodes is proportional to the concentra- tion of alcohol in the breath.

Breath

Acetic acid

Oxygen

Alcohol H2O Outlet

e– e

– e– e – e

– e –

Porous membrane

A detector in which chemical reactions are used to produce electricity.

Likewise, the subject should be observed not to have belched or regurgitated during this period. Mouth alcohol has been shown to dissipate after fi fteen to twenty minutes from its inception.

Measurement of independent breath samples taken within a few minutes of each other is another extremely important check of the integrity of the breath test. Acceptable agreement between the two tests taken minutes apart signifi cantly reduces the possibility of errors caused by the operator, mouth alcohol, instrument component failures, and spurious electric signals.

FIELD SOBRIETY TESTING

A police offi cer who suspects that an individual is under the infl uence of alco- hol usually conducts a series of preliminary tests before ordering the suspect to submit to an evidential breath or blood test. These preliminary, or fi eld, sobriety tests are normally performed to ascertain the degree of the suspect’s physical impairment and whether an evidential test is justifi ed.

Field sobriety tests usually consist of a series of psychophysical tests and a preliminary breath test (if such devices are authorized and available for use). A portable, handheld, roadside breath tester is shown in Figure 5 . This device, about the size of a pack of cigarettes, weighs 5 ounces and uses a fuel cell to measure the alcohol content of a breath sample. The fuel cell absorbs the alcohol from the breath sample, oxidizes it, and produces an electrical current propor- tional to the breath-alcohol content. This instrument can typically be used for three to fi ve years before the fuel cell needs to be replaced. Breath-test results obtained with devices such as those shown in Figure 5 must be considered pre- liminary and nonevidential. They should only establish probable cause for re- quiring an individual to submit to a more thorough breath or blood test.

Horizontal-gaze nystagmus, “walk and turn,” and the one-leg stand con- stitute a series of reliable and effective psychophysical tests. Horizontal-gaze

340

FORENSIC TOXICOLOGY

FIGURE 5 The Alco-Sensor IV. Courtesy Intoximeters, Inc., St. Louis, MO, www.intox.com

nystagmus is an involuntary jerking of the eye as it moves to the side. A person experiencing nystagmus is usually unaware that the jerking is happening and is unable to stop or control it. The subject being tested is asked to follow a penlight or some other object with his or her eye as far to the side as the eye can go. The more intoxicated the person is, the less the eye has to move toward the side before jerking or nystagmus begins. Usually, when a person’s blood-alcohol concentration is in the range of 0.10 percent, the jerking begins before the eyeball has moved 45 degrees to the side (see Figure 6 ). Higher blood-alcohol concentra- tion causes jerking at smaller angles. Also, if the suspect has taken a drug that also causes nystagmus (such as phencyclidine, barbiturates, and other depressants), the nystagmus-onset angle may occur much earlier than would be expected from alcohol alone.

Walk and turn and the one-leg stand are divided-attention tasks, test- ing the subject’s ability to comprehend and execute two or more simple instructions at one time. The ability to understand and simultaneously carry out more than two instructions is signifi cantly affected by increasing blood-alcohol levels. Walk and turn requires the suspect to maintain balance while standing heel-to-toe and at the same time listening to and comprehend- ing the test instructions. During the walking stage, the suspect must walk a straight line, touching heel-to-toe for nine steps, then turn around on the line and repeat the process. The one-leg stand requires the suspect to maintain bal- ance while standing with heels together listening to the instructions. During the balancing stage, the suspect must stand on one foot while holding the other foot several inches off the ground for 30 seconds; simultaneously, the suspect must count out loud during the 30-second time period.

Quick Review • Modern breath testers are free of chemicals. They include infrared light

absorption devices and fuel cell detectors. • The key to the accuracy of a breath-testing device is to ensure that the unit

captures the alcohol in the alveolar (deep-lung) breath of the subject. • Many breath testers collect a set volume of breath and expose it to infrared

light. The instrument measures the concentration of alcohol in the col- lected breath sample by measuring the degree of interaction between the light and the alcohol present.

Eye looking straight ahead

45°

FIGURE 6 When a person’s blood- alcohol level is in the vicinity of 0.10 percent, jerking of the eye during the horizontal-gaze nys- tagmus test will begin before the eyeball has moved 45 degrees to the side.

341

FORENSIC TOXICOLOGY

• Law enforcement offi cers use fi eld sobriety tests to estimate a motorist’s degree of physical impairment from alcohol and to determine whether an evidential test for alcohol is justifi ed.

• The horizontal-gaze nystagmus test, the walk and turn, and the one-leg stand are all considered reliable and effective psychophysical tests for alcohol impairment.

Analysis of Blood for Alcohol Gas chromatography is the approach most widely used by forensic toxicolo- gists for determining alcohol levels in blood. Under proper gas chromato- graphic conditions, alcohol can be separated from other volatile substances in the blood. By comparing the resultant alcohol peak area to ones obtained from known blood-alcohol standards, the investigator can calculate the alco- hol level with a high degree of accuracy (see Figure 7 ).

Another procedure for alcohol analysis involves the oxidation of alcohol to acetaldehyde. This reaction is carried out in the presence of the enzyme alcohol dehydrogenase and the coenzyme nicotin-amide-adenine dinucleotide (NAD). As the oxidation proceeds, NAD is converted into another chemical species, NADH. The extent of this conversion is measured by a spectrophotometer and is related to alcohol concentration. This approach to blood- alcohol testing is normally associated with instruments used in clinical or hospital settings. Instead, forensic laboratories normally use gas chromatography for determin- ing blood-alcohol content.

COLLECTION AND PRESERVATION

OF BLOOD

Blood must always be drawn under medically acceptable conditions by a qualifi ed individual. A nonalcoholic disinfec- tant should be applied before the suspect’s skin is penetrated with a sterile needle or lancet. It is important to eliminate any possibility that an alcoholic disinfectant could inadvertently contribute to a falsely high blood-alcohol result. Nonalco- holic disinfectants such as aqueous benzalkonium chloride (Zepiran), aqueous mercuric chloride, or povidone-iodine (Betadine) are recommended for this purpose.

Once blood is removed from an individual, it is best pre- served sealed in an airtight container after adding an antico- agulant and a preservative. The blood should be stored in a refrigerator until delivery to the toxicology laboratory. The addition of an anticoagulant , such as EDTA or potassium oxalate, prevents clotting; a preservative , such as sodium fl uoride, inhibits the growth of microorganisms capable of destroying alcohol.

One study performed to determine the stability of alco- hol in blood removed from living individuals found that the most signifi cant factors affecting alcohol’s stability in blood are storage temperature, the presence of a preservative, and the length of storage. 3 Not a single blood specimen examined showed an increase in alcohol level with time. Failure to keep the blood refrigerated or to add sodium fl uoride resulted in a substantial decline in alcohol concentration. Longer stor- age times also reduced blood-alcohol levels. Hence, failure to

Time (minutes) 0 3 2 1

Ethanol

FIGURE 7 A gas chromatogram showing ethyl alcohol (ethanol) in whole blood. Courtesy Varian Inc., Palo Alto, CA

anticoagulant A substance that prevents coagulation or clotting of the blood.

preservative A substance that stops the growth of microorganisms in blood.

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adhere to any of the proper preservation requirements for blood works to the benefi t of the suspect and to the detriment of society.

The collection of postmortem blood samples for alcohol-level determina- tions requires added precautions. Ethyl alcohol may be generated in the body of a deceased individual as a result of bacterial action. Therefore, it is best to collect a number of blood samples from different body sites. For example, blood may be removed from the heart and from the femoral vein (in the leg) and cubital vein (in the arm). Each sample should be placed in a clean, airtight container containing an anticoagulant and sodium fl uoride preservative and should be refrigerated. Blood-alcohol levels can be attributed solely to alco- hol consumption if they are nearly similar in all blood samples collected from the same person. As an alternative to blood collection, the collection of vitre- ous humor and urine is recommended. Vitreous humor and urine usually do not experience any signifi cant postmortem ethyl alcohol production.

Quick Review • Gas chromatography is the most widely used approach for determining

blood-alcohol levels in forensic laboratories. • An anticoagulant should be added to a blood sample to prevent clotting;

a preservative should be added to inhibit the growth of microorganisms capable of destroying alcohol.

Alcohol and the Law Constitutionally, every state in the United States must establish and administer statutes regulating the operation of motor vehicles. Although such an arrange- ment might encourage diverse laws defi ning permissible blood-alcohol levels, this has not been the case. Since the 1930s, both the American Medical Association and the National Safety Council have exerted considerable infl uence in persuading the states to establish uniform and reasonable blood-alcohol standards.

BLOOD-ALCOHOL LAWS

The American Medical Association and the National Safety Council initially recommended that a person with a blood-alcohol concentration in excess of 0.15 percent w/v was to be considered under the infl uence of alcohol. 4 However, subsequent experimental studies showed a clear correlation between drinking and driving impairment at blood-alcohol levels much below 0.15 percent w/v. These fi ndings eventually led to a lowering of the blood-concentration stan- dard for intoxication from 0.15 percent w/v to its current 0.08 percent w/v.

In 1992, the US Department of Transportation (DOT) recommended that states adopt 0.08 percent blood-alcohol concentration as the legal measure of drunk driving. This recommendation was enacted into federal law in 2000. All fi fty states have now established per se laws , meaning that any individual meeting or exceeding a defi ned blood-alcohol level (usually 0.08 percent) shall be deemed intoxicated. No other proof of alcohol impairment is necessary. Starting in 2003, states that had not adopted the 0.08 percent per se level stood to lose part of their federal funds for highway construction. The 0.08 percent level applies only to noncommercial drivers, as the federal government has set the maximum allowable blood-alcohol concentration for commercial truck and bus drivers at 0.04 percent.

Several other Western countries have also set 0.08 percent w/v as the blood-alcohol level above which it is an offense to drive a motor vehicle, in- cluding Canada, Italy, Switzerland, and the United Kingdom. Finland, France,

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Germany, Ireland, Japan, the Netherlands, and Norway have a 0.05 percent limit, as do the Australian states. Sweden has lowered its blood- alcohol concentration limit to 0.02 percent.

As shown in Figure 8 , a driver with a blood- alcohol level of 0.08 percent is about four times as likely to become involved in an automobile accident than a sober individual. At the 0.15 per- cent level, the chances of an automobile accident are twenty-fi ve times higher than those for a so- ber driver. To estimate the relationship of blood- alcohol levels to body weight and the quantity of 80-proof liquor consumed, refer to Figure 9 .

CONSTITUTIONAL ISSUES

The Fifth Amendment to the US Constitution guarantees all citizens protection against self- incrimination —that is, against being forced to make an admission that would prove one’s own guilt in a legal matter. Because consenting to a breath test for alcohol might be considered a form of self-incrimination, the National Highway

About 25 times as much as normal at 0.15%

.00 .04 .08 .12 .16 .20 Blood-alcohol concentration

About 4 times as much as normal at 0.08%

Re la

tiv e

ch an

ce s

of a

c ra

sh

1

5

10

15

20

25

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FIGURE 8 A diagram of increased driving risk in relation to blood-alcohol concentration. Courtesy US Department of Transportation, Washington, DC

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“Full stomach” “Empty stomach”

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How to Tell What Your Blood Alcohol Level Is after Drinking

8

5

FIGURE 9 To use this diagram, lay a straight edge across your weight and the number of ounces of liquor you’ve consumed on an empty or full stomach. The point where the edge hits the right-hand column is your maximum blood-alcohol level. The rate of elimination of alcohol from the bloodstream is approximately 0.015 percent per hour. Therefore, to calculate your actual blood-alcohol level, subtract 0.015 from the num- ber indicated in the right-hand column for each hour from the start of drinking.

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Traffi c Safety Administration recommended an implied-consent law to pre- vent a person from refusing to take a test on those constitutional grounds. This law states that the operator of a motor vehicle on a public highway must either consent to a test for alcohol intoxication, if requested, or lose his or her license for some designated period—usually six months to one year.

The leading case relating to the constitutionality of collecting a blood specimen for alcohol testing, as well as obtaining other types of physical evi- dence from a suspect without consent, is Schmerber v. California . 5 While be- ing treated at a Los Angeles hospital for injuries sustained in an automobile collision, Armando Schmerber was arrested for driving under the infl uence of alcohol. Despite Schmerber’s objections, a physician took a blood sample from him at the direction of the police department. Schmerber was convicted of driving while intoxicated, and he subsequently appealed the decision. The case eventually reached the US Supreme Court, where Schmerber argued that his privilege against self-incrimination had been violated by the introduction of the results of the blood test at his trial. The Court ruled against him, reasoning that the Fifth Amendment prohibits only compelling a suspect to give testimo- nial evidence that may prove to be self-incriminating; being compelled to fur- nish physical evidence, such as fi ngerprints, photographs, measurements, and blood samples, the Court ruled, was not protected by the Fifth Amendment.

The Court also addressed the question of whether the police violated Schmerber’s Fourth Amendment protection against unreasonable search and seizure by taking a blood specimen from him without a search warrant. The Court upheld the constitutionality of the blood removal, reasoning that in this case the police were confronted with an emergency situation. By the time po- lice offi cials would have been able to obtain a warrant, Schmerber’s blood- alcohol levels would have declined signifi cantly as a result of natural body elimination processes. In effect, the evidence would have been destroyed. The Court also emphasized that the blood specimen was taken in a medically accepted manner and without unreasonable force. This opinion in no way condones warrantless taking of blood for alcohol or drug testing under all cir- cumstances. The reasonableness of actions a police offi cer may take to compel an individual to yield evidence can be judged only on a case-by-case basis.

Quick Review • The current legal measure of drunk driving in the United States is a blood-

alcohol concentration of 0.08 percent, or 0.08 grams of alcohol per 100 mil- liliters of blood.

• The implied-consent law states that the operator of a motor vehicle on a public highway must either consent to a test for alcohol intoxication, if requested, or lose his or her license for some designated period—usually six months to one year.

Role of the Toxicologist Once the forensic toxicologist ventures beyond the analysis of alcohol, he or she encounters an encyclopedic maze of drugs and poisons. Even a cursory discussion of the problems and handicaps imposed on toxicologists is enough to engender an appreciation for their accomplishments and ingenuity.

CHALLENGES FACING THE TOXICOLOGIST

The toxicologist is presented with body fl uids and/or organs and asked to ex- amine them for drugs and poisons. When he or she is fortunate, which is not often, some clue about the type of toxic substance present may develop from

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the victim’s symptoms, a postmortem pathological examination, an examina- tion of the victim’s personal effects, or the nearby presence of empty drug containers or household chemicals. Without such supportive information, the toxicologist must use general screening procedures with the hope of narrow- ing thousands of possibilities to one.

If this task does not seem monumental, consider that the toxicologist is not dealing with drugs at the concentration levels found in powders and pills. By the time a drug specimen reaches the toxicology laboratory, it has been dis- sipated and distributed throughout the body. The drug analyst may have gram or milligram quantities of material to work with, but the toxicologist must be satisfi ed with amounts in nanograms or, at best, micrograms, acquired only after being carefully extracted from body fl uids and organs.

Furthermore, the body is an active chemistry laboratory, and no one can appreciate this observation more than a toxicologist. Few substances enter and completely leave the body in the same chemical state. The drug that is in- jected is not always the substance extracted from the body tissues. Therefore, a thorough understanding of how the body alters or metabolizes the chemical structure of a drug is essential in detecting its presence.

It would, for example, be futile and frustrating to search exhaustively for heroin in the human body. This drug is almost immediately metabolized to morphine on entering the bloodstream. Even with this information, the search may still prove impossible unless the examiner also knows that only a small percentage of morphine is excreted unchanged in urine. For the most part, morphine becomes chemically bonded to body carbohydrates before being eliminated in urine. Thus, successful detection of morphine requires that its extraction be planned in accordance with a knowledge of its chemical fate in the body.

Another example of why a toxicologist needs to know how different drugs metabolize in the body is provided by the investigation of the death of Anna Nicole Smith. In her case, the sedative chloral hydrate was a major contribu- tor to her death, but its presence was confi rmed by detecting its active me- tabolite, trichloroethanol (see the Case File).

Last, when and if the toxicologist has surmounted all of these obstacles and has fi nally detected, identifi ed, and quantitated a drug or poison, he or she must assess the substance’s toxicity. Fortunately, there is published informa- tion relating to the toxic levels of most drugs. However, even when such data are available, their interpretation must assume that the victim’s physiological behavior agrees with that of subjects of previous studies. Such an assumption may not be entirely valid without knowing the subject’s case history. No expe- rienced toxicologist would be surprised to fi nd an individual tolerating a toxic level of a drug that would have killed most other people. COLLECTION AND PRESERVATION

OF TOXICOLOGICAL EVIDENCE

The toxicologist’s capabilities depend directly on input from the attending physician, medical examiner, and police investigator. It is a tribute to forensic toxicologists, who often must labor under conditions that do not afford such cooperation, that they can achieve the high level of profi ciency that they do.

Generally, when questions about drug use involve a deceased person, the medical examiner decides what biological specimens must be shipped to the toxicology laboratory for analysis. However, a living person suspected of be- ing under the infl uence of a drug presents a completely different problem, and few options are available. In this case, an entire urine void (i.e., urine sample) is collected and submitted for toxicological analysis. Preferably, two consecu- tive voids should be collected in separate specimen containers.

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CASEFILES CELEBRITY TOXICOLOGY:

MICHAEL JACKSON—THE DEMISE OF A SUPERSTAR

A call to 911 had the desperate tone of urgency. The voice of a young man implored an ambulance to hurry to the home of pop star Michael Jackson. The unconscious performer was in cardiac arrest and was not responding to CPR. The 50-year-old Jackson was pro- nounced dead on arrival at a regional medical center. When the initial autopsy results revealed no signs of foul play, rumors immediately began to swirl around a drug-related death. News media coverage showed investigators carrying bags full of medical supplies out of the Jackson residence. Therefore, it came as no surprise when the forensic toxicology report accompanying Jackson’s autopsy showed that the entertainer had died of a drug overdose.

Apparently, Jackson had become accustomed to receiving sedatives to help him sleep. On the morning of his death, his physician stated that he administered valium to Mr. Jackson. Further, at 2 a.m., he adminis- tered the sedative lorazepam, and at 3 a.m. the physician administered another sedative, midazolam. Those drugs were administered again at 5 a.m. and 7:30 a.m., but Mr. Jackson still was unable to sleep. Finally, at about 10:40 a.m., Jackson’s doctor gave him 25 milligrams of propofol, at which point Mr. Jackson went to sleep. Propofol is a powerful sedative that is principally used for the maintenance of surgical anesthesia. All of the drugs administered to Jackson were sedatives that act in concert to depress the activities of the central nervous system, so it comes as no surprise that this drug cocktail resulted in cardiac arrest and death.

Michael Jackson Justin Sullivan/Pool\AP Wide World Photos

When a licensed physician or registered nurse is available, a sample of blood should also be collected. The amount of blood taken depends on the type of examination to be conducted. Comprehensive toxicological tests for drugs and poisons can conveniently be carried out on a minimum of 10 milliliters of blood. A determination solely for the presence of alcohol will require much less—approximately 5 milliliters of blood. However, many therapeutic drugs, such as tranquilizers and barbiturates, taken in combination with a small, non- intoxicating amount of alcohol, produce behavioral patterns resembling alco- hol intoxication. For this reason, the toxicologist must be given enough blood to perform a comprehensive analysis for drugs in cases in which only low alcohol concentrations are discovered.

TECHNIQUES USED IN TOXICOLOGY

For the toxicologist, the upsurge in drug use and abuse has meant that the overwhelming majority of fatal and nonfatal toxic agents are drugs. Not sur- prisingly, a relatively small number of drugs—compose nearly all the toxic agents encountered. Of these, alcohol, marijuana, and cocaine account for at least 90 percent of the drugs encountered by toxicologists in a typical toxicol- ogy laboratory.

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CASEFILES ACCIDENTAL OVERDOSE:

THE TRAGEDY OF ANNA NICOLE SMITH

Rumors exploded in the media when former model, Playboy play- mate, reality television star, and favorite tabloid subject Anna Nicole Smith was found unconscious at age 39 in her hotel room at the Seminole Hard Rock Hotel & Casino in Hollywood, Florida. She was taken to Memorial Legal Hospital, where she was declared dead. Postmortem analysis of Smith’s blood revealed an array of prescribed medications. Most pronounced was a toxic level of a metabolite of the sedative chloral hydrate. Some of the contents of the toxicology report from Smith’s autopsy are shown here.

Although many of the drugs present were detected at levels consistent with typical doses of the prescribed medications, it was their presence in combination with chloral hydrate that exacer- bated the toxic level of chloral hydrate. The lethal combination of these prescription drugs caused failure of both her circulatory and respiratory systems and resulted in her death. The investigators de- termined that the overdose of chloral hydrate and other drugs was accidental and not a suicide. This was because of the nonexcessive levels of most of the prescription medications and the discovery of a signifi cant amount of chloral hydrate still remaining in its origi- nal container; had she intended to kill herself, she probably would have ingested it all. Anna Nicole Smith was a victim of accidental overmedication.

Anna Nicole Smith Manuel Balce Ceneta / PA Photos\Landov Media

ACIDS AND BASES Like the drug analyst, the toxicologist must devise an ana- lytical scheme to detect, isolate, and identify a toxic substance. The fi rst chore is to remove and isolate drugs and other toxic agents from the biological ma- terials submitted as evidence. Because drugs constitute a large portion of the toxic materials found, a good deal of effort must be devoted to their extraction and detection. So many different procedures are used that a useful descrip- tion of them would be too detailed for this text. We can best understand the underlying principle of drug extraction by observing that many drugs fall into the categories of acids and bases .

By controlling the acidity or basicity (i.e., pH ) of a water solution into which blood, urine, or tissues are dissolved, the toxicologist can control the type of drug that is recovered. For example, acidic drugs are easily extracted from an acidifi ed water solution (i.e., with a pH of less than 7) with organic solvents such as chloroform. Similarly, basic drugs are readily removed from a basic water solution (i.e., with a pH of greater than 7) with organic solvents. This simple approach gives the toxicologist a general technique for extracting and

acid A compound capable of donating a hydrogen ion (H�) to another compound.

base A compound capable of accepting a hydrogen ion (H�).

pH A symbol used to express the basicity or acidity of a substance. A pH of 7 is neutral; lower values are acidic, and higher values are basic.

FINAL PATHOLOGICAL DIAGNOSES

I. ACUTE COMBINED DRUG INTOXICATION

A. Toxic/legal drug: Chloral Hydrate (Noctec)

1. Trichloroethanol (TCE) 75 mg/L (active metabolite)

2. Trichloroacetic acid (TCA) 85 mg/L (inactive metabolite)

B. Therapeutic drugs:

1. Diphenhydramine (Benadryl) 0.11 mg/L

2. Clonazepam (Klonopin) 0.04 mg/L

3. Diazepam (Valium) 0.21 mg/L

4. Nordiazepam (metabolite) 0.38 mg/L

5. Temazepam (metabolite) 0.09 mg/L

6. Oxazepam 0.09 mg/L

7. Lorazepam 0.022 mg/L

C. Other non-contributory drugs present (atropine, topiramate, ciprofl oxacin, acetaminophen)

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categorizing drugs. Some of the more commonly encountered drugs may be classifi ed as follows:

Acid Drugs Basic Drugs

Barbiturates Phencyclidine

Acetylsalicylic acid (aspirin) Methadone

  Amphetamines

  Cocaine

SCREENING AND CONFIRMATION Once the specimen has been extracted and divided into acidic and basic fractions, the toxicologist can identify the drugs present. The strategy for identifying abused drugs entails a two-step approach: screening and confi rmation (see Figure 10 ). A screening test normally gives quick insight into the likeli- hood that a specimen contains a drug substance. This test allows a toxi- cologist to examine a large number of specimens within a short period of time for a wide range of drugs. Any positive results from a screening test are tentative at best and must be verifi ed with a confi rmation test.

Screening Tests. The three most widely used screening tests are thin- layer chromatography (TLC), gas chromatography (GC), and immuno- assay. The third technique, immunoassay, has proved to be a useful screening tool in toxicology laboratories. Its principles are very differ- ent from any of the analytical techniques we have discussed so far. Basically, immunoassay is based on specifi c drug antibody reactions. The primary ad- vantage of immunoassay is its ability to detect small concentrations of drugs in body fl uids and organs. In fact, this technique provides the best approach for detecting the low drug levels normally associated with smoking marijuana.

Confi rmation Tests. A positive screening test may be due to a substance’s close chemical structure to an abused drug. For this reason, the toxicologist must follow up any positive screening test with a confi rmation test. Because of the potential legal impact of the results of a drug fi nding on an individual, only the most conclusive confi rmation procedures should be used.

Gas chromatography/mass spectrometry is generally accepted as the con- fi rmation test of choice. The combination of gas chromatography and mass spectrometry provides a one-step confi rmation test of unequaled sensitivity and specifi city. Figure 11 illustrates the process. After being introduced to the

Acidic Drugs

Sample

SCREENING TEST Immunoassay

Gas chromatography Thin-layer chromatography

CONFIRMATION TEST Gas chromatography/mass spectrometry

Basic Drugs

Extraction at appropriate pH

FIGURE 10 Biological fl uids and tissues are extracted for acidic and basic drugs by controlling the pH of a water solution in which they are dissolved. Once this is ac- complished, the toxicologist analyzes for drugs by using screening and confi rmation test procedures.

D

C

B

A

A B

C

D

Chromatogram Spectra

Gas chromatograph Mass

spectrometer

FIGURE 11 The combination of the gas chromatograph and the mass spectrometer enables forensic toxicologists to separate the components of a drug mixture and enables the specifi c identifi cation of a drug substance.

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gas chromatograph, the sample is separated into its components. When the separated sample component leaves the column of the gas chromatograph, it enters the mass spectrometer, where it is bombarded with high-energy elec- trons. This bombardment causes the sample to break up into fragments, pro- ducing a fragmentation pattern, or mass spectrum, for each sample. For most compounds, the mass spectrum represents a unique pattern that can be used for identifi cation.

There is tremendous interest in drug-testing programs for use not only in criminal matters but in industry and government as well. Submitting job ap- plicants and employees in the workplace to urine testing for drugs is becom- ing common practice. Likewise, the US military has an extensive urine-testing program for its members. Many urine-testing programs rely on private labo- ratories to perform the required analyses. In any case, when the drug-test results may form the basis for taking action against an individual, both a screening and confi rmation test must be incorporated into the testing proto- col to ensure the integrity of the laboratory’s conclusions.

DETECTING DRUGS IN HAIR When a forensic toxicological examination on a living person is required, the interests of speed and practicality limit the specimens taken to blood and urine. Most drugs remain in the bloodstream for about 24 hours; in urine, they normally are present for up to 72 hours. However, it may be necessary to go farther back in time to ascertain whether a subject has been abusing a drug. If so, the only viable alternative to blood and urine specimens is head hair.

Hair is nourished by blood fl owing through capillaries located close to the hair root. Drugs present in blood diffuse through the capillary walls into the base of the hair and become permanently entrapped in the hair’s hardening protein structure. As the hair continues to grow, the drug’s location on the hair shaft becomes a historical marker for delineating the onset of drug intake. Given that the average human head hair grows at the rate of 1 centimeter per month, analyzing segments of hair for drug content may defi ne the timeline of drug use, tracing it back over a period of weeks, months, or possibly years, depending on the hair’s length.

However, caution is required in interpreting the timeline. The chronology of drug intake may be distorted by drugs that have penetrated the hair’s sur- face as a result of environmental exposure or by drugs that have entered the hair’s surface through sweat. Nevertheless, drug hair analysis is the only vi- able approach for measuring long-term abuse of a drug.

DETECTING NONDRUG POISONS Although forensic toxicologists devote most of their efforts to detecting drugs, they also test for a wide variety of other toxic substances. Some of these are rare elements, not widely or commercially available. Others are so common that virtually everyone is exposed to non- toxic amounts of them every day.

Heavy Metals. One group of poisons once commonly encountered in criminal cases of murder are known as heavy metals . They include arsenic, bismuth, anti- mony, mercury, and thallium. These days, however, the forensic toxicologist only occasionally encounters heavy metals because severe environmental protection regulations restrict their availability to the general public. Nevertheless, as the fol- lowing Case File makes clear, their use is by no means only a historical curiosity.

To screen for many of these metals, the investigator may dissolve the sus- pect body fl uid or tissue in a hydrochloric acid solution and insert a copper strip into the solution. This process is known as the Reinsch test. The appear- ance of a silvery or dark coating on the copper indicates the presence of a heavy metal. Such a fi nding must be confi rmed by analytical techniques suitable for inorganic analysis—namely, emission spectroscopy, or X-ray diffraction.

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Carbon Monoxide. Unlike heavy metals, carbon monoxide is still one of the most common poisons encountered in a forensic laboratory. Inhaling the carbon monoxide from automobile exhaust fumes is a relatively common way to commit suicide (see Figure 12 ). The victim typically uses a garden or vac- uum cleaner hose to connect the tailpipe with the vehicle’s interior or allows the engine to run in a closed garage: A level of carbon monoxide suffi cient to cause death accumulates in fi ve to ten minutes in a closed single-car garage.

When carbon monoxide enters the human body, it is primarily absorbed by the red blood cells, where it combines with hemoglobin to form carboxyhe- moglobin. An average red blood cell contains about 280 million molecules of hemoglobin. Oxygen normally combines with hemoglobin, which transports the oxygen throughout the body. However, if a high percentage of the hemo- globin combines with carbon monoxide, not enough is left to carry suffi cient oxygen to the tissues, and death by asphyxiation quickly follows.

There are two basic methods for measuring the concentration of carbon monoxide in the blood: Spectrophotometric methods examine the visible spectrum of blood to determine the amount of carboxyhemoglobin relative to oxyhemoglobin or total hemoglobin. Alternatively, a volume of blood can be treated with a reagent to liberate the carbon monoxide, which is then mea- sured by gas chromatography.

The amount of carbon monoxide in blood is generally expressed as percent saturation . This represents the extent to which the available hemoglobin has been converted to carboxyhemoglobin. The transition from normal or occupa- tional levels of carbon monoxide to toxic levels is not sharply defi ned. It varies with, among other things, the age, health, and general fi tness of each individual. In a healthy middle-age individual, a carbon monoxide blood saturation greater

CASEFILES JOANN CURLEY: CAUGHT BY A HAIR

A vibrant young woman named Joann Curley rushed to the Wilkes- Barre (Pennsylvania) General Hospital—her husband, Bobby, required immediate medical attention. Bobby was experiencing a burning sen- sation in his feet, numbness in his hands, a fl ushed face, and intense sweating. After being discharged, Bobby experienced another bout of debilitating pain and numbness. He was admitted to another hospi- tal. There doctors observed extreme alopecia, or hair loss.

Test results of Bobby’s urine showed high levels of the heavy metal thallium in his body. Thallium, a rare and highly toxic metal that was used decades ago in substances such as rat poison and to treat ringworm and gout, was found in suffi cient quantities to cause Bobby’s sickness. The use of thallium had been banned in the United States in 1984. Now, at least, Bobby could be treated. However, be- fore Bobby’s doctors could begin treating him for thallium poisoning, he experienced cardiac arrest and slipped into a coma. Joann Curley made the diffi cult decision to remove her husband of thirteen months from life-supporting equipment. He died shortly thereafter.

Investigators learned that Bobby had changed his life insurance to list his wife, Joann, as the benefi ciary of his $300,000 policy. Based on this information, police consulted a forensic toxicologist in an effort to glean as much from the physical evidence in Bobby Curley’s

body as possible. The toxicologist conducted segmental analysis of Bobby’s hair, an analytical method based on the predictable rate of hair growth on the human scalp: an average of 1 centimeter per month. Bobby’s hair was approximately 5 inches (12.5 centimeters) long, which represents almost twelve months of hair growth. Each section tested represented a specifi c period of time in the fi nal year of Bobby’s life.

The hair analysis confi rmed that Bobby Curley had been poi- soned with thallium. The fi rst few doses were small, which prob- ably barely made him feel sick at the time. Gradually, over a year or more, Bobby was receiving more doses of thallium until he fi nally succumbed to a massive dose three or four days before his death. After careful scrutiny of the timeline, investigators concluded that only Joann Curley had access to Bobby during each of these intervals. She also had motive, in the amount of $300,000.

Presented with the timeline and the solid toxicological evidence against her, Joann Curley pleaded guilty to murder. As part of her plea agreement, she provided a forty-page written confession of how she haphazardly dosed Bobby with rat poison she had found in her base- ment. She admitted that she murdered him for the money she would receive from Bobby’s life insurance policy.

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FIGURE 12 Intentionally inhaling carbon monoxide fumes from an automobile is a common way to com- mit suicide. © Dorling Kindersley

than 50 to 60 percent is considered fatal. However, in combination with alcohol or other depressants, fatal levels may be signifi cantly lower. For instance, a car- bon monoxide saturation of 35 to 40 percent may prove fatal in the presence of a blood-alcohol concentration of 0.20 percent w/v. Interestingly, chain smokers may have a constant carbon monoxide level of 8 to 10 percent in normal circum- stances because of the carbon monoxide present in cigarette smoke.

The level of carbon monoxide in the blood of a victim found dead at the scene of a fi re can help ascertain whether foul play has occurred. High levels of carbon monoxide in the blood prove that the victim breathed the combus- tion products of the fi re and was therefore alive when the fi re began. By con- trast, low levels of carbon monoxide indicate that the victim was probably dead before the fi re started, and may have been deliberately placed at the scene in order to destroy the body. Many attempts at covering up a murder by setting fi re to a victim’s house or car have been uncovered in this manner.

SIGNIFICANCE OF TOXICOLOGICAL FINDINGS

Once a drug is found and identifi ed, the toxicologist assesses its infl uence on the behavior of the individual. Interpreting the results of a toxicology fi nding is one of the toxicologist’s most diffi cult chores. Recall that many countries have

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designated a specifi c blood-alcohol level at which an individual is deemed to be under the infl uence of alcohol. These levels were established as a result of numerous studies conducted over several years to measure the effects of alcohol levels on driving performance. However, no such legal guidelines are available to the toxicologist who must judge how a drug other than alcohol affects an individual’s performance or physical state.

For many drugs, blood concentration levels are readily determined and can be used to estimate the pharmacological effects of the drug on the individ- ual. Often, when dealing with a living person, the toxicologist has the added benefi t of knowing what a police offi cer may have observed about an individ- ual’s behavior and motor skills. For a deceased person, drug levels in various body organs and tissues provide additional information about the individual’s state at the time of death. However, before drawing conclusions about drug- induced behavior, the analyst must consider other factors, including the age, physical condition, and tolerance of the drug user.

With prolonged use of a drug, an individual may become less responsive to a drug’s effects and tolerate blood concentrations of the drug that would kill a casual drug user. Therefore, knowledge of an individual’s history of drug use is important in evaluating drug concentrations. Another consideration is the additive or synergistic effects of the interaction of two or more drugs, which may produce a highly intoxicated or comatose state even though none of the drugs alone is present in high or toxic levels. The combination of alcohol with barbiturates or narcotics is a common example of a potentially lethal drug combination.

The amount of a drug in urine is a poor indicator of how extensively an in- dividual’s behavior or state is infl uenced by the drug. Urine is formed outside the body’s circulatory system, and consequently drug levels can build up in it over a relatively long period of time. Some drugs are found in the urine one to three days after they have been taken and long after their effects on the user have disappeared. Nevertheless, the value of this information should not be discounted. Urine drug levels, like blood levels, are best used by law enforce- ment authorities and the courts to corroborate other investigative and medical fi ndings regarding an individual’s condition. Hence, for an individual arrested under suspicion of being under the infl uence of a drug, a toxicologist’s deter- minations supplement the observations of the arresting offi cer, including the results of fi eld sobriety tests and a drug infl uence evaluation (discussed in the following section).

For a deceased person, the medical examiner or coroner must establish a cause of death. However, before a conclusive determination is made, the examining physician depends on the forensic toxicologist to demonstrate the presence or absence of a drug or poison in the tissues or body fl uids of the de- ceased. Only through the combined efforts of the toxicologist and the medical examiner or coroner can society be assured that death investigations achieve high professional and legal standards.

Drug Recognition Experts Although recognizing alcohol-impaired performance is an expertise generally accorded to police offi cers by the courts, recognizing drug-induced intoxica- tion is much more diffi cult and generally not part of police training. During the 1970s, the Los Angeles Police Department developed and tested a series of clinical and psychophysical examinations that a trained police offi cer can use to identify and differentiate among types of drug impairment. This pro- gram has evolved into a national program to train police as drug recognition

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CASEFILES DEATH BY RADIATION POISONING

In November 2006, Alexander V. Litvinenko lay at death’s doorstep in a London hospital. He was in excruciating pain and had symp- toms that included hair loss, an inability to make blood cells, and gastrointestinal distress. His organs slowly failed as he lingered for three weeks before dying. British investigators soon confi rmed that Litvinenko died from the intake of polonium 210, a radioactive ele- ment, in what appeared to be its fi rst use as a murder weapon.

Litvinenko’s death almost immediately set off an international uproar. Litvinenko, a former KBG operative, had became a vocal critic of the Russian spy agency FSB, the domestic successor to the KGB. In 2000, he fl ed to London, where he was granted asylum. Litvinenko had continued to voice his criticisms of the Russian president, Vladi- mir Putin. Just before his death, Litvinenko was believed to have com- piled, on behalf of a British company looking to invest millions in a project in Russia, an incriminating report regarding the activities of senior Kremlin offi cials.

Suspicions immediately fell on Andrei Lugovoi and Dmitri Kov- tun, business associates of Mr. Litvinenko. Lugovoi was himself a for- mer KGB offi cer. On the day he fell ill, Litvinenko had met Lugovoi and Kovtun at the Pine Bar of the Millennium Hotel in London. At the meeting, Mr. Litvinenko drank tea out of a teapot later found to be highly radioactive. British offi cials have accused Lugovoi of poison- ing Litvinenko. Although the precise nature of the evidence against

him still has not been made clear, investigators have linked him and Mr.  Kovtun to a trail of polonium 210 radioactivity in hotel rooms, restaurants, bars, and offi ces stretching from London to Hamburg, Germany, as well as in British Airways planes that had fl own to Moscow. Each man has denied killing Mr. Litvinenko.

Polonium 210 is highly radioactive and very toxic. By weight, it is about 250 million times as toxic as cyanide, so a particle the size of a few grains of sand could be fatal. It emits a radioactive ray known as an alpha particle. Because this form of radiation cannot penetrate the skin, polonium 210 can only be effective as a poison if it is swallowed, breathed in, or injected. The particles disperse through the body and fi rst destroy fast-growing cells such as those in bone marrow, blood, hair, and the digestive tract. This is consistent with Mr.  Litvinenko’s symptoms. There is no antidote for polonium poisoning.

Polonium does have industrial uses and is produced by commer- cial or institutional nuclear reactors. Polonium 210 has been found to be ideal for making antistatic devices that remove dust from fi lm and lenses, as well as from the atmosphere of paper and textile plants. Its non-body-penetrating rays produce an electric charge on nearby air. Bits of dust with static attract the charged air, which neutralizes them. Once free of static, the dust is easy to blow or brush away. Manufacturers of such antistatic devices take great pains to make the polonium hard to remove from their products.

Alexander Litvinenko, former KGB agent, before and after he became sick. (left) Alistair Fuller\AP Wide World Photos; (right) Natasja Weitsz\Getty Images, Inc.–Getty News

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FORENSIC TOXICOLOGY

experts. Normally, a three- to fi ve-month training program is required to cer- tify an offi cer as a drug recognition expert (DRE).

The DRE program incorporates standardized methods for examining sus- pects to determine whether they have taken one or more drugs. The process is systematic and standard: To ensure that each subject has been tested in a rou- tine fashion, each DRE must complete a standard Drug Infl uence Evaluation form (see Figure 13 ). The entire drug evaluation takes approximately thirty to forty minutes. The components of the twelve-step process are summarized in Table 1 .

FIGURE 13 Drug Infl uence Evaluation form. US National Highway Traffi c Safety Administration, Aug., 1999

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FORENSIC TOXICOLOGY

TABLE 1 Components of the Drug Recognition Process

1. Breath-Alcohol Test. By obtaining an accurate and immediate measurement of the suspect’s blood-alcohol concentration, the drug recognition expert (DRE) can determine whether alcohol may be contributing to the suspect’s observable impairment and whether the concentration of alcohol is suffi cient to be the sole cause of that impairment.

2. Interview with the Arresting Offi cer. Spending a few minutes with the arresting offi cer often enables the DRE to determine the most promising areas of investigation.

3. Preliminary Examination. This structured series of questions, specifi c observations, and simple tests provides the fi rst opportunity to examine the suspect closely. It is designed to determine whether the suspect is suffering from an injury or from another condition unrelated to drug consumption. It also affords an opportunity to begin assessing the suspect’s appearance and behavior for signs of possible drug infl uence.

4. Eye Examination. Certain categories of drugs induce nystagmus, an involuntary, spasmodic motion of the eyeball. Nystagmus is an indicator of drug-induced impairment. The inability of the eyes to converge toward the bridge of the nose also indicates the possible presence of certain types of drugs.

5. Divided-Attention Psychophysical Tests. These tests check balance and physical orientation and include the walk and turn, the one- leg stand, the Romberg balance, and the fi nger-to-nose.

6. Vital Signs Examinations. Precise measurements of blood pressure, pulse rate, and body temperature are taken. Certain drugs elevate these signs; others depress them.

7. Dark Room Examinations. The size of the suspect’s pupils in room light, near-total darkness, indirect light, and direct light is checked. Some drugs cause the pupils to either dilate or constrict.

8. Examination for Muscle Rigidity. Certain categories of drugs cause the muscles to become hypertense and quite rigid. Others may cause the muscles to relax and become fl accid.

9. Examination for Injection Sites. Users of certain categories of drugs routinely or occasionally inject their drugs. Evidence of needle use may be found on veins along the neck, arms, and hands.

10. Suspect’s Statements and Other Observations. The next step is to attempt to interview the suspect concerning the drug or drugs he or she has ingested. Of course, the interview must be conducted in full compliance of the suspect’s constitutional rights.

11. Opinions of the Evaluator. Using the information obtained in the previous ten steps, the DRE is able to make an informed decision about whether the suspect is impaired by drugs and, if so, what category or combination of categories is the probable cause of the impairment.

12. Toxicological Examination. The DRE should obtain a blood or urine sample from the suspect for laboratory analysis in order to secure scientifi c, admissible evidence to substantiate his or her conclusions.

The DRE evaluation process can suggest the presence of the following seven broad categories of drugs:

1. Central nervous system depressants 2. Central nervous system stimulants 3. Hallucinogens 4. Dissociative anesthetics (includes phencyclidine and its analogs) 5. Inhalants 6. Narcotic analgesics 7. Cannabis

The DRE program is not designed to be a substitute for toxicological test- ing. The toxicologist can often determine that a suspect has a particular drug in his or her body, but the toxicologist often cannot infer with reasonable cer- tainty that the suspect was impaired at a specifi c time. On the other hand, the DRE can supply credible evidence that the suspect was impaired at a specifi c time and that the nature of the impairment was consistent with a particular family of drugs. However, the DRE program usually cannot determine which specifi c drug was ingested. Proving drug intoxication requires a coordinated effort and the production of competent data from both the DRE and the foren- sic toxicologist.

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FORENSIC TOXICOLOGY

Quick Review • The forensic toxicologist must devise an analytical scheme to detect, iso-

late, and identify toxic drug substances extracted from biological fl uids, tissues, and organs.

• A screening test gives quick insight into the likelihood that a specimen contains a drug substance. Positive results arising from a screening test are tentative at best and must be verifi ed with a confi rmation test.

• The most widely used screening tests are thin-layer chromatography, gas chromatography, and immunoassay. Gas chromatography/mass spec- trometry is generally accepted as the confi rmation test of choice.

• Once a drug is extracted and identifi ed, a toxicologist may be required to judge the drug’s effect on an individual’s natural performance or physical state.

• A three- to fi ve-month training program is required to certify an offi cer as a drug recognition expert (DRE). This training incorporates standardized methods for examining suspects to determine whether they have taken one or more drugs.

VIRTUAL LAB Blood Alcohol Analysis To perform a virtual blood alcohol analysis, go to www .pearsoncustom.com/us/vlm/

CHAPTER REVIEW

• Forensic toxicologists detect and identify drugs and poisons in body fl uids, tissues, and organs in situations that involve violations of criminal laws.

• Ethyl alcohol is the most heavily abused drug in Western countries.

• Alcohol appears in the blood within minutes after it has been taken by mouth. It slowly increases in concentration while it is being absorbed from the stomach and the small intestine into the bloodstream.

• When all the alcohol has been absorbed, a maximum alcohol level is reached in the blood, and the postabsorption period begins. During postabsorption, the alcohol concentration slowly decreases until a zero level is reached.

• Elimination of alcohol throughout the body is accomplished through oxidation and excretion. Oxidation takes place al- most entirely in the liver, whereas alcohol is excreted un- changed in the breath, urine, and perspiration.

• Breath-testing devices operate on the principle that the ratio between the concentration of alcohol in alveolar breath and its concentration in blood is fi xed.

• Modern breath testers are free of chemicals. They include in- frared light absorption devices and fuel cell detectors.

• The key to the accuracy of a breath-testing device is to en- sure that the unit captures the alcohol in the alveolar (deep- lung) breath of the subject.

• Many breath testers collect a set volume of breath and expose it to infrared light. The instrument measures the concentration of alcohol in the collected breath sample by measuring the degree of interaction between the light and the alcohol present.

• Law enforcement offi cers use fi eld sobriety tests to estimate a motorist’s degree of physical impairment from alcohol and to determine whether an evidential test for alcohol is justifi ed.

• The horizontal-gaze nystagmus test, the walk and turn, and the one-leg stand are all considered reliable and effective psychophysical tests for alcohol impairment.

• Gas chromatography is the most widely used approach for determining blood-alcohol levels in forensic laboratories.

• An anticoagulant should be added to a blood sample to pre- vent clotting; a preservative should be added to inhibit the growth of microorganisms capable of destroying alcohol.

• The current legal measure of drunk driving in the United States is a blood-alcohol concentration of 0.08 percent, or 0.08 grams of alcohol per 100 milliliters of blood.

• The implied-consent law states that the operator of a motor vehicle on a public highway must either consent to a test for alcohol intoxication, if requested, or lose his or her license for some designated period—usually six months to one year.

• The forensic toxicologist must devise an analytical scheme to detect, isolate, and identify toxic drug substances extracted from biological fl uids, tissues, and organs.

• A screening test gives quick insight into the likelihood that a specimen contains a drug substance. Positive results arising from a screening test are tentative at best and must be veri- fi ed with a confi rmation test.

• The most widely used screening tests are thin-layer chroma- tography, gas chromatography, and immunoassay. Gas chro- matography/mass spectrometry is generally accepted as the confi rmation test of choice.

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REVIEW QUESTIONS

• Once a drug is extracted and identifi ed, a toxicologist may be required to judge the drug’s effect on an individual’s natural performance or physical state.

• A three- to fi ve-month training program is required to certify an offi cer as a drug recognition expert (DRE). This training incorporates standardized methods for examining suspects to determine whether they have taken one or more drugs.

1. The ______________ studies body fl uids, tissues, and or- gans to detect and identify drugs and poisons.

2. True or False: Toxicologists are employed only by crime labo- ratories. ______________

3. The most heavily abused drug in the Western world is ______________ .

4. The transformation of chemicals introduced into the body into substances that are easier to eliminate is called ______________ .

5. Alcohol consumed on an empty stomach is absorbed (faster, slower) than an equivalent amount of alcohol taken when there is food in the stomach.

6. Alcohol is eliminated from the body by ______________ and ______________ .

7. Approximately 98 percent of the ethyl alcohol consumed is ox- idized to carbon dioxide and water in the ______________ .

8. The amount of alcohol exhaled in the ______________ is directly proportional to the concentration of alcohol in the blood.

9. Alcohol is eliminated from the blood at an average rate of ______________ percent w/v.

10. True or False: The amount of alcohol in the blood is not di- rectly proportional to the concentration of alcohol in the brain. ______________

11. True or False: Blood-alcohol levels have become the accepted standard for relating alcohol intake to its effect on the body. ______________

12. Under normal drinking conditions, alcohol concentration in the blood peaks in ______________ to ______________ minutes.

13. A(n) ______________ carries blood away from the heart; a(n) ______________ carries blood back to the heart.

14. The ______________ artery carries deoxygenated blood from the heart to the lungs.

15. Alcohol passes from the blood capillaries into the ______________ sacs in the lungs.

16. One milliliter of blood contains the same amount of alcohol as approximately ______________ milliliters of alveolar breath.

17. True or False: When alcohol is being absorbed into the blood, the alcohol concentration in venous blood is higher than that in arterial blood. ______________

18. True or False: Portable, handheld, roadside breath testers for alcohol provide evidential test results. ______________

19. Most modern breath testers use ______________ radiation to detect and measure alcohol in the breath.

20. In an alcohol ______________ , two platinum electrodes are separated by an acid- or base-containing porous mem- brane, and one of the electrodes is positioned to come into contact with a subject’s breath sample.

21. To avoid the possibility of testing “mouth alcohol,” the op- erator of a breath tester must not allow the subject to take any foreign materials into the mouth for ______________ to ______________ minutes prior to the test.

22. True or False: A series of reliable and effective psychophysical tests are the horizontal-gaze nystagmus, the walk and turn, and the one-leg stand. ______________

23. Alcohol can be separated from other volatiles in blood and measured by the technique of ______________ .

24. When drawing blood for alcohol testing, the breath- test operator must fi rst wipe the suspect’s skin with a(n) ______________ disinfectant.

25. True or False: Failure to add a preservative, such as sodium fl uoride, to blood removed from a living person may lead to a decline in alcohol concentration. ______________

26. Most states have established ______________ percent w/v as the impairment limit for blood-alcohol concentration in noncommercial drivers.

KEY TERMS

absorption

acid

alveoli

anticoagulant

artery

base

capillary

excretion

fuel cell detector

metabolism

oxidation

pH

preservative

toxicologist

vein

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FORENSIC TOXICOLOGY

APPLICATION AND CRITICAL THINKING

27. Studies show that an individual is about ______________ times as likely to become involved in an automobile accident at the legal limit for blood alcohol as a sober individual.

28. In the case of ______________ , the Supreme Court ruled that taking nontestimonial evidence, such as a blood sample, did not violate a suspect’s Fifth Amendment rights.

29. After entering the body, heroin is changed into ______________ .

30. The body fl uids ______________ and ______________ are both desirable for the toxicological examination of a liv- ing person suspected of being under the infl uence of a drug.

31. A large number of drugs can be classifi ed chemically as ______________ or ______________ .

32. True or False: Water with a pH value of less than 7 is basic. ______________

33. Drugs are extracted from body fl uids and tissues by carefully controlling the ______________ of the medium in which the sample has been dissolved.

34. Both ______________ and ______________ tests must be incorporated into the drug-testing protocol of a toxicol- ogy laboratory to ensure the correctness of the laboratory’s conclusions.

35. The most widely used screening tests used by toxi- cologists are ______________ , ______________ , and ______________ .

36. The preferred method for confi rmation testing is a combi- nation of ______________ and ______________ , which creates a unique pattern that can be used for identifi cation.

37. A toxicologist may be able to detect and identify a long- abused drug or poison because drugs present in blood diffuse through capillary walls into the base of a(n) ______________ and become permanently entrapped in its hardening protein structure.

38. The gas ______________ combines with hemoglobin in the blood to form carboxyhemoglobin, thus interfering with the transportation of oxygen in the blood.

39. True or False: Blood levels of drugs can be used alone to draw defi nitive conclusions about the effects of a drug on an indi- vidual. ______________

40. True or False: The level of a drug present in the urine is by itself a poor indicator of how extensively an individual is af- fected by a drug. ______________

41. Urine and blood drug levels are best used by law enforce- ment authorities and the courts to ______________ other investigative and medical fi ndings pertaining to an individu- al’s condition.

42. A program to train police as ______________ incorporates systematic and standardized methods for examining sus- pects to determine whether they have taken one or more drugs.

1. Answer the following questions about driving risk associated with drinking and blood-alcohol concentrations:

a) Randy is just barely legally intoxicated. How much more likely is he to have an accident than someone who is sober?

b) Marissa, who has been drinking, is fi fteen times as likely to have an accident as her sober friend, Christine. What is Marissa’s approximate blood-alcohol concentration?

c) After several drinks, Charles is ten times as likely to have an accident as a sober person. Is he more or less intoxi- cated than James, whose blood alcohol level is 0.10?

d) Under the original blood-alcohol standards recom- mended by the National Highway Traffi c Safety Ad- ministration, a person considered just barely legally intoxicated was how much more likely to have an ac- cident than a sober individual?

2. Following are descriptions of four individuals who have been drinking. Rank them by blood-alcohol concentration, from highest to lowest:

a) John, who weighs 200 pounds and has consumed eight 8-ounce drinks on a full stomach

b) Frank, who weighs 170 pounds and has consumed four 8-ounce drinks on an empty stomach

c) Gary, who weighs 240 pounds and has consumed six 8-ounce drinks on an empty stomach

d) Stephen, who weighs 180 pounds and has consumed six 8-ounce drinks on a full stomach

3. Following are descriptions of four individuals who have been drinking. In which (if any) of the following countries would each be considered legally drunk: the United States, Austra- lia, and/or Sweden?

a) Bill, who weighs 150 pounds and has consumed three 8-ounce drinks on an empty stomach

b) Sally, who weighs 110 pounds and has consumed three 8-ounce drinks on a full stomach

c) Rich, who weighs 200 pounds and has consumed six 8-ounce drinks on an empty stomach

d) Carrie, who weighs 140 pounds and has consumed four 8-ounce drinks on a full stomach

4. You are a forensic scientist who has been asked to test two blood samples. You know that one sample is suspected of containing barbiturates and the other contains no drugs; however, you cannot tell the two samples apart. Describe how you would use the concept of pH to determine which sample contains barbiturates. Explain your reasoning.

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ENDNOTES

1. In the United States, laws that defi ne blood-alcohol levels almost exclusively use the unit percent weight per volume —% w/v. Hence, 0.015 percent w/v is equivalent to 0.015 gram of alcohol per 100 milliliters of blood, or 15 milligrams of alcohol per 100 milliliters.

2. R. B. Forney et al., “Alcohol Distribution in the Vascular System: Concentrations of Orally Administered Alcohol in Blood from Various Points in the Vascular System and in Rebreathed Air During Absorption,” Quarterly Journal of Studies on Alcohol 25 (1964): 205.

3. G. A. Brown et al., “The Stability of Ethanol in Stored Blood,” Analytica Chemica Acta 66 (1973): 271.

4. 0.15 percent w/v is equivalent to 0.15 grams of alcohol per 100 milliliters of blood, or 150 milligrams per 100 milliliters.

5. 384 U.S. 757 (1966).

5. You are investigating an arson scene and you fi nd a corpse in the rubble, but you suspect that the victim did not die as a result of the fi re. Instead, you suspect that the victim was

murdered earlier and that the blaze was intentionally started to cover up the murder. How would you go about determin- ing whether the victim died before the fi re?

360

JEFFREY MACDONALD: FATAL VISION The grisly murder scene that confronted police on February 17, 1970, is one that would not be wiped from memory. Summoned to the Fort Bragg residence of Captain Jeffrey MacDonald, a physician, police found the bludgeoned body of MacDonald’s wife. She had been repeatedly

knifed, and her face was smashed to a pulp. MacDonald’s two children, ages 2 and 5, had been brutally and repeatedly knifed and battered to death.

Suspicion quickly fell on MacDon- ald. To the eyes of investigators, the murder scene had a staged appearance. MacDonald described a frantic effort to subdue four intruders who had slashed at him with an ice pick. However, the confrontation left MacDonald with minor wounds and no apparent defen- sive wounds on his arms. MacDonald then described how he had covered his slashed wife with his blue pajama top. Interestingly, when the body was removed, blue threads were observed under the body. In fact, blue threads matching the pajama top turned up throughout the house—nineteen in one

child’s bedroom, including one beneath her fi ngernail, and two in the other child’s bedroom. Eighty-one blue fi bers were recovered from the master bedroom, and two were located on a bloodstained piece of wood outside the house.

Forensic examination showed that the forty-eight ice pick holes in the pajama top were smooth and cy- lindrical, a sign that the top was stationary when it was slashed. Also, folding the pajama top demonstrated that the forty-eight holes actually could have been made by twenty-one thrusts of an ice pick. This coincided with the number of wounds that MacDonald’s wife sustained. As described in the book Fatal Vision , which chronicles the murder investigation, when MacDonald was confronted with adulterous conduct, he replied, “You guys are more thorough than I thought.” MacDonald is currently serv- ing three consecutive life sentences.

LEARNING OBJECTIVES After studying this chapter, you should be able to: • Recognize and understand the cuticle, cortex, and medulla

areas of hair. • List the three phases of hair growth. • Appreciate the distinction between animal and human hairs. • List hair features that are useful for microscopic comparisons

of human hairs. • Explain the proper collection of forensic hair evidence. • Describe and understand the role of DNA typing in hair

comparisons. • Understand the differences between natural and

manufactured fi bers. • List the properties of fi bers that are most useful for forensic

comparisons. • Describe the proper collection of fi ber evidence.

Trace

Evidence I Hairs and Fibers

© Bettmann/CORBIS All Rights Reserved

From Chapter 13 of Forensic Science: From the Crime Scene to the Crime Lab. Second Edition. Richard Saferstein. Copyright © 2013 by Pearson Education, Inc. All rights reserved.

TRACE EVIDENCE I

T he trace evidence transferred between individuals and objects during the commission of a crime, if recovered, often corroborates other evidence developed during the course of an investigation. Although in most cases

physical evidence cannot by itself positively identify a suspect, laboratory ex- amination may narrow the origin of such evidence to a group that includes the suspect. Using many of the instruments and techniques we have already ex- amined, the crime laboratory has developed a variety of procedures for com- paring and tracing the origins of physical evidence. This chapter will focus on the value of hairs and fi bers as physical evidence.

Forensic Examination of Hair Hair is encountered as physical evidence in a wide variety of crimes. However, any review of the forensic aspects of hair examination must start with the ob- servation that it is not yet possible to individualize a human hair to any single head or body through its morphology, or structural characteristics. Over the years, criminalists have tried to isolate the physical and chemical properties of hair that could serve as individual characteristics of identity. Partial success has fi nally been achieved by isolating and characterizing the DNA present in hair.

The importance of hair as physical evidence cannot be overemphasized. Its removal from the body often denotes physical contact between a victim and perpetrator and hence a crime of a serious or violent nature. When hair is properly collected at the crime scene and submitted to the laboratory along with enough standard/reference samples, it can provide strong corroborative evidence for placing an individual at a crime site. The fi rst step in the forensic examination of hair logically starts with its color and structure (i.e., morphol- ogy) and, if warranted, progresses to the more detailed DNA extraction, isola- tion, and characterization.

MORPHOLOGY OF HAIR

Hair is an appendage of the skin that grows out of an organ known as the hair follicle . The length of a hair extends from its root, or bulb, which is embedded in the follicle, continues into the shaft, and terminates at the tip. The shaft, which is composed of three layers—the cuticle , cortex , and medulla —is most intensely examined by the forensic scientist (see Figure 1 ). CUTICLE Two features that make hair a good subject for establishing indi- vidual identity are its resistance to chemical decomposition and its ability to retain structural features over a long period of time. Much of this resistance and stability is attributed to the cuticle, a scale structure covering the exterior of the hair. The cuticle is formed by overlapping scales that always point to- ward the tip end of each hair. The scales form from specialized cells that have hardened ( i.e., keratinized) and fl attened in progressing from the follicle. There are three basic patterns that describe the appearance of the cuticle: cornal, spinous, and imbricate (see Figure 2 ).

Although the scale pattern is not a useful characteristic for individualizing human hair, the variety of patterns formed by animal hair makes it an impor- tant feature for species identifi cation. Figure 3 shows the scale patterns of some animal hairs and of a human hair as viewed with a scanning electron microscope. Another method of studying the scale pattern of hair is to make a cast of its surface. This is done by embedding the hair in a soft medium, such as clear nail polish or softened vinyl. When the medium has hardened, the hair is removed, leaving a clear, distinct impression of the hair’s cuticle, ideal for examination with a compound microscope.

cuticle The scale structure covering the exterior of the hair.

cortex The main body of the hair shaft.

medulla A cellular column running through the center of the hair.

362

TRACE EVIDENCE I

Cortex Cuticle

Follicle Root

FIGURE 1 A cross-section of skin showing hair growing out of a tubelike structure called the follicle.

CORTEX Contained within the protective layer of the cuticle is the cortex, the main body of the hair shaft. The cortex is made up of spindle-shaped cortical cells aligned in a regular array, parallel to the length of the hair. The cortex derives its major forensic importance from the fact that it is embedded with the pigment granules that give hair its color. The color, shape, and distribution of these granules provide important points of comparison among the hairs of different individuals.

FIGURE 2 (a) The coronal, or crownlike, scale pattern resembles a stack of paper cups. (b) Spinous or petal-like scales are triangular in shape and protrude from the hair shaft. (c) The imbricate, or fl attened- scale, type consists of overlapping scales with narrow margins. Richard Saferstein, Ph.D.

(a)

(c)

(b)

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TRACE EVIDENCE I

The structural features of the cortex are examined microscopically after the hair has been mounted in a liquid medium with a refractive index close to that of the hair. Under these conditions, the amount of light refl ected off the hair’s surface is minimized, and the amount of light penetrating the hair is optimized.

MEDULLA The medulla is a collection of cells that looks like a central canal running through a hair. In many animals, this canal is a predominant feature, occupying more than half of the hair’s diameter. The medullary index mea- sures the diameter of the medulla relative to the diameter of the hair shaft and is normally expressed as a fraction. For humans, the index is generally less than one-third; for most other animals, the index is one-half or greater.

The presence and appearance of the medulla vary from individual to in- dividual and even among the hairs of a given individual. Not all hairs have medullae, and when they do exist, the degree of medullation can vary. In this respect, medullae may be classifi ed as being either continuous, interrupted, fragmented, or absent (see Figure 4 ). Human head hairs generally exhibit no medullae or have fragmented ones; they rarely show continuous medullation. One noted exception is in people of the Mongoloid race, who usually have head hairs with continuous medullae. Also, most animals have medullae that are either continuous or interrupted.

FIGURE 3 Scale patterns of various types of hair: (a) hu- man head hair (600�), (b) dog (1350�), (c) deer (120�), (d) rabbit (300�), (e) cat (2000�), and (f) horse (450�).

Continuous Interrupted Fragmented

FIGURE 4 Medulla patterns.

(a) (c)

(e) (f)

(b)

(d)

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TRACE EVIDENCE I

Another interesting feature of the medulla is its shape. Humans, as well as many animals, have medullae that give a nearly cylindrical appearance. Other animals exhibit medullae that have a patterned shape. For example, the medulla of a cat can best be described as resembling a string of pearls, whereas members of the deer family show a medullary structure consisting of spherical cells occupying the entire hair shaft. Figure 5 illustrates med- ullary sizes and forms for a number of common animal hairs and a human head hair.

A searchable database on CD-ROM of the thirty-fi ve most common ani- mal hairs encountered in forensic casework is commercially available. 1 This database allows an examiner to rapidly search for animal hairs based on scale patterns and/or medulla type using a PC. A typical screen presentation arising from such a data search is shown in Figure 6 .

ROOT The root and other surrounding cells within the hair follicle provide the tools necessary to produce hair and continue its growth. Human head hair grows in three developmental stages, and the shape and size of the hair root is determined by the hair’s current growth phase. The three phases of hair growth are the anagen , catagen , and telogen phases .

anagen phase The initial growth phase during which the hair follicle actively produces hair.

catagen phase A transition stage between the anagen and telogen phases of hair growth.

telogen phase The fi nal growth phase in which hair naturally falls out of the skin.

(e)

FIGURE 5 Medulla patterns for various types of hair: (a) human head hair (400�), (b) dog (400�), (c) deer (500�), (d) rabbit (450�), (e) cat (400�), and (f) mouse (500�).

(a) (c)

(f)

(b) (d)

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TRACE EVIDENCE I

In the anagen phase (the initial growth phase), which may last up to six years, the root is attached to the follicle for continued growth, giving the root bulb a fl ame-shaped appearance ( Figure 7 [a]). When pulled from the root, some hairs in the anagen phase have a follicular tag . With the advent of DNA analysis, this follicular tag is important for individualizing hair.

Hair continues to grow, but at a decreasing rate, during the catagen phase, which can last anywhere from two to three weeks. In the catagen phase, roots typically take on an elongated appearance ( Figure 7 [b]) as the root bulb shrinks and is pushed out of the hair follicle. Once hair growth ends, the telogen phase begins and the root takes on a club-shaped appearance ( Figure  7 [c]). Over two to six months, the hair is pushed out of the follicle, causing the hair to be naturally shed.

FIGURE 6 Information on rabbit hair contained within the Forensic Animal Hair Atlas. Courtesy RJ Lee Group, Inc. Monroeville, PA

(a)

(b)

(c)

FIGURE 7 Hair roots in the (a) anagen phase, (b) catagen phase, and (c) telogen phase (100�). Courtesy Charles A. Linch

follicular tag A translucent piece of tissue surrounding the hair’s shaft near the root that contains the richest source of DNA associated with hair.

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TRACE EVIDENCE I

IDENTIFICATION AND COMPARISON OF HAIR

Most often the prime purpose for examining hair evidence in a crime labora- tory is either to establish whether the hair is human or animal in origin or to determine whether human hair retrieved at a crime scene compares with hair from a particular individual. A careful microscopic examination of hair reveals morphological features that can distinguish human hair from animal hair. The hair of various animals also differs enough in structure that the examiner can often identify the species. Before reaching such a conclusion, however, the ex- aminer must have access to a comprehensive collection of reference standards and the accumulated experience of hundreds of prior hair examinations. Scale structure, medullary index, and medullary shape are particularly important in hair identifi cation.

The most common request when hair is used as forensic evidence is to de- termine whether hair recovered at the crime scene compares to hair removed from a suspect. In most cases, such a comparison relates to hair obtained from the scalp or pubic area. Ultimately, the evidential value of the comparison de- pends on the degree of probability with which the examiner can associate the hair in question with a particular individual.

FACTORS IN COMPARISON OF HAIR Although animal hair normally can be distinguished from human hair with little diffi culty, human hair compari- sons must be undertaken with extreme caution. Hair tends to exhibit variable morphological characteristics, not only from one person to another but also within a single individual. In comparing hair, the criminalist is particularly in- terested in matching color, length, and diameter. Other important features are the presence or absence of a medulla and the distribution, shape, and color in- tensity of the pigment granules in the cortex. A microscopic examination may also distinguish dyed or bleached hair from natural hair. A dyed color is often present in the cuticle as well as throughout the cortex. Bleaching, on the other hand, tends to remove pigment from the hair and gives it a yellowish tint.

If hair has grown since it was last bleached or dyed, the natural-end por- tion will be quite distinct in color. An estimate of the time since dyeing or bleaching can be made because hair grows approximately 1 centimeter per month. Other signifi cant but less frequent features may be observed in hair. For example, morphological abnormalities may be present as a result of cer- tain diseases or nutrient defi ciencies. Also, the presence of fungal and nit in- fections can further link a hair specimen to a particular individual.

MICROSCOPIC EXAMINATION OF HAIR A comparison microscope is an in- valuable tool that allows the examiner to view the questioned and known hair together, side by side. Any variations in the microscopic characteristics will thus be readily observed. Because hair from any part of the body exhibits a range of characteristics, it is necessary to have an adequate number of known hairs that are representative of all its features when making a comparison.

Although the microscopic comparison of hairs has long been accepted as an appropriate approach for including and excluding questioned hairs against standard/reference hairs, many forensic scientists have long recognized that this approach is very subjective and is highly dependent on the skills and in- tegrity of the analyst, as well as the hair morphology being examined. How- ever, until the advent of DNA analysis, the forensic science community had no choice but to rely on the microscope to carry out hair comparisons.

Any lingering doubts about the necessity of augmenting microscopic hair examinations with DNA analysis evaporated with the publication of an FBI study describing signifi cant error rates associated with microscopic compari- son of hairs. 2 Hair evidence submitted to the FBI for DNA analysis between 1996 and 2000 was examined both microscopically and by DNA analysis.

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TRACE EVIDENCE I

Approximately 11 percent of the hairs (nine out of eighty) in which FBI hair examiners found a positive microscopic match between questioned and stan- dard/reference hairs were found to be nonmatches when they were later subjected to DNA analysis. The course of events is clear: Microscopic hair comparisons must be regarded by police and courts as presumptive in nature, and all positive microscopic hair comparisons must be confi rmed by DNA determinations.

QUESTIONS ABOUT HAIR EXAMINATION A number of questions may be asked to further ascertain the present status of forensic hair examinations. The answers to these questions can be of great signifi cance to the investigator working with hair evidence.

Can the Body Area from Which a Hair Originated Be Determined? Nor- mally it is easy to determine the body area from which a hair came. For ex- ample, scalp hairs generally show little diameter variation and have a more uniform distribution of pigment when compared to other body hairs. Pubic hairs are short and curly, with wide variations in shaft diameter, and usually have continuous medullae. Beard hairs are coarse, are normally triangular in cross-section, and have blunt tips acquired from cutting or shaving.

Can the Racial Origin of Hair Be Determined? In many instances, the examiner can distinguish hair originating from members of different races; this is especially true of Caucasian and Negroid head hair. Negroid hairs are normally kinky, containing dense, unevenly distributed pigments. Caucasian hairs are usually straight or wavy, with very fi ne to coarse pigments that are more evenly distributed when compared to Negroid hair. Mongoloid hairs of- ten have a dense pigment distribution, but they normally don’t exhibit the pig- ment clumping seen in Negroid hairs. Mongoloids also tend to have thicker hair shaft diameters when compared to the other two races.

Sometimes a cross-sectional examination of hair may help identify race. Cross-sections of hair from Caucasians are oval to round in shape, Mongoloid generally exhibit a round cross-sectional shape, and cross-sections of Negroid hair are fl at to oval in shape. However, all of these observations are general, with many possible exceptions. The criminalist must approach the determina- tion of race from hair with caution and a good deal of experience.

Can the Age and Sex of an Individual Be Determined from a Hair Sample? The age of an individual cannot be learned from a hair examination with any degree of certainty except in the case of infant hairs, which are fi ne and short and have fi ne pigmentation. Although the presence of dye or bleach on the hair may offer some clue to sex, present hairstyles make these charac- teristics less valuable than they were in the past. The recovery of nuclear DNA either from tissue adhering to a hair or from the root structure of the hair will allow a determination of whether the hair originated from a male or female.

Is It Possible to Determine Whether Hair Was Forcibly Removed from the Body? A microscopic examination of the hair root may establish whether the hair fell out or was pulled out of the skin. A hair root with follicular tissue (root sheath cells) adhering to it, as shown in Figure 8 , indicates a hair that has been pulled out either by a person or by brushing or combing. Hair naturally falling off the body has a bulbous-shaped root free of any adhering tissue.

The absence of sheath cells cannot always be relied on for correctly judg- ing whether hair has been forcibly pulled from the body. In some cases the root of a hair is devoid of any adhering tissue even when it has been pulled from the body. Apparently, an important consideration is how quickly the hair is pulled out of the head. Hairs pulled quickly from the head are much more likely to have sheath cells compared to hairs that have been removed slowly from the scalp. 3

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TRACE EVIDENCE I

CASEFILES CENTRAL PARK JOGGER CASE REVISITED

On April 19, 1989, a young woman left her apartment around nine p.m. to jog in New York’s Central Park. Nearly fi ve hours later, she was found comatose lying in a puddle of mud in the park. She had been raped, her skull was fractured, and she had lost 75 percent of her blood. When the woman recovered, she had no memory of what happened to her. The brutality of the crime sent shock waves through the city and seemed to fuel a national perception that crime was run- ning rampant and unchecked through the streets of New York.

Already in custody at the station house of the Central Park Pre- cinct was a group of 14- and 15-year-old boys who had been rounded up leaving the park earlier in the night by police who suspected that they had been involved in a series of random attacks. Over the next two days, four of the teenagers gave videotaped statements, which they later recanted, admitting to participating in the attack. Ulti- mately, fi ve of the teenagers were charged with the crime.

Interestingly, none of the semen collected from the victim could be linked to any of the defendants. However, according to the testi- mony of a forensic analyst, two head hairs collected from the clothing of one of the defendants microscopically compared to those of the victim, and a third hair collected from the same defendant’s T-shirt microscopically compared to the victim’s pubic hair. Besides these three hairs, a fourth hair was found to be microscopically similar to the victim’s. This hair was recovered from the clothing of Steven Lopez, who was originally charged with rape but not prosecuted for the crime.

Hairs were the only pieces of physical evidence offered by the dis- trict attorney to directly link any of the teenagers to the crime. The hairs were cited by the district attorney as proof for the jury that the video- taped confessions of the teenagers were reliable. The fi ve defendants were convicted and ultimately served from nine to thirteen years.

In August 1989, more than three months after the jogger attack, New York police arrested a man named Matias Reyes, who pleaded guilty to murdering a pregnant woman, raping three other women, and committing a robbery. For these crimes Reyes was sentenced to thirty-three years to life. In January 2002, Reyes also confessed to the Central Park attack. Follow-up tests revealed that Reyes’s DNA compared to semen recovered from the jogger’s body and her sock. Other DNA tests showed that the hairs offered into evidence at the original trial did not come from the victim and so could not be used to link the teenagers to the crime as the district attorney had argued. After an eleven-month reinvestigation of the original charges, a New York State Supreme Court judge dismissed all the convictions against the five teenage suspects in the Central Park jogger case.

Courtesy AP Wide World Photos

FIGURE 8 Forcibly removed head hair with follicular tissue attached.

369

TRACE EVIDENCE I

Are Efforts Being Made to Individualize Human Hair? Forensic scientists routinely isolate and characterize individual variations in DNA. Forensic hair examiners can link human hair to a particular individual by characterizing the nuclear DNA in the hair root or in follicular tissue adhering to the root (see Figure 8 ). Recall that the follicular tag is the richest source of DNA associated with hair. In the absence of follicular tissue, an examiner must extract DNA from the hair root.

The growth phase of hair is a useful predictor of the likelihood of suc- cessfully typing DNA in human hair. 4 Examiners have a higher success rate in extracting DNA from hair roots in the anagen phase or from anagen-phase hairs entering the catagen phase of growth. Telogen-phase hairs have an in- adequate amount of DNA for typing. Because most hairs are naturally shed and are expected to be in the telogen stage, these observations do not por- tend well for hairs collected at crime scenes. However, some crime scenes are populated with forcibly removed hairs that are expected to be rich sources for nuclear DNA.

When a questioned hair does not have adhering tissue or a root struc- ture amenable to isolation of nuclear DNA, there is an alternative source of information: mitochondrial DNA . Unlike the nuclear DNA described earlier, which is located in the nuclei of practically every cell in the body, mitochon- drial DNA is found in cellular material outside the nucleus. Interestingly, un- like nuclear DNA, which is passed down from both parents, mitochondrial DNA is transmitted only from mother to child. Importantly, many more cop- ies of mitochondrial DNA than nuclear DNA are located in the cells. For this reason, the success rate of fi nding and typing mitochondrial DNA is much greater from samples that have limited quantities of nuclear DNA, such as hair. Hairs 1 to 2 centimeters long can be subjected to mitochondrial analysis with extremely high odds of success.

Can DNA Individualize a Human Hair? In some cases, the answer is yes. Nuclear DNA produces frequencies of occurrence as low as one in billions or trillions. On the other hand, mitochondrial DNA cannot individualize human hair. However, its diversity within the human population often permits the exclusion of a signifi cant portion of a population as potential contributors of a hair sample. Ideally, the combination of a positive microscopic comparison and an association through nuclear or mitochondrial DNA analysis strongly links a questioned hair and standard/reference hairs. However, a word of caution: Mitochondrial DNA cannot distinguish microscopically similar hairs from individuals who are maternally related.

COLLECTION AND PRESERVATION

OF HAIR EVIDENCE

When questioned hairs are submitted to a forensic laboratory for examina- tion, they must always be accompanied by an adequate number of standard/ reference samples from the victim of the crime and from individuals suspected of having deposited hair at the crime scene. We have learned that hair from different parts of the body varies signifi cantly in its physical characteristics. Likewise, hair from any one area of the body can also have a wide range of characteristics. For this reason, the questioned and standard/reference hairs must come from the same area of the body; one cannot, for instance, compare head hair to pubic hair. It is also important that the collection of standard/ reference hair be carried out in a way that ensures a representative sampling of hair from any one area of the body.

nuclear DNA DNA that is present in the nucleus of a cell and that is inherited from both parents.

mitochondrial DNA DNA present in small structures (i.e., mitochondria) outside the nucleus of a cell. Mitochondria supply energy to the cell. This form of DNA is inherited maternally (from the mother).

370

TRACE EVIDENCE I

Forensic hair comparisons generally involve either head hair or pubic hair. Collecting fi fty full-length hairs from all areas of the scalp normally en- sures a representative sampling of head hair. Likewise, a minimum collection of twenty-four full-length pubic hairs should cover the range of characteris- tics present in this type of hair. In rape cases, care must fi rst be taken to comb the pubic area with a clean comb to remove all loose foreign hair present be- fore the victim is sampled for standard/reference hair. The comb should then be packaged in a separate envelope.

Because a hair may vary in color and other morphological features over its entire length, the entire hair is collected. This requirement is best accom- plished by either pulling the hair out of the skin or clipping it at the skin line. During an autopsy, hair samples are routinely collected from victims of suspi- cious deaths. Because the autopsy may occur early in an investigation, the need for hair standard/reference samples may not always be apparent. How- ever, one should never rule out the possible involvement of hair evidence in subsequent investigative fi ndings. Failure to make this simple collection may result in complicated legal problems later.

Quick Review • The hair shaft is composed of three layers called the cuticle, cortex, and

medulla and is the part of a hair most intensely examined by the forensic scientist.

• When comparing strands of hair, the criminalist is particularly interested in matching the color, length, and diameter. Other important features for comparing hair are the presence or absence of a medulla and the distribu- tion, shape, and color intensity of pigment granules in the cortex.

• The likelihood of successfully detecting DNA in hair roots is higher in hair being examined in its anagen or early growth phase than in its catagen or telogen phases.

CASEFILES The murder of Ennis Cosby, son of entertainer Bill Cosby, at fi rst ap- peared unsolvable. It was a random act. When his car tire went fl at, En- nis pulled off the road and called a friend on his cellular phone to ask for assistance. Shortly thereafter, an assailant demanded money and, when Cosby didn’t respond quickly enough, shot him once in the tem- ple. Acting on a tip from a friend of the assailant, police investigators later found a .38-caliber revolver wrapped in a blue cap miles from

the crime scene. Mikail Markhasev was arrested and charged with murder.

At the trial, the district attorney introduced fi rearms evidence to show that the recovered gun had fi red the bullet that killed Cosby. A single hair also recovered from the hat dramatically linked Markhasev to the crime: Los Angeles Police Department forensic analyst Harry Klann identifi ed six DNA markers from the follicular tissue adhering to the hair root that matched Markhasev’s DNA. This particular DNA profi le is found in 1 out of 15,500 members of the general popula- tion. On hearing all the evidence, the jury deliberated and convicted Markhasev of murder.

Bill Cosby and his son Ennis Cosby. Courtesy Andrea Mohin, The New York Times

371

TRACE EVIDENCE I

• The follicular tag, a translucent piece of tissue surrounding the hair’s shaft near the root, is a rich source of DNA associated with hair. Mitochondrial DNA can also be extracted from the hair shaft.

• All positive microscopic hair comparisons must be confi rmed by DNA analysis.

Forensic Examination of Fibers Just as hair left at a crime scene can be used for identifi cation, so can the fi bers that compose fabrics and garments. Fibers may become important evidence in incidents that involve personal contact—such as homicide, assault, and sexual offenses—in which cross-transfers may occur between the clothing of suspect and victim. Similarly, the force of impact between a hit-and-run victim and a vehicle often leaves fi bers, threads, or even whole pieces of clothing adhering to parts of the vehicle. Fibers may also become fi xed in screens or on glass that is broken in the course of a breaking-and-entering attempt.

Regardless of where and under what conditions fi bers are recovered, their ultimate value as forensic evidence depends on the criminalist’s ability to nar- row their origin to a limited number of sources or even to a single source. Unfortunately, mass production of garments and fabrics has limited the value of fi ber evidence in this respect, and only rarely do fi bers recovered at a crime scene provide individual identifi cation with a high degree of certainty.

TYPES OF FIBERS

For centuries, humans depended on fi bers derived from natural sources such as plants and animals. However, early in the twentieth century, the fi rst manu- factured fi ber—rayon—became a practical reality, followed in the 1920s by the

introduction of cellulose acetate. Since the late 1930s, scientists have pro- duced dozens of new fi bers. In fact, there have been greater advances in the development of fi bers, fabrics, fi nishes, and other textile-processing techniques since 1900 than in the preceding fi ve thousand years of re- corded history. Today, such varied items as clothing, carpeting, drapes, wigs, and even artifi cial turf attest to the predominant role that manu- factured fi bers have come to play in our culture and environment. When discussing forensic examination of fi bers, it is convenient to classify them into two broad groups: natural and manufactured.

NATURAL FIBERS Natural fi bers are wholly derived from animal or plant sources. Natural fi bers encountered in crime laboratory examina- tions come primarily from animals. These include hair coverings from such animals as sheep (wool), goats (mohair, cashmere), camels, llamas, alpacas, and vicuñas. Fur fi bers include those obtained from animals such as mink, rabbit, beaver, and muskrat.

The forensic examination of animal fi bers uses the same procedures discussed in the previous section for the forensic examination of animal hairs. The identifi cation and comparison of such fi bers relies solely on a mi- croscopic examination of color and morphological characteristics. Again, a suffi cient number of standard/reference specimens must be examined to establish the range of fi ber characteristics that make up the suspect fabric.

By far the most prevalent plant fi ber is cotton. The wide use of undyed white cotton fi bers in clothing and other fabrics has made its evidential value almost meaningless, but the presence of dyed cotton in a combina- tion of colors has, in some cases, enhanced its evidential signifi cance.

natural fi bers Fibers derived entirely from animal or plant sources.

FIGURE 9 Photomicrograph of cottonfi - ber (450�).

372

TRACE EVIDENCE I

The microscopic view of cotton fi ber shown in Figure 9 reveals its most distin- guishing feature—its ribbonlike shape with twists at irregular intervals.

MANUFACTURED FIBERS Beginning with the introduction of rayon in 1911 and the development of nylon in 1939, manufactured fi bers have increasingly replaced natural fi bers in garments and fabrics. Such fi bers are marketed un- der hundreds of trade names. To reduce consumer confusion, the US Federal Trade Commission has approved “generic” or family names for the grouping of all manufactured fi bers. Many of these generic classes are produced by several manufacturers and are sold under a confusing variety of trade names. For example, in the United States, polyesters are marketed under names that include Dacron, Fortrel, and Kodel. In England, polyesters are called Terylene. Table 1 lists major generic fi bers, along with common trade names and their characteristics and applications.

The fi rst machine-made fi bers were manufactured from raw materials derived from cotton or wood pulp, and these are still being made. The raw materials are processed, and pure cellulose is extracted from them. Depend- ing on the type of fi ber desired, the cellulose may be chemically treated and dissolved in an appropriate solvent before it is forced through the small holes of a spinning jet, or spinneret, to produce the fi ber. Fibers manufactured from natural raw materials in this manner are classifi ed as regenerated fi bers and commonly include rayon, acetate, and triacetate, all of which are produced from regenerated cellulose.

Most of the fi bers currently manufactured are produced solely from syn- thetic chemicals and are therefore classifi ed as synthetic fi bers. These include nylons, polyesters, and acrylics. The creation of synthetic fi bers became a re- ality only when scientists developed a method of synthesizing long-chained molecules called polymers.

In 1930, chemists discovered an unusual characteristic of one of the poly- mers under investigation. When a glass rod in contact with viscous material in a beaker was slowly pulled away, the substance adhered to the rod and formed a fi ne fi lament that hardened as soon as it entered the cool air. Fur- thermore, the cold fi laments could be stretched several times their extended length to produce a fl exible, strong, and attractive fi ber. This fi rst synthetic fi ber was improved and then marketed as nylon. Since then, fi ber chemists have successfully synthesized new polymers and have developed more effi - cient methods for manufacturing them. These efforts have produced a multi- tude of synthetic fi bers.

IDENTIFICATION AND COMPARISON

OF MANUFACTURED FIBERS

The evidential value of fi bers lies in the criminalist’s ability to trace their ori- gin. Obviously, if the examiner is presented with fabrics that can be exactly fi tted together at their torn edges, the fabrics must be of common origin.

More often, however, the criminalist obtains a limited number of fi bers for identifi cation and comparison. Generally, in these situations obtaining a physical match is unlikely, and the examiner must resort to a side-by-side comparison of the standard/reference and crime-scene fi bers.

MICROSCOPIC EXAMINATION OF FIBERS The fi rst and most important step in the examination is a microscopic comparison for color and diameter using a comparison microscope. Unless these two characteristics agree, there is little reason to suspect a match. Other morphological features that may aid in the  comparison are lengthwise striations (lined markings) on the surface of some fi bers and the pitting of the fi ber’s surface with delustering particles

manufactured fi bers Fibers derived from either natural or synthetic polymers.

373

TRACE EVIDENCE I

TABLE 1 Major Generic Fibers MAJOR GENERIC FIBER CHARACTERISTICS MAJOR DOMESTIC AND INDUSTRIAL USES

Acetate • Luxurious feel and appearance • Wide range of colors and lusters • Excellent drapability and softness • Relatively fast-drying • Shrink-, moth-, and mildew-resistant

Apparel: Blouses, dresses, foundation garments, lingerie, linings, shirts, slacks, sportswear Fabrics: Brocade, crepe, double knits, faille, knitted jerseys, lace, satin, taffeta, tricot Home Furnishings: Draperies, upholstery Other: Cigarette fi lters, fi berfi ll for pillows, quilted products

Acrylic • Soft and warm • Wool-like • Retains shape • Resilient • Quick-drying • Resistant to moths, sunlight, oil,

and chemicals

Apparel: Dresses, infant wear, knitted garments, skiwear, socks, sportswear, sweaters Fabrics: Fleece and pile fabrics, face fabrics in bonded fabrics, simulated furs, jerseys Home Furnishings: Blankets, carpets, draperies, upholstery Other: Auto tops, awnings, hand-knitting and craft yarns, industrial and geotextile fabrics

Aramid • Does not melt • Highly fl ame-resistant • Great strength • Great resistance to stretch • Maintains shape and form at high

temperatures

Hot-gas fi ltration fabrics, protective clothing, military helmets, protective vests, structural composites for aircraft and boats, sailcloth, tires, ropes and cables, mechanical rubber goods, marine and sporting goods

Bicomponent • Thermal bonding • Self-bulking • Very fi ne fi bers • Unique cross-sections • The functionality of special polymers

or additives at reduced cost

Uniform distribution of adhesive; fi ber remains a part of structure and adds integrity; customized sheath materials to bond various materials; wide range of bonding temperatures; cleaner, environmentally friendly (no effl uent); recyclable; lamination/molding/densifi cation of composites

Lyocell • Soft, strong, absorbent • Good dyeability • Fibrillates during wet processing

to produce special textures

Dresses, slacks, and coats

Melamine • White and dyeable • Flame resistance and low thermal

conductivity • High-heat dimensional stability • Processable on standard textile

equipment

Fire-Blocking Fabrics: Aircraft seating, fi re blockers for upholstered furniture in high-risk occupancies (e.g., to meet California TB 133 requirements) Protective Clothing: Firefi ghters’ turnout gear, insulating thermal liners, knit hoods, molten metal splash apparel, heat-resistant gloves Filter Media: High-capacity, high-effi ciency, high-temperature baghouse air fi lters

Modacrylic • Soft • Resilient • Abrasion- and fl ame-resistant • Quick-drying • Resists acids and alkalies • Retains shape

Apparel: Deep-pile coats, trims, linings, simulated fur, wigs and hairpieces Fabrics: Fleece fabrics, industrial fabrics, knit-pile fabric backings, nonwoven fabrics Home Furnishings: Awnings, blankets, carpets, fl ame-resistant draperies and curtains, scatter rugs Other: Filters, paint rollers, stuffed toys

374

TRACE EVIDENCE I

MAJOR GENERIC FIBER CHARACTERISTICS MAJOR DOMESTIC AND INDUSTRIAL USES

Nylon • Exceptionally strong • Supple • Abrasion-resistant • Lustrous • Easy to wash • Resists damage from oil and many

chemicals • Resilient • Low in moisture absorbency

Apparel: Blouses, dresses, foundation garments, hosiery, lingerie and underwear, raincoats, ski and snow apparel, suits, windbreakers Home Furnishings: Bedspreads, carpets, draperies, curtains, upholstery Other: Air hoses, conveyor and seat belts, parachutes, racket strings, ropes and nets, sleeping bags, tarpaulins, tents, thread, tire cord, geotextiles

Olefi n • Unique wicking properties that make it very comfortable

• Abrasion-resistant • Quick-drying • Resistant to deterioration from

chemicals, mildew, perspiration, rot, and weather

• Sensitive to heat • Soil-resistant • Strong; very lightweight • Excellent colorfastness

Apparel: Pantyhose, underwear, knitted sports shirts, men’s half-hose, men’s knitted sportswear, sweaters Home Furnishings: Carpet and carpet backing, slipcovers, upholstery Other: Dye nets, fi lter fabrics, laundry bags, sandbags, geotextiles, automotive interiors, cordage, doll hair, industrial sewing thread

Polyester • Strong • Resistant to stretching and shrinking • Resistant to most chemicals • Quick-drying • Crisp and resilient when wet or dry • Wrinkle- and abrasion-resistant • Retains heat-set pleats and creases • Easy to wash

Apparel: Blouses, shirts, career apparel, children’s wear, dresses, half-hose, insulated garments, ties, lingerie and underwear, permanent press garments, slacks, suits Home Furnishings: Carpets, curtains, draperies, sheets and pillowcases Other: Fiberfi ll for various products, fi re hoses, power belting, ropes and nets, tire cord, sail, V-belts

PBI • Extremely fl ame-resistant • Outstanding comfort factor combined

with thermal and chemical stability properties

• Will not burn or melt • Low shrinkage when exposed to fl ame

Suitable for high-performance protective apparel such as fi refi ghters’ turnout coats, astronaut space suits, and applications in which fi re resistance is important

Rayon • Highly absorbent • Soft and comfortable • Easy to dye • Versatile • Good drapability

Apparel: Blouses, coats, dresses, jackets, lingerie, linings, millinery, rainwear, slacks, sports shirts, sportswear, suits, ties, work clothes Home Furnishings: Bedspreads, blankets, carpets, curtains, draperies, sheets, slipcovers, tablecloths, upholstery Other: Industrial products, medical-surgical products, nonwoven products, tire cord

Spandex • Can be stretched 500 percent without breaking

• Can be stretched repeatedly and recover original length

• Lightweight • Stronger and more durable than rubber • Resistant to body oils

Apparel (articles in which stretch is desired): Athletic apparel, bathing suits, delicate laces, foundation garments, golf jackets, ski pants, slacks, support and surgical hose

Source: American Fiber Manufacturers Assoc. Inc., Washington, DC, www.fi ngersource.com Reprinted by permission.

375

TRACE EVIDENCE I

(usually titanium dioxide) added in the manufacturing process to reduce shine (see Figure 10 ).

The cross-sectional shape of a fi ber may also help characterize the fi ber (see Figure 11 ). 5 In the early 1880s, Wayne Williams was charged and tried for the murder of two individuals in the Atlanta, Georgia, region. During the eight-week trial, evidence linking Williams to those murders and to the murder of ten other individuals was introduced. An essential part of the gov- ernment’s case was the numerous fi bers linking Williams to the murders. Unusually shaped yellow-green fi bers discovered on a number of the murder victims were linked to a carpet in the Williams home. This fi ber was a key

FIGURE 10 Photomicrographs of synthetic fi bers: (a) cellulose triacetate (450�) and (b) olefi n fi ber embedded with titanium dioxide particles (450�).

Round

Dumbbell Flat

Multi-lobed

Trilobal

FIGURE 11 Cross-sectional shapes of fi bers.

376

TRACE EVIDENCE I

element in proving Williams’s guilt. A photomicrograph of this unusually shaped fi ber is shown in Figure 12 .

Although two fi bers may seem to have the same color when viewed un- der the microscope, compositional differences may actually exist in the dyes that were applied to them during their manufacture. In fact, most textile fi bers are impregnated with a mixture of dyes selected to obtain a desired shade or color. The signifi cance of a fi ber comparison is enhanced when the forensic examiner can show that the questioned and standard/reference fi bers have the same dye composition.

ANALYTICAL TECHNIQUES USED IN FIBER EXAMINATION Chemists can use selective absorption of light by materials to characterize them. In particular, light in the ultraviolet, visible, and infrared regions of the electromagnetic spectrum is most helpful for this purpose. Unfortunately, in the past, forensic chemists were unable to take full advantage of the capabilities of spectropho- tometry for examining trace evidence because most spectrophotometers are not well suited for examining the very small particles frequently encountered as evidence. Recently, linking the microscope to a computerized spectropho- tometer has added a new dimension to its capability. This combination has given rise to a new instrument called the microspectrophotometer. In many respects, this is an ideal marriage from the forensic scientist’s viewpoint.

The visible-light microspectrophotometer is a convenient way for ana- lysts to compare the colors of fibers through spectral patterns. This tech- nique is not limited by sample size; a fiber as small as 1 millimeter long or less can be examined by this type of microscope. The examination is non- destructive and is carried out on fibers simply mounted on a microscope slide.

CHEMICAL COMPOSITION Before the forensic scientist can reach a conclu- sion that two or more fi bers compare, it must be shown that the fi bers in ques- tion have the same chemical composition. In this respect, tests are performed to confi rm that all of the fi bers involved belong to the same broad generic class. Additionally, the comparison will be substantially enhanced if it can be demonstrated that all of the fi bers belong to the same subclassifi cation within their generic class. For example, at least four types of nylon are available in commercial and consumer markets, including nylon 6, nylon 6-10, nylon 11, and nylon 6-6. Although all types of nylon have many properties in common,

FIGURE 12 A scanning electron photomicrograph of the cross-section of a nylon fi ber removed from a sheet used to transport the body of a murder victim. The fi ber, associated with a carpet in Wayne Williams’s home, was manufactured in 1971 in relatively small quantities. Courtesy Federal Bureau of Investigation, Washington, DC

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each may differ in physical shape, appearance, and dyeability because of mod- ifi cations in their basic chemical structure.

Textile chemists have devised numerous tests for determining the class of a fi ber. However, unlike the textile chemist, the criminalist frequently does not have the luxury of a substantial quantity of the fabric to work with and must therefore select tests that will yield the most information with the least amount of material. Only a single fi ber may be available for analysis, and often this may amount to no more than a minute strand recovered, for example, from a fi ngernail scraping from a homicide or rape victim.

INFRARED ABSORPTION The polymers that compose a manufactured fi ber, like any organic substance, selectively absorb infrared light in a characteristic pattern. Infrared spectrophotometry thus provides a rapid and reliable method for identifying the generic class, and in some cases the subclass, of a fi ber. The infrared microspectrophotometer combines a microscope with an infrared spectrophotometer. Such a combination makes possible the infrared analysis of a small, single-strand fi ber while it is being viewed under a microscope.

SIGNIFICANCE OF FIBER EVIDENCE

Once a fi ber match has been determined, the question of the signifi cance of such a fi nding is bound to be raised. In reality, no analytical technique permits the criminalist to link a fi ber strand defi nitively to any single garment.

CLOSER ANALYSIS THE MICROSPECTROPHOTOMETER

With the development of the microspectrophotometer, a forensic analyst can view a particle under a microscope while a beam of light is directed at the particle to obtain its absorption spectrum. Depend- ing on the type of light employed, an examiner can acquire either

a visible or an infrared (IR) spectral pattern of the substance being viewed under the microscope. The obvious advantage of this ap- proach is that it provides added information to characterize trace quantities of evidence. A microspectrophotometer designed to mea- sure the uptake of visible light by materials is shown here.

Visual comparison of color is usually one of the fi rst steps in examining paint, fi ber, and ink evidence. Such comparisons are eas- ily obtained using a comparison microscope. A forensic scientist can use the microspectrophotometer to compare the color of materials visually while plotting an absorption spectrum for each item under examination. This displays the exact wavelengths at which each item absorbs in the visible-light spectrum. Occasionally, colors that ap- pear similar by visual examination show signifi cant differences in their absorption spectra.

Another emerging technique in forensic science is the use of the IR microspectrophotometer to examine fi bers and paints. The “fi ngerprint” IR spectrum (see Figure 1 and 2 in the Case File on page 338) is unique for each chemical substance. Therefore, obtain- ing such a spectrum from either a fi ber or a paint chip allows the analyst to better identify and compare the type of chemicals from which these materials are manufactured. With a microspectropho- tometer, a forensic analyst can view a substance through the micro- scope and at the same time have the instrument plot the infrared absorption spectrum for that material.

A visible-light microspectrophotometer. Courtesy CRAIC Technologies Inc., Altadena, CA, www.microspectra.com

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TRACE EVIDENCE I

Furthermore, except in the most unusual circumstances, no statistical data- bases are available for determining the probability of a fi ber’s origin. Consid- ering the mass distribution of synthetic fi bers and the constantly changing fashion tastes of our society, it is highly unlikely that such data will be available in the foreseeable future.

Despite these limitations, an investigator should not discount or mini- mize the signifi cance of a fi ber association. An enormous variety of fi bers exists in our society. By simply looking at the random individuals we meet every day, we can see how unlikely it is to fi nd two people wearing identically colored fabrics (with the exception of blue denims or white cottons). There are thousands of different-colored fi bers in our environment. Combine this with the fact that forensic scientists compare not only the color of fi bers but also their size, shape, microscopic appearance, chemical composition, and dye content, and one can now begin to appreciate how unlikely it is to fi nd two indistinguishable colored fi bers on two randomly selected sources.

Furthermore, the signifi cance of a fi ber association increases dramati- cally when the analyst can link two or more distinctly different fi bers to the same object. Likewise, the associative value of fi ber evidence is dramatically enhanced if it is accompanied by other types of physical evidence linking a person or object to a crime. As with most class evidence, the signifi cance of a fi ber comparison is dictated by the circumstances of the case; by the location, number, and nature of the fi bers examined; and, most important, by the judg- ment of an experienced examiner.

Collection and Preservation of Fiber Evidence As criminal investigators have become more aware of the potential contribution of trace physical evidence to the success of their investigations, they have placed greater emphasis on conducting thorough crime-scene searches for evidence of forensic value. Their skill and determination at carrying out these tasks is tested in the collection of fi ber-related evidence. Fiber evidence can be associated with virtually any type of crime. It usually cannot be seen with the naked eye and thus can be easily overlooked by someone not specifi cally searching for it.

An investigator committed to optimizing the laboratory’s chances for lo- cating minute strands of fi bers identifi es and preserves potential “carriers” of fi ber evidence. Relevant articles of clothing should be packaged carefully in paper bags. Each article must be placed in a separate bag to avoid cross- contamination of evidence. Scrupulous care must be taken to prevent articles of clothing from different people or from different locations from coming into contact. Such articles must not even be placed on the same surface prior to packaging. Likewise, carpets, rugs, and bedding are to be folded carefully to protect areas suspected of containing fi bers. Car seats should be carefully covered with polyethylene sheets to protect fi ber evidence, and knife blades should be covered to protect adhering fi bers. If a body is thought to have been wrapped at one time in a blanket or carpet, adhesive tape lifts of exposed body areas may reveal fi ber strands.

Occasionally the fi eld investigator may need to remove a fi ber from an object, particularly if loosely adhering fi brous material may be lost in transit to the laboratory. These fi bers must be removed with a clean forceps and placed in a small sheet of paper, which, after folding and labeling, should be placed in- side another container. Again, scrupulous care must be taken to prevent con- tact between fi bers collected from different objects or from different locations.

In the laboratory, the search for fi ber evidence on clothing and other rel- evant objects, as well as in debris, is time consuming and tedious and will test the skill and patience of the examiner. The crime-scene investigator can

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Dr. Jeffrey MacDonald, pictured here, was convicted in 1979 of mur- dering his wife and two young daughters. The events surrounding the crime and the subsequent trial were recounted in Joe McGinniss’s best-selling book Fatal Vision . The focus of Dr. MacDonald’s defense was that intruders entered his home and committed these violent acts. Eleven years after this conviction, Dr. MacDonald’s attorneys fi led a pe- tition for a new trial, claiming the existence of “critical” new evidence.

The defense asserted that wig fi bers found on a hairbrush in the MacDonald residence were evidence that an intruder dressed in a

wig entered the MacDon- ald home on the day of the murder. Subsequent examination of this claim by the FBI Laboratory fo- cused on a blond fall (a type of artifi cial hair ex- tension) frequently worn by Dr.  MacDonald’s wife. Fibers removed from the fall were shown to clearly match fi bers on

the hairbrush. The examination included the use of infrared micro- spectrophotometry to demonstrate that the suspect wig fi bers were chemically identical to fi bers found in the composition of Mrs. Mac- Donald’s fall (see Figure 1 ). Hence, although wig fi bers were found at the crime scene, the source of these fi bers could be accounted for: Mrs.  MacDonald’s fall.

Another piece of evidence cited by Dr. MacDonald’s lawyers was a bluish-black woolen fi ber found on the body of Mrs. MacDonald. They claimed that this fi ber compared to a bluish-black woolen fi ber recov- ered from the club used to assault her. These wool fi bers were central to Dr. MacDonald’s defense that the “intruders” wore dark-colored cloth- ing. Initial examination showed that the fi bers were microscopically indistinguishable. However, the FBI also compared the two wool fi bers by visible-light microspectrophotometry. Comparison of their spectra clearly showed that their dye compositions differed, providing no evi- dence of outside intruders (see Figure 2 ). Ultimately, the US Supreme Court denied the merits of Jeffrey MacDonald’s petition for a new trial.

Source: Based on information contained in B. M. Murtagh and M. P. Malone, “Fatal Vision Revisited,” Police Chief (June 1993): 15. Jeffrey MacDonald in 1995 at Sheridan,

Oregon, Federal Correctional Institution. Courtesy AP Wide World Photos

CASE FILES FATAL VISION REVISITED

K47 (Mrs. MacDonald’s fall)

Ab so

rb an

ce

Q48 (fiber from hairbrush)

2.5 3.0 3.5 4.0 4.5 5.0 6.0 8 10 Microns

4000 3500 3000 2500 2000 1500 1000 Wavenumber

FIGURE 1 A fi ber comparison made with an infrared spectrophotometer. The infrared spectrum of a fi ber from Mrs. MacDonald’s fall compares to a fi ber recovered from a hairbrush in the MacDonald home. These fi bers were identifi ed as modacrylics, the most common type of synthetic fi ber used in the manufacture of human hair goods. Courtesy SA Michael Malone, FBI Laboratory, Washington, DC

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manage this task by collecting only relevant items for examination—pinpointing areas where a likely transfer of fi ber evidence occurred and then ensuring the proper collection and preservation of these materials.

Quick Review • Fibers may be classifi ed into two broad groups: natural and manufactured. • Most fi bers currently manufactured are produced solely from synthetic

chemicals and are therefore classifi ed as synthetic fi bers . They include nylons, polyesters, and acrylics.

• Microscopic comparisons between questioned and standard/reference fi - bers are initially undertaken for color and diameter characteristics. Other features that could be important in comparing fi bers are striations on the surface of the fi ber, the presence of delustering particles, and the cross- sectional shape of the fi ber.

• Using a visible-light microspectrophotometer is a convenient way for ana- lysts to compare the colors of fi bers through spectral patterns.

• Infrared microspectrophotometry is a reliable method for identifying the chemical composition of fi bers.

• Fiber evidence collected at each location should be placed in separate containers to avoid cross-contamination. Care must be taken to prevent articles of clothing from different people or from different locations from coming into contact with each other.

400 500 600 Wavelength (nanometers)

% T

ra ns

m is

si on

700 800

Q89 (wool fiber from club)

Q88 (wool fiber from Mrs. MacDonald’s

bicep)

FIGURE 2 The visible-light spectrum for the woolen fi ber recovered from Mrs. MacDonald’s body is clearly different from that of the fi ber recovered from the club used to assault her. Courtesy SA Michael Malone, FBI Laboratory, Washington, DC

VIRTUAL LAB Forensic Hair Analysis To perform a virtual forensic hair analysis, go to www .pearsoncustom.com/us/vlm/

VIRTUAL LAB Examination of Textile Fibers by Microscopy To perform a virtual fi ber examination lab, go to www .pearsoncustom.com/us/vlm/

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