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Criminalistics An Introduction to Forensic Science

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Richard Saferstein, Ph.D. Forensic Science Consultant, Mt. Laurel, New Jersey Lecturer, Widener University School of Law

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Library of Congress Cataloging-in-Publication Data Saferstein, Richard

Criminalistics : an introduction to forensic science / Richard Saferstein.—10th ed. p. cm.

Includes bibliographical references and index. ISBN-13: 978-0-13-504520-6 ISBN-10: 0-13-504520-7

1. Criminal investigation. 2. Forensic ballistics. 3. Chemistry, Forensic. 4. Medical jurisprudence. I. Title. HV8073.S24 2011 363.25—dc22

2009042128

ISBN 10: 0-13-504520-7 ISBN 13: 978-0-13-504520-6

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Ted Bundy, Serial Killer

The name Ted Bundy is synonymous with the term serial killer. This handsome, gregarious, and worldly onetime law student is believed to be responsible for forty murders between 1964 and 1978. His reign of terror stretched from the Pacific Northwest down into California and into Utah, Idaho, and Colorado, finally ending in Florida. His victims were typically young women, usually murdered with a blunt instrument or by strangulation and sexually assaulted before and after death. First convicted in Utah in 1976 on a charge of kidnapping, Bundy managed to escape after his extradition to Colorado on a murder charge. Ultimately, Bundy found his way to the Tallahassee area of Florida. There he unleashed mayhem, killing two women at a Florida State University sorority house and then murdering a 12-year-old girl three weeks later. Fortunately, future

victims were spared when Bundy was arrested while driving a stolen vehicle. As police

investigated the sorority murders, they noted that one victim, who had been beaten over the head with a log, raped, and strangled, also had bite

marks on her left buttock and breast. Supremely confident that he could beat the sorority murder charges, the arrogant Bundy insisted on

acting as his own attorney. His unfounded optimism was shattered in the courtroom when a forensic odontologist matched the bite mark on the victim’s buttock to Bundy’s front teeth. Bundy was ultimately executed in 1989.

headline news

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After studying this chapter you should be able to: • Define and distinguish forensic science and criminalistics

• 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 scientific evidence in the courtroom

• Explain the role and responsibilities of the expert witness

• Understand what specialized forensic services, aside from the crime laboratory, are generally available to law enforcement personnel

Introduction

expert witness Locard’s exchange

principle scientific method

KEY TERMS

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4 CHAPTER 1

Definition and Scope of Forensic Science Forensic science, in its broadest definition, 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 definition and enforcement of such laws.

Each year, as government finds it increasingly necessary to regulate the activities that most intimately influence our daily lives, science merges more closely with civil and criminal law. Consider, for example, the laws and agencies 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 difficult to conceive of any food and drug regulation or environmental protection act that could be effectively monitored and enforced without the assistance of scientific technology and the skill of the scientific community.

Laws are continually being broadened and revised to counter the alarming 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 scientific community for advice and technical support for their efforts. Can the tech- nology that put astronauts on the moon, split the atom, and eradicated most dreaded diseases be enlisted in this critical battle? Unfortunately, science cannot offer final and authoritative solutions to problems that stem from a maze of social and psychological factors. However, as the contents of this book will attest, science does occupy 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 that reflects the events that have occurred at a crime. It will also become apparent to the reader that a good deal of work remains to be done if the full potential of science as applied to criminal investigations is to be realized.

Considering the vast array of civil and criminal laws that regulate society, forensic science, in its broadest sense, has become so comprehensive a subject as to make a meaningful introduc- tory textbook treatment of its role and techniques most difficult, if not overwhelming. For this reason, we must find practical limits that narrow the scope of the subject. Fortunately, common usage provides us with such a limited definition: 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 professions that use their skills to help law enforcement officials conduct 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 Sciences 4. General 5. Jurisprudence 6. Odontology 7. Pathology/Biology 8. Physical Anthropology 9. Psychiatry/Behavioral Sciences

10. Questioned Documents 11. Toxicology

Even within the limited definition just presented, we will restrict our discussion in this book to the areas of chemistry, biology, physics, geology, and computer technology, which are useful for determining the evidential value of crime-scene and related evidence, omitting any references to medicine and law. Forensic pathology, psychology, anthropology, and odontology encompass important and relevant areas of knowledge and practice in law enforcement, each being an integral part of the total forensic science service that is provided to any up-to-date crim- inal justice system. However, except for brief discussions, these subjects go beyond the intended range of this book, and the reader is referred elsewhere for discussions of their applications and

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INTRODUCTION 5

techniques.1 Instead, we will attempt to focus on the services of what has popularly become known as the crime laboratory, where the principles and techniques of the physical and natural sciences are practiced and applied to the analysis of crime-scene evidence.

For many, the term criminalistics seems more descriptive than forensic science for describ- ing the services of a crime laboratory. The two terms will be used interchangeably in this text. Regardless of title—criminalist or forensic scientist—the trend of events has made the scientist in the crime laboratory an active participant in the criminal justice system.

Primetime television shows like CSI: Crime Scene Investigation have greatly increased the public’s awareness of the use of science in criminal and civil investigations. However, by simpli- fying scientific procedures to fit into the available airtime, these shows have created unrealistic expectations of forensic science skills within both the public and the legal community. In these shows, members of the CSI team collect evidence at the crime scene, process all evidence, ques- tion witnesses, interrogate suspects, carry out search warrants, and testify in court. In the real world, these tasks are almost always delegated to different people in different parts of the crimi- nal justice system. Procedures that could take days, weeks, months, or years in reality appear on these shows to take mere minutes. This false image is especially relevant to the pub- lic’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 produces unrealistic expec- tations that a prosecutor’s case should always be bolstered and supported by foren- sic 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 first to the individuals who developed the princi- ples 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.

Literary Roots Today many believe that Sir Arthur Conan Doyle had a considerable influence on popularizing scientific crime-detection methods through his fictional character Sherlock Holmes (see Figure 1–1), who first applied the newly developing princi- ples of serology (see Chapter 10), fingerprinting, firearms identification, and questioned-document examination long before their value was first 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 first Sherlock Holmes novel, A Study in Scarlet, published in 1887, we find ex- amples of Doyle’s uncanny ability to describe scientific methods of detection years before they were actually discovered and implemented. For instance, here Holmes probes and recognizes the potential usefulness of forensic serology to criminal investigation:

“I’ve found it. I’ve found it,” he shouted to my companion, running towards us with a test tube in his hand. “I have found a reagent which is precipitated by hemoglobin 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.

1 Two excellent references are André A. Moenssens, Fred E. Inbau, James Starrs, and Carol E. Henderson, Scientific Ev- idence in Civil and Criminal Cases, 4th ed. (Mineola, N.Y.: Foundation Press, 1995); and Werner U. Spitz, ed., Medicolegal Investigation of Death, 4th ed. (Springfield, Ill.: Charles C. Thomas, 2006).

FIGURE 1–1 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 police. © Paul C. Chauncey/CORBIS. All rights reserved.

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So is the microscopic examination 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 hinging 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 difficulty.”

Important Contributors to Forensic Science Many people can be cited for their specific contributions to the field of forensic science. The following is just a brief list of those who made the earliest contributions to formulating the disci- plines that now constitute forensic science.

MATHIEU ORFILA (1787–1853) Orfila is considered the father of forensic toxicology. A native of Spain, he ultimately became a renowned teacher of medicine in France. In 1814, Orfila published the first scientific treatise on the detection of poisons and their effects on animals. This treatise established forensic toxicology as a legitimate scientific endeavor.

ALPHONSE BERTILLON (1853–1914) Bertillon devised the first scientific system of personal identification. In 1879, Bertillon began to develop the science of anthropometry (see Chapter 16), a systematic procedure of taking a series of body measurements as a means of distinguishing one individual from another. (See Figure 1–2.) For nearly two decades, this system was considered the most accurate method of personal identification. Although anthropometry was eventually replaced by fingerprinting in the early 1900s, Bertillon’s early efforts have earned him the dis- tinction of being known as the father of criminal identification.

FRANCIS GALTON (1822–1911) Galton undertook the first definitive study of fingerprints and developed a methodology of classifying them for filing. In 1892, he published a book titled Finger Prints, which contained the first statistical proof supporting the uniqueness of his method of personal identification. His work went on to describe the basic principles that form the present system of identification by fingerprints.

LEONE LATTES (1887–1954) In 1901, Dr. Karl Landsteiner discovered that blood can be grouped into different categories. These blood groups or types are now recognized as A, B, AB, and O. The possibility that blood grouping could be a useful characteristic for the identification of an indi- vidual intrigued Dr. Lattes, a professor at the Institute of Forensic Medicine at the University of Turin in Italy. In 1915, he devised a relatively simple procedure for determining the blood group of a dried bloodstain, a technique that he immediately applied to criminal investigations.

CALVIN GODDARD (1891–1955) To determine whether a particular gun has fired a bullet requires a comparison of the bullet with one that has been test-fired from the suspect’s weapon. Goddard, a U.S. Army colonel, refined the techniques of such an examination by using the comparison microscope. Goddard’s expertise established the comparison microscope as the indispensable tool of the modern firearms examiner.

ALBERT S. OSBORN (1858–1946) Osborn’s development of the fundamental principles of document examination was responsible for the acceptance of documents as scientific evidence by the courts. In 1910, Osborn authored the first significant text in this field, Questioned Documents. This book is still considered a primary reference for document examiners.

WALTER C. McCRONE (1916–2002) Dr. McCrone’s career paralleled startling advances in sophisticated analytical technology. Nevertheless, during his lifetime McCrone became the world’s preeminent microscopist. Through his books, journal publications, and research institute, McCrone was a tireless advocate for applying microscopy to analytical problems, particularly

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FIGURE 1–2 Bertillon’s system of bodily measurements as used for the identification of an individual. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com

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Locard’s exchange principle Whenever two objects come into contact with one another, there is exchange of materials between them

8 CHAPTER 1

forensic science cases. McCrone’s exceptional communication skills made him a much-sought- after instructor, and he was responsible for educating thousands of forensic scientists throughout the world in the application of microscopic techniques. Dr. McCrone used microscopy, often in conjunction with other analytical methodologies, to examine evidence in thousands of criminal and civil cases throughout a long and illustrious career.

HANS GROSS (1847–1915) Gross wrote the first treatise describing the application of scientific disciplines to the field of criminal investigation in 1893. A public prosecutor and judge in Graz, Austria, Gross spent many years studying and developing principles of criminal investigation. In his classic book Handbuch für Untersuchungsrichter als System der Kriminalistik (later pub- lished in English under the title Criminal Investigation), he detailed the assistance that investiga- tors could expect from the fields of microscopy, chemistry, physics, mineralogy, zoology, botany, anthropometry, and fingerprinting. He later introduced the forensic journal Archiv für Kriminal Anthropologie und Kriminalistik, which still serves as a medium for reporting improved methods of scientific crime detection.

EDMOND LOCARD (1877–1966) Although Gross was a strong advocate of the use of the sci- entific method in criminal investigation, he did not make any specific technical contributions to this philosophy. Locard, a Frenchman, 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 first years of work, the only available instruments were a microscope and a rudimentary spectrometer. However, his enthusiasm quickly overcame the technical and mone- tary deficiencies he encountered. From these modest beginnings, Locard’s research and accom- plishments became known throughout the world by forensic scientists and criminal investigators. Eventually he became the founder and director of the Institute of Criminalistics at the University of Lyons; this quickly developed into a leading international center for study and research in forensic science.

Locard believed that when a person comes in contact with an object or person, a cross- transfer of materials occurs (Locard’s exchange principle). Locard maintained that every criminal can be connected to a crime by dust particles carried from the crime scene. This concept was reinforced by a series of successful 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 particles and coins were composed of exactly the same metallic elements. Confronted with this evidence, the suspects were arrested and soon confessed to the crime. After World War I, Locard’s successes served as an impetus for the formation of police laboratories in Vienna, Berlin, Sweden, Finland, and Holland.

Crime Laboratories The most ambitious commitment to forensic science occurred in the United States with the sys- tematic development of national and state crime laboratories. This development greatly hastened the progress of forensic science.

Crime Labs in the United States In 1932, the Federal Bureau of Investigation (FBI), under the directorship of J. Edgar Hoover, organized a national laboratory that offered forensic services to all law enforcement agencies in the country. During its formative stages, agents consulted extensively with business executives, manufacturers, and scientists whose knowledge and experience were useful in guiding 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. 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 first time, a facility dedicated to conducting research to develop

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new and reliable scientific 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.

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 first U.S. university institute for criminology and criminalistics at the University of California at Berkeley. However, this institute lacked any official status in the university until 1948, when a school of criminology was formed. The famous criminalist Paul Kirk (see Figure 1–3) was selected to head its criminalistics department. Many graduates of this school have gone on to help develop forensic laboratories in other parts of the state and country.

California has numerous federal, state, county, and city crime laboratories, many of which op- erate independently. However, in 1972 the California Department of Justice embarked on an ambi- tious plan to create a network of state-operated crime laboratories.As a result, California has created a model system of integrated forensic laboratories consisting of regional and satellite facilities. An informal exchange of information and expertise is facilitated among California’s criminalist com- munity through a regional professional society, the California Association of Criminalists. This or- ganization was 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.

International Crime Labs In contrast to the American system of independent local laboratories, Great Britain has developed a national system of regional laboratories under the direction of the government’s Home Office. England and Wales are serviced by six regional laboratories, including the Metropolitan Police Laboratory (established in 1935), which services London. In the early 1990s, the British Home Office reorganized the country’s forensic laboratories into the Forensic Science Service and in- stituted a system in which police agencies are charged a fee for services rendered by the labora- tory. The fees are based on “products,” or a set of examinations that are packaged together and designed to be suitable for particular types of physical evidence. 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. One such organization, LGC in the United Kingdom, employs more than one thousand forensic scientists.

In Canada, forensic services are provided by three government-funded institutes: (1) six 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 a hundred countries throughout the world have at least one laboratory facility offering services in the field of forensic science.

INTRODUCTION 9

FIGURE 1–3 Paul Leland Kirk, 1902–1970. Courtesy Blackstone-Shelburne, N.Y.

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10 CHAPTER 1

Organization of a Crime Laboratory 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. At present, nearly four hundred public crime laboratories operate at various levels of government (federal, state, county, and municipal)—more than three times the number of crime laboratories operating in 1966.

The size and diversity of crime laboratories make it impossible to select any one model that best describes a typical crime laboratory. 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 office; some work with the laboratories of the medical examiner or coroner. Far fewer are affili- ated with universities or exist as independent agencies in government. Laboratory staff sizes range from one person to more than a hundred, and their services may be diverse or specialized, depending on the responsibilities of the agency that houses the laboratory.

The Growth of Crime Laboratories Crime laboratories have mostly been organized by agencies that either foresaw their potential application to criminal investigation or were pressed by the increasing demands of casework. Several reasons explain the unparalleled growth of crime laboratories during the past thirty-five years. Supreme Court decisions in the 1960s were responsible for greater police emphasis on securing scientifically evaluated evidence. The requirement to advise criminal suspects of their constitutional rights and their right of immediate access to counsel has all but eliminated confes- sions 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. This factor alone would probably have accounted for the increased use of crime laboratory services by police agencies, but only a small percentage of police investigations generate evidence requiring scientific examination. There is, however, one im- portant exception to this observation: drug-related arrests. All illicit-drug seizures must be sent to a forensic laboratory for confirmatory 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 inundated with drug specimens. Current estimates indicate that nearly half of all requests for examination of forensic evidence deal with abused drugs.

Future Challenges A more recent impetus leading to the growth and maturation of crime laboratories has been the advent of DNA profiling. Since the early 1990s, this technology has progressed to the point at which traces of blood, semen stains, hair, and saliva residues left behind on stamps and cups, as well as bite marks, have made possible the individualization or near-individualization of biolog- ical evidence. 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 the technology have affected the structure of the forensic laboratory as has no other technology in the past fifty years. Likewise, DNA profiling has become the dominant factor in explaining how the general public perceives the workings and capabilities of the modern 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 evidence for DNA and to acquire DNA profiles, as mandated by state laws, from the hundreds of thousands of individuals con- victed of crimes. This endeavor has already added many new scientists to the field 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 substantial backlog of unana- lyzed DNA samples from crime scenes. The number of unanalyzed casework DNA samples reported by state and national agencies is more than 57,000. The estimated number of untested convicted offender samples is over 500,000. In an attempt to eliminate the backlog of convicted

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offender or arrestee samples to be analyzed 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 or outsourcing samples to private laboratories for analysis.

Beginning in 2008, California began collecting DNA samples from all people arrested on suspicion of a felony, not waiting until a person is convicted. The state’s database, with approxi- mately one million DNA profiles, is already the third largest in the world, behind those maintained by the United Kingdom and the FBI. The federal government plans to begin doing the same.

Types of Crime Laboratories Historically, a federal system of government, combined with a desire to retain local control, has produced 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.

FEDERAL CRIME LABORATORIES The federal government has no single law enforcement or investigative agency with unlimited jurisdiction. Four major federal crime laboratories have been created to help investigate 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 (see Figure 1–4). Its expertise and technology support its broad investigative powers. The Drug Enforcement Administration laboratories (Department of Justice) analyze drugs seized in viola- tion of federal laws regulating the production, sale, and transportation of drugs. The laboratories of the Bureau of Alcohol, Tobacco, Firearms and Explosives (Department of Justice) analyze alcoholic beverages and documents relating to alcohol and firearm excise tax law 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 Service maintains laboratories concerned with criminal investigations relating to the postal service. Each of these federal facilities will offer its expertise to any local agency that requests assistance in relevant investigative matters.

STATE AND LOCAL CRIME LABORATORIES Most state governments maintain a crime laboratory to service state and local law enforcement agencies that do not have ready access to a laboratory. Some states, such as Alabama, California, Illinois, Michigan, New Jersey, Texas, Washington, Oregon, Virginia, and Florida, have developed a comprehensive 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. The concept of a regional laboratory operating as part of a statewide 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 expertise and equipment.

INTRODUCTION 11

FIGURE 1–4 (a) Exterior and (b) interior views of the FBI crime laboratory in Quantico, Virginia. Courtesy AP Wide World Photos

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12 CHAPTER 1

Local laboratories provide services to county and municipal agencies. Generally, these facil- ities operate independently of the state crime laboratory and are financed directly by local gov- ernment. 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 maintain their own crime laboratories, usually under the direction of the local police de- partment. Frequently, high population and high crime rates combine to make a municipal facility, such as that of New York City, the largest crime laboratory in the state.

Services of the Crime Laboratory Bearing in mind the independent development of crime laboratories in the United States, the wide variation in total services offered in different communities is not surprising. There are many rea- sons 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 staffing limitations.

In recent years, many local crime laboratories have been created solely to process drug specimens. Often these facilities were staffed with few personnel and operated under limited budgets. Although many have expanded their forensic services, some still primarily perform drug analyses. However, even among crime laboratories providing services beyond drug identification, the diversity and quality of services rendered varies significantly. For the purposes of this text, I have taken the liberty of arbitrarily designating the following units as those that should constitute 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 chem- istry, physics, and geology to the identification and comparison of crime-scene evidence. It is

staffed by criminalists who have the expertise to use chemical tests and modern analytical instrumentation to examine items as diverse as drugs, glass, paint, explosives, and soil. In a laboratory that has a staff large enough to permit spe- cialization, the responsibilities of this unit may be further subdivided into drug identification, soil and mineral analysis, and examination of a variety of trace physical evidence.

BIOLOGY UNIT The biology unit is staffed with biologists and biochemists who identify and perform DNA profiling on dried bloodstains and other body fluids, compare hairs and fibers, and identify and compare botanical materials such as wood and plants (see Figure 1–5).

FIREARMS UNIT The firearms unit examines firearms, discharged bullets, car- tridge cases, shotgun shells, and ammunition of all types. Garments and other objects are also examined to detect firearms discharge residues and to approxi- mate the distance from a target at which a weapon was fired. The basic princi- ples of firearms examination are also applied here to the comparison of marks made by tools (see Figure 1–6).

DOCUMENT EXAMINATION UNIT The document examination unit studies the handwriting and typewriting on questioned documents to ascertain authenticity and/or source. Related responsibilities include analyzing paper and ink and examining indented writings (the term usually applied to the partially visible depressions appearing on a sheet of paper underneath the one on which the visi- ble writing appears), obliterations, erasures, and burned or charred documents (see Figure 1–7).

PHOTOGRAPHY UNIT A complete photographic laboratory examines and records physical evidence. Its procedures may require the use of highly special- ized photographic techniques, such as digital imaging, infrared, ultraviolet, and X-ray photography, to make invisible information visible to the naked eye. This unit also prepares photographic exhibits for courtroom presentation.

FIGURE 1–5 A forensic scientist performing DNA analysis. Courtesy Mauro Fermariello, Photo Researchers, Inc.

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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 laboratory 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 the al- coholic consumption of individuals. Often the toxicology section also trains operators and main- tains and services these instruments.

LATENT FINGERPRINT UNIT The latent fingerprint unit processes and examines evidence for latent fingerprints when they are submitted in conjunction with other laboratory examinations.

POLYGRAPH UNIT The polygraph, or lie detector, has come to be recognized as an essential tool of the criminal investigator rather than the forensic scientist. However, during the formative years of polygraph technology, many police agencies incorporated this unit into the laboratory’s ad- ministrative structure, where it sometimes remains today. In any case, its functions are handled by people trained in the techniques of criminal investigation and interrogation.

VOICEPRINT ANALYSIS UNIT In cases involving telephoned threats or tape-recorded mes- sages, investigators may require the skills of the voiceprint analysis unit to tie the voice to a par- ticular suspect. To this end, a good deal of casework has been performed with the sound spectrograph, an instrument that transforms speech into a visual 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 individual and that the voiceprint displays this uniqueness.

CRIME-SCENE INVESTIGATION UNIT The concept of incorporating crime-scene evidence collection into the total forensic science service is slowly gaining recognition 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 later 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.

FIGURE 1–6 A forensic analyst examining a firearm. Courtesy Mediacolors, Alamy Images

WEBEXTRA 1.1 Take a Tour of a Forensic Laboratory www.mycrimekit.com

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Fingerprints may be detectable on paper using a variety of chemical developing techniques (pp. 403–404).

Cellophane tape was used to seal our envelopes containing the anthrax letters. The fitting together of the serrated ends of the tape strips confirmed that they were orn in succession from the same roll of tape (pp. 62–63)

DNA may be recovered from saliva residues on the back of a stamp (pp. 284–286). However, in this case, the stamp is printed onto the envelope.

Ink analysis may reveal a pen’s manufacturer (pp. 463–464).

Paper examination may identify a manufacturer. General appearance, watermarks, fiber analysis, and chemical analysis of pigments, additives, and fillers may reveal a paper's origin (p. 468).

Photocopier toner may reveal its manufacturer through chemical and physical properties (pp. 457–458).ndented writing may be deposited

on paper left underneath a sheet of paper being written upon. Electrostatic maging is used to visualize indented mpressions on paper (p. 462).

Handwriting examination reveals that block lettering is consistent with a single writer who wrote three other anthrax letters (pp. 452–457).

DNA may be recovered from saliva used to seal an envelope (pp. 284–286)

Trace evidence, such as hairs and fibers, may be present within the contents of the envelope.

FIGURE 1–7 An envelope containing anthrax spores along with an anonymous letter was sent to the office of Senator Tom Daschle shortly after the terrorist attacks of September 11, 2001. A variety of forensic skills were used to examine the envelope and letter. Also, bar codes placed on the front and back of the envelope by mail-sorting machines contain address information and information about where the envelope was first processed. Courtesy Getty Images Inc. - Getty News

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Laboratory administrators need to keep open the lines of communication among analysts (civilian and uniform), crime-scene investigators, and police personnel. Inevitably, forensic investigations require the skills of many individuals. One notoriously high-profile investigation illustrates this process—the search to uncover the source of the anthrax letters mailed shortly after September 11, 2001. Figure 1–7 shows one of the letters and illustrates the multitude of skills required in the investigation—skills possessed by forensic chemists and biologists, fingerprint examiners, and forensic document examiners.

Functions of the Forensic Scientist Although a forensic scientist relies primarily on scientific knowledge and skill in performing analy- ses in the laboratory, a good deal of the forensic scientists’s time is spent in the courtroom, where the ultimate significance of the evidence is determined. The forensic scientist must not only analyze physical evidence but also persuade a jury to accept the conclusions derived from that analysis.

Analysis of Physical Evidence First and foremost, the forensic scientist must be skilled in applying the principles and techniques of the physical and natural sciences to analyze the many types of physical evidence that may be recovered during a criminal investigation. Of the three major avenues available to police investi- gators for assistance in solving a crime—confessions, eyewitness accounts by victims or wit- nesses, and the evaluation of physical evidence retrieved from the crime scene—only physical evidence is free of inherent error or bias.

THE IMPORTANCE OF PHYSICAL EVIDENCE Criminal cases are replete with examples of indi- viduals who were incorrectly 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 surrounding the commission of a crime. These errors may be compounded by misleading eyewitness statements and inappropriate con- fessions. These same concerns don’t apply to physical evidence.

What about physical evidence allows investigators to sort out facts as they are and not what one wishes they were? The hallmark of physical evidence is that it must undergo scientific in- quiry. Science derives its integrity from adherence to strict guidelines that ensure the careful and systematic collection, organization, and analysis of information—a process known as the scientific method. The underlying principles of the scientific method provide a safety net to ensure that the outcome of an investigation is not tainted by human emotion or compromised by distorting, belittling, or ignoring contrary evidence.

The scientific method begins by formulating a question worthy of investigation, 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 scientific 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 findings even when they wish they were different. Finally, when the hypothesis is validated by experimentation, it becomes suitable as scientific 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 scientific 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 scientific examinations. In Frye v. United States,2 the court stated the following:

Just when a scientific principle or discovery crosses the line between the experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone the evidential force of the principle must be recognized, and while the courts will go a long way in admit- ting expert testimony deduced from a well-recognized scientific principle or discovery, the

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

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

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thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.

To meet the Frye standard, the court must decide whether the questioned procedure, tech- nique, or principle is “generally accepted” by a meaningful segment of the relevant scientific community. In practice, this approach required the proponent of a scientific test to present to the court a collection of experts who could testify that the scientific issue before the court is gener- ally accepted by the relevant members of the scientific community. Furthermore, in determining whether a novel technique meets criteria associated with “general acceptance,” courts have fre- quently 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 this approach has engendered a great deal of debate as to whether it is sufficiently flexible to deal with new and novel scientific issues that may not have gained widespread support within the scientific community.

OTHER STANDARDS OF ADMISSIBILITY As an alternative to the Frye standard, some courts came to believe that the Federal Rules of Evidence espoused a more flexible standard that did not rely on general acceptance as an absolute prerequisite for admitting scientific evidence. Part of the Federal Rules of Evidence governs the admissibility of all evidence, including expert testimony, in federal courts, and many states have adopted codes similar to those of the Federal Rules. Specifically, Rule 702 of the Federal Rules of Evidence deals with the admissibility of expert testimony:

If scientific, technical, or other specialized knowledge will assist the trier of fact to under- stand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the tes- timony 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 Pharmaceuticals, Inc.,3 the U.S. Supreme Court asserted that “general acceptance,” or the Frye standard, is not an absolute prerequisite to the admissibility of scientific 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 foundation 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 scientific evidence.

JUDGING SCIENTIFIC EVIDENCE What the Court advocates in Daubert is that trial judges as- sume the ultimate responsibility for acting as a “gatekeeper” in judging the admissibility and re- liability of scientific evidence presented in their courts (see Figure 1–8). The Court offered some guidelines as to how a judge can gauge the veracity of scientific evidence, emphasizing that the inquiry should be flexible. Suggested areas of inquiry include the following:

1. Whether the scientific technique or theory can be (and has been) tested 2. Whether the technique or theory has been subject to peer review and publication 3. The technique’s potential rate of error 4. Existence and maintenance of standards controlling the technique’s operation 5. Whether the scientific theory or method has attracted widespread acceptance within a rele-

vant scientific community

Some legal practitioners have expressed concern that abandoning Frye’s general-acceptance test will result in the introduction of absurd and irrational pseudoscientific claims in the court- room. The Supreme Court rejected these concerns:

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

3 509 U.S. 579 (1993).

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

We conclude that Daubert’s general holding—setting forth the trial judge’s general “gate- keeping” obligation—applies not only to testimony based on “scientific” 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 specific 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 “flexible,” and Daubert’s list of spe- cific factors neither necessarily nor exclusively applies to all experts in every case.

A leading case that exemplifies the type of flexibility and wide discretion that the Daubert ruling apparently gives trial judges in matters of scientific inquiry is Coppolino v. State.5 Here a medical examiner testified to his finding that the victim had died of an overdose of a drug known as succinylcholine chloride. This drug had never before been detected in the human body. The medical examiner’s findings were dependent on a toxicological report that identified an abnor- mally high concentration of succinic acid, a breakdown product of the drug, in the victim’s body. The defense argued that this test for the presence of succinylcholine chloride was new and the absence of corroborative experimental data by other scientists meant that it had not yet gained general acceptance in the toxicology profession. The court, in rejecting this argument, recognized the necessity for devising new scientific tests to solve the special problems that are continually arising in the forensic laboratory. It emphasized, however, that although these tests may be new and unique, they are admissible only if they are based on scientifically valid principles and tech- niques: “The tests by which the medical examiner sought to determine whether death was caused by succinylcholine chloride were novel and devised specifically for this case. This does not ren- der the evidence inadmissible. Society need not tolerate homicide until there develops a body of medical literature about some particular lethal agent.”

FIGURE 1–8 Sketch of a U.S. Supreme Court hearing. © Art Lien, Court Artist

4 526 U.S. 137 (1999). 5 223 So. 2d 68 (Fla. Dist. Ct. App. 1968), app. dismissed, 234 So. 2d 120 (Fla. 1969), cert. denied, 399 U.S. 927 (1970).

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

Dr. Coppolino’s Deadly House Calls A frantic late-night telephone call to Dr. Juliette Karow brought her to the Longport Key, Florida, home of Drs. Carl and Carmela Coppolino. Carl had called for Dr. Karow’s help be- cause he believed Carmela was dying. He said she had com- plained of chest pains earlier in the evening and he was certain she had suffered a heart attack. Dr. Karow arrived to find Carmela beyond help.

Although Dr. Karow felt that the scene in the room appeared staged, and her own observations of Carmela’s body did not support Carl’s claim of heart trouble, she agreed to sign 32-year-old Carmela’s death certificate. Dr. Karow cited “coro- nary occlusion” as the cause of death but reported the death to the local police department. The investigating officer was sat- isfied that Dr. Karow had correctly listed the cause of death, so he did not apply the law that required that an autopsy be performed. The medical examiner could not order an autopsy without a request from the police or the district attorney, which was not forthcoming. Thus, Carmela Coppolino’s body, unex- amined by anyone, was buried in her family’s plot in her home state of New Jersey.

A little more than a month later, Carl married a moneyed socialite, Mary Gibson. News of Carl’s marriage infuriated Mar- jorie Farber, a former New Jersey neighbor of Dr. Coppolino who had been having an affair with the good doctor. Soon Marjorie had an interesting story to recount to investigators. Her husband’s death two years before, although ruled to be from nat- ural causes, had actually been murder! Carl, an anesthesiologist, had given Marjorie a syringe containing 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 finished the job by suffocating William with a pillow.

In a cruel and ironic twist, Carl called his wife, Carmela, to sign William Farber’s death certificate. She listed the cause of death, at Carl’s insistence, as coronary artery disease. This type of death is common, especially in men in their fifties. Such deaths are rarely questioned, and the Department of Health accepted the certificate without any inquiry.

Marjorie Farber’s astonishing story was supported in part by Carl’s recent increase in his wife’s life insurance. Carmela’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 information, authorities in New Jersey and Florida now obtained exhumation orders for both William Farber and Carmela Coppolino. After examination of both bodies, Dr. Coppolino was charged with the murders of William and Carmela.

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Provision of Expert Testimony Because their work product may ultimately be a factor in determining a person’s guilt or innocence, forensic scientists may be required to testify with respect to 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 satisfaction of a trial judge that he

Officials decided to try Dr. Coppolino first in New Jersey for the murder of William Farber. Coppolino was represented by the famous defense attorney F. Lee Bailey. The Farber autopsy did not reveal any evidence of poisoning, but seemed to show strong evidence of strangulation. The absence of toxicological findings left the jury to deliberate the conflicting medical expert testimony versus the sensational story told by a scorned and embittered woman. In the end, Bailey secured an acquittal for his client.

The Florida trial presented another chance to bring Carl Coppolino to justice. Florida officials called on the experienced New York City medical examiner Dr. Milton Halpern and his colleague, toxicologist Dr. Charles Umberger, to determine how Carl Coppolino had killed his wife. Recalling Dr. Coppolino’s career as an anesthesiologist, Halpern theorized that Coppolino had exploited his access to the many potent drugs used during surgery to commit these murders, specifically an injectable paralytic agent called succinylcholine chloride.

After having Carmela’s body exhumed, Halpern examined her body with a magnifying glass in search of an injection site. He found that Carmela had been injected in her left buttock shortly before her death. Dr. Umberger’s mission as the toxicol- ogist in this case was to prove the administration of succinyl- choline chloride by chemical analysis of Carmela’s tissues.

This presented a serious problem because succinylcholine was purported to be untraceable in human tissue. The drug breaks down in the body to succinic acid and choline, both of which are naturally occurring chemicals in the human body. The chemical method necessary to make this determination did not exist at the time of the murder.

Ultimately, Dr. Umberger developed a completely novel procedure for detecting succinylcholine chloride. He isolated elevated levels of succinic acid in Carmela’s brain, which proved that she had received a large dose of the paralytic drug shortly before her death. This evidence, along with the finding 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.

On appeal, the defense raised an interesting point of law. Can a defendant be convicted of murder based on a series of tests that were specifically devised for this case? Tests that indirectly showed that Carmela had been injected with suc- cinylcholine chloride had never before been used in a criminal trial. The court ruled that the novelty of a scientific method does not preclude its significance to a criminal prosecution. Just be- cause an otherwise valid method was developed specifically for this trial and had not yet been proven in court did not mean that the murderer should be allowed to get away with the perfect crime. The conviction of Dr. Coppolino was upheld.

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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 matter 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 through experience, training, education, or a combination sufficient grounds for quali- fication as an expert witness.

DETERMINING COMPETENCE In court, the qualifying questions that counsel asks the expert are often directed toward demonstrating the witness’s ability and competence pertaining to the matter at hand. Competency may be established by having him or her cite educational degrees, participation in special courses, membership in professional societies, and any professional arti- cles or books published. Also important is the number of years of occupational experience the witness has 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 train- ing under an experienced examiner with independent study. Of course, formal education provides the scientist with a firm foundation 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 qualifications, the opposing attorney is given the opportunity to cross-examine the witness and to point out weaknesses in his or her background and knowledge. Most courts are reluctant to disqualify an individual as an expert even when presented with someone whose background is only remotely associated with the issue at hand. The question of what credentials are suitable for qualification as an expert is ambiguous and highly subjective and one that the courts wisely try to avoid. However, the weight that a judge or jury assigns to “expert” testimony in subsequent deliberations is quite another matter. Undoubt- edly, education and experience have considerable bearing on the value assigned to the expert’s opinions. Just as important may be the witness’s demeanor and ability to explain scientific 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, who must endeavor to prepare themselves adequately for this undertaking.

EXPERT TESTIMONY The ordinary or lay witness must give testimony on events or observations that arise from personal knowledge. This testimony must be factual and, with few exceptions, can- not 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 opin- ion as to the significance of the findings. The views expressed are accepted only as representing the expert’s opinion and may later be accepted or ignored in jury deliberations (see Figure 1–9).

It must be recognized that the expert cannot render any view with absolute certainty. At best, he or she may only be able to offer an opinion that is based on a reasonable scientific certainty 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 must not be reluctant to discuss impartially any findings that could minimize the significance of the analysis. The forensic scien- tist should not be an advocate of one party’s cause, but only an advocate of truth. An adversary system of justice must give the prosecutor and defense ample opportunity to offer expert opinions and to argue the merits of such testimony. Ultimately, the duty of the judge or jury is to weigh the pros and cons of all the information presented in deciding guilt or innocence.

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 lit- tle or no value if relevant evidence cannot be properly recognized, collected, and preserved at the site of a crime. For this reason, the forensic staff must have responsibilities that will influence 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 crim- inal investigators retrieve evidence. These technicians are trained by the laboratory staff to recog- nize and gather pertinent physical evidence at the crime scene. They are administratively assigned

WEBEXTRA 1.2 Watch a Forensic Expert Witness Testify—I www.mycrimekit.com

WEB EXTRA 1.3 Watch a Forensic Expert Witness Testify—II www.mycrimekit.com

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to the laboratory to facilitate their continued exposure to forensic techniques and procedures. They have at their disposal all the proper tools and supplies for proper collection and packaging of evi- dence for future scientific examination.

Unfortunately, many police forces have still not adopted this approach. Often a patrol officer or detective is charged with collecting the evidence. His or her effectiveness in this role depends on the extent of his or her training and working relationship with the laboratory. For maximum use of the skills of the crime laboratory, training of the crime-scene investigator must go beyond superficial 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 officers in evidence collection and their familiarization with the capabilities of a crime laboratory should not be restricted to a select group of personnel on the force. Every officer engaged in fieldwork, whether it be traffic, patrol, investigation, or juvenile control, often must process evidence for laboratory examination. Obviously, it would be a diffi- cult and time-consuming operation to give everyone the in-depth training and attention that a qualified criminal investigator requires. However, familiarity with crime laboratory services and capabilities can be facilitated through periodic lectures, laboratory tours, and dissemination of manuals prepared by the laboratory staff that outline proper methods for collecting and submit- ting physical evidence to the laboratory. Examples of such manuals are shown in Figure 1–10.

A brief outline describing the proper collection and packaging of common types of physical evidence is found in Appendix I. The procedures and information summarized in this appendix are discussed in greater detail in forthcoming chapters.

Other Forensic Science Services Even though this textbook is devoted to describing the services normally provided by a crime lab- oratory, the field of forensic science is by no means limited to the areas covered in this book. A number of specialized forensic science services outside the crime laboratory are routinely avail- able to law enforcement personnel. These services are important aids to a criminal investigation and require the involvement of individuals who have highly specialized skills.

FIGURE 1–9 An expert witness testifying in court. Courtesy Jeff Siner, Corbis/Sygma

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WEBEXTRA 1.4 Explore Forensic Dentistry www.mycrimekit.com

INTRODUCTION 21

Forensic Psychiatry Forensic psychiatry is a specialized area in which the relationship between human behavior and legal proceedings is examined. Forensic psychiatrists are retained for both civil and criminal lit- igations. For civil cases, forensic psychiatrists normally determine whether people are competent to make decisions about preparing wills, settling property, or refusing medical treatment. For criminal cases, they evaluate behavioral disorders and determine whether people are competent to stand trial. Forensic psychiatrists also examine behavioral patterns of criminals as an aid in developing a suspect’s behavioral profile.

Forensic Odontology Practitioners of forensic odontology help identify victims when the body is left in an unrecog- nizable state. Teeth are composed of enamel, the hardest substance in the body. Because of enamel’s resilience, the teeth outlast tissues and organs as decomposition begins. The character- istics of teeth, their alignment, and the overall structure of the mouth provide individual evidence for identifying a specific person. With the use of dental records such as X-rays and dental casts or even a photograph of the person’s smile, a set of dental remains can be compared to a suspected victim. Another application of forensic odontology to criminal investigations is bite mark analy- sis. At times in assault cases, bite marks are left on the victim. A forensic odontologist can com- pare the marks left on a victim and the tooth structure of the suspect. See Figure 1–11.

Forensic Engineering Forensic engineers are concerned with failure analysis, accident reconstruction, and causes and origins of fires or explosions. Forensic engineers answer questions such as these: How did an ac- cident or structural failure occur? Were the parties involved responsible? If so, how were they re- sponsible? Accident scenes are examined, photographs are reviewed, and any mechanical objects involved are inspected.

Forensic Computer and Digital Analysis Forensic computer science is a new and fast-growing field that involves the identification, collection, preservation, and examination of information derived from computers and other digital devices, such as cell phones. Law enforcement aspects of this work normally involve the recovery of deleted or

FIGURE 1–10 Representative evidence-collection guides prepared by various police agencies.

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overwritten data from a computer’s hard drive and the tracking of hacking activities within a com- promised system. The field of forensic computer analysis will be addressed in detail in Chapter 19.

Forensic Science on the Internet There are no limits to the amount or type of information that can be found on the Internet. The fields 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 Web pages range from simple explanations of the various fields of forensics to intricate details of crime-scene reconstruction. People can also find information on which colleges offer degree programs in forensics or pages posted by law enforcement agencies that detail their activities, as well as possible employment opportunities.

General Forensics Sites Reddy’s Forensic Home Page (www.forensicpage.com) is a valuable starting point. This site is a collection of forensic Web pages listed under categories such as new links in forensics; general forensic information sources; associations, colleges, and societies; literature and journals; forensic laboratories; general Web pages; forensic-related mailing lists and newsgroups; universities; con- ferences; and various forensic fields of expertise.

Another Web site offering a multitude of information related to forensic science is Zeno’s Forensic Site (forensic.to/forensic.html). Here users can find links to forensic education and expert consultation, as well as a wealth of information concerning specific fields of forensic science.

A comprehensive and useful Web site for those interested in law enforcement is Officer.com (www.officer.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 organization sites, criminal justice organizations, law research pages, and police mailing-list directories.

Web Sites on Specific Topics AN INTRODUCTION TO FORENSIC FIREARM IDENTIFICATION This Web site contains an extensive collection of information relating to the identification of firearms. An individual can

FIGURE 1–11 (a) Bite mark on victim’s body. (b) Comparison to suspect’s teeth. Courtesy David Sweet, DMD, Ph.D., DABFP BOLD Forensic Laboratory, Vancouver, BC Canada

(a) (b)

WEBEXTRA 1.5 An Introduction to Forensic Firearms Identification www.mycrimekit.com

WEBEXTRA 1.6 Carpenter’s Forensic Science Resources www.mycrimekit.com

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explore in detail how to examine bullets, cartridge cases, and clothing for gunshot residues and suspect shooters’ hands for primer residues. Information on the latest technology involving the automated firearms search system IBIS can also be found on this site.

CARPENTER’S FORENSIC SCIENCE RESOURCES This site provides a bibliography with hyper- text references pertaining to various aspects of criminal investigations involving forensic evi- dence. For example, the user can find references about DNA, fingerprints, hairs, fibers, and questioned documents as they relate to crime scenes and assist investigations. This Web site 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 packaging and analysis of bloodstains, seminal fluids, hairs, fibers, paint, glass, firearms, documents, and fingerprints can be found through this Web site. It explains the impor- tance of inspecting the crime scene and the impact forensic evidence has on the investigation.

CRIME AND CLUES Users interested in learning about the forensic aspects of fingerprinting will find this a useful and informative Web site. The site covers the history of fingerprints as well as subjects pertaining to the development of latent fingerprints. The user will also find links to other Web sites covering a variety of subjects pertaining to crime-scene investigation, documentation 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 data- base on the subject. They can also explore actual evidence gathered from notorious crime scenes. Users will be able to employ deductive skills and forensic knowledge while playing an interactive 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 disci- plines. Topics such as fingerprints, fire and arson, and DNA analysis are described in informative layperson’s terms. Case histories describe the application of forensic evidence to criminal inves- tigations. Emphasis is placed on securing and documenting the crime scene. The site directs the reader to other important forensic links.

QUESTIONED-DOCUMENT EXAMINATION This basic, informative Web page answers fre- quently asked questions concerning document examination, explains 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.

WEBEXTRA 1.9 Interactive Investigator—Détective Interactif www.mycrimekit.com

WEBEXTRA 1.11 Questioned-Document Examination www.mycrimekit.com

WEBEXTRA 1.10 The Chemical Detective www.mycrimekit.com

WEBEXTRA 1.8 Crime and Clues www.mycrimekit.com

WEBEXTRA 1.7 Crime-Scene Investigation www.mycrimekit.com

In its broadest definition, forensic science is the application of science to criminal and civil laws. This book emphasizes the application of science to the criminal and civil laws that are enforced by police agencies in a criminal justice system. 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 or compare physical evidence.

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. At present, approximately four hundred public crime laboratories

operate at various levels of government—federal, state, county, and municipal.

The technical support provided by crime laboratories can be assigned to five basic services. The physical science unit uses the principles of chemistry, physics, and geology to iden- tify and compare physical evidence. The biology unit uses knowledge of biological sciences to investigate blood sam- ples, body fluids, hair, and fiber samples. The firearms unit investigates discharged bullets, cartridge cases, shotgun shells, and ammunition. The document examination unit per- forms handwriting analysis and other questioned-document examination. Finally, the photography unit uses specialized

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review questions

1. The application of science to law describes ___________.

2. The fictional exploits of ___________ excited the imag- ination of an emerging generation of forensic scientists and criminal investigators.

3. A system of personal identification using a series of body measurements was first devised by ___________.

4. ___________ is responsible for developing the first statistical study proving the uniqueness of fingerprints.

5. The Italian scientist ___________ devised the first workable procedure for typing dried bloodstains.

6. The comparison microscope became an indispensable tool of firearms examination through the efforts of ___________.

7. Early efforts at applying scientific principles to docu- ment examination are associated with ___________.

8. The application of science to criminal investigation was advocated by the Austrian magistrate ___________.

9. One of the first functional crime laboratories was formed in Lyons, France, under the direction of ___________.

10. The transfer of evidence that occurs when two objects come in contact with one another was a concept first advocated by the forensic scientist ___________.

11. The first forensic laboratory in the United States was cre- ated in 1923 by the ___________ Police Department.

12. The state of ___________ is an excellent example of a geographical area in the United States that has created a system of integrated regional and satellite laboratories.

13. In contrast to the United States, Britain’s crime labora- tory system is characterized by a national system of ___________ laboratories.

14. The increasing demand for ___________ analyses has been the single most important factor in the recent ex- pansion of crime laboratory services in the United States.

15. Four important federal agencies offering forensic services are ___________, ___________, ___________, and ___________.

16. A decentralized system of crime laboratories currently exists in the United States under the auspices of various governmental agencies at the ___________, ___________, ___________, and ___________ levels of government.

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

18. The examination of blood, hairs, fibers, and botanical materials 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 examination of body fluids and organs for drugs and poisons is a function of the ___________ unit.

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

22. The “general acceptance” principle, which serves as a criterion for the judicial admissibility of scientific evi- dence, was set forth in the case of ___________.

23. In the case of ___________, the Supreme Court ruled that, in assessing the admissibility of new and unique scientific tests, the trial judge did not have to rely solely on the concept of “general acceptance.”

photographic techniques to record and examine physical evi- dence. Some crime laboratories offer the optional services of toxicology, fingerprint analysis, polygraph administration, voiceprint analysis, and crime-scene investigation and evi- dence collection.

A forensic scientist must be skilled in applying the prin- ciples and techniques of the physical and natural sciences to the analysis of the many types of evidence that may be recov- ered during a criminal investigation. A forensic scientist may also provide expert court testimony. An expert witness is called on to evaluate evidence based on specialized training and experience and to express an opinion as to the significance of the findings. Also, forensic scientists participate in training law enforcement personnel in proper recognition, collection, and preservation of physical evidence.

The Frye v. United States decision set guidelines for deter- mining the admissibility of scientific evidence into the court- room. To meet the Frye standard, the evidence in question must be “generally accepted” by the scientific community. However, in the 1993 case of Daubert v. Merrell Dow Pharmaceuticals, Inc., the U.S. Supreme Court asserted that the Frye standard is not an absolute prerequisite to the admissibility of scientific evidence. Trial judges were said to be ultimately responsible as “gatekeepers” for the admissibility and validity of scientific evidence presented in their courts.

A number of special forensic science services are avail- able to the law enforcement community to augment the services of the crime laboratory. These services include forensic psychi- atry, forensic odontology, forensic engineering, and forensic computer and digital analysis.

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24. True or False: The U.S. Supreme Court decision in Kumho Tire Co., Ltd. v. Carmichael restricted the “gate- keeping” role of a trial judge only to scientific testimony. ___________

25. A Florida case that exemplifies the flexibility and wide discretion that the trial judge has in matters of scientific inquiry is ___________.

26. A(n) ___________ is a person who can demonstrate a par- ticular skill or has knowledge in a trade or profession that will help the court determine the truth of the matter at issue.

27. 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. ___________

28. True or False: The testimony of an expert witness incor- porates his or her personal opinion relating to a matter he or she has either studied or examined. ___________

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

application and critical thinking

1. Most crime labs in the United States are funded and op- erated by the government and provide services free to police and prosecutors. Great Britain, however, uses a quasi-governmental agency that charges fees for its services and keeps any profits it makes. Suggest poten- tial strengths and weaknesses of each system.

2. Police investigating an apparent suicide collect the fol- lowing 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 relevant to the decision to reject the appeal? Explain your answer.

further references

Berg, Stanton O., “Sherlock Holmes: Father of Scientific Crime Detection,” Journal of Criminal Law, Criminology and Police Science 61, no. 3 (1970): 446–52.

Cohen, Stanley A., “The Role of the Forensic Expert in a Criminal Trial,” Canadian Society of Forensic Science Journal 12 (1979): 75.

Doyle, Sir Arthur Conan, The Complete Sherlock Holmes, vol. 1. New York: Doubleday, 1956.

Gallop, A. M. C., “Forensic Science Coming of Age,” Science & Justice, 43 (2003): 55.

James, S. H., and Nordby, J. J., eds., Forensic Science—An Introduction to Scientific and Investigative Techniques, 3rd ed. Boca Raton, Fla.: CRC Press, 2009.

Kagan, J. D., “On Being a Good Expert Witness in a Crimi- nal Case,” Journal of Forensic Sciences 23 (1978): 190.

Lucas, D. M., “North of 49—The Development of Forensic Science in Canada,” Science & Justice, 37 (1997): 47.

Midkiff, C. R., “More Mountebanks,” in R. Saferstein, ed., Forensic Science Handbook, vol. 2, 2nd ed. Upper Saddle River, N.J.: Prentice Hall, 2005.

National Research Council, Strengthening Forensic Science in the United States: A Path Forward, Washington, D.C.: The National Academies Press, 2009, http://books.nap .edu/openbook.php?record_id=12589&page�R1

Sapir, Gil I., “Legal Aspects of Forensic Science,” in R. Saferstein, ed., Forensic Science Handbook, vol. 1, 2nd ed. Upper Saddle River, N.J.: Prentice Hall, 2002.

Starrs, James E., “Mountebanks among Forensic Scientists,” in R. Saferstein, ed., Forensic Science Handbook, vol. 2, 2nd ed. Upper Saddle River, N.J.: Prentice Hall, 2005.

Waggoner, Kim. “The FBI Laboratory: 75 Years of Forensic Science Service,” Forensic Science Communications, 9, no. 4 (2007). www.fbi.gov/hq/lab/fsc/backissu/oct2007/ research/2007_10_research01_test1.htm

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JonBenet Ramsey: Who Did It?

Patsy Ramsey awoke just after five A.M. on December 26, 1996, and walked downstairs to her kitchen. At the foot of the staircase, she found a two-and-a-half-page note saying that her 6-year-old daughter, JonBenet, had been kidnapped. The note contained a ransom demand of $118,000. Patsy and John Ramsey were in the upper crust of Boulder, Colorado, society. In the span of five short years, John had built his computer company into a billion- dollar corporation. When the police arrived to investigate, it

was quite apparent to all 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 find JonBenet. The house was not sealed off; in fact, four friends along with the Ramsey 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 floor.

The murder of JonBenet Ramsey remains as baffling a mystery today as it was on its first day. Ample physical evidence exists to support the theory that the crime was committed by an outsider, and also that JonBenet was murdered by someone who resided in the Ramsey household. Twelve years after the commission of the crime, Boulder district attorney Mary T. Lacy issued a statement exonerating members of the Ramsey family on the basis of DNA evidence. Perhaps better care in securing and processing the crime scene could have resolved some of the crime’s outstanding questions. A more detailed analysis of this crime can be found on pages 282–285.

headline news

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After studying this chapter you should be able to: • Define physical evidence

• Discuss the responsibilities of the first police officer who arrives at a crime scene

• Explain the steps to be taken to thoroughly record the crime scene

• Describe proper procedures for conducting a systematic search of a crime scene for physical evidence

• Describe proper techniques for packaging common types of physical evidence

• Define and understand the concept of chain of custody

• Relate what steps are typically required to maintain appropriate health and safety standards at the crime scene

• Understand the implications of the Mincey and Tyler cases

the crime scene

buccal swab chain of custody finished sketch physical evidence rough sketch standard/reference

sample substrate control

KEY TERMS

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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 its perpetrator

28 CHAPTER 2

Processing the Crime Scene As automobiles run on gasoline, crime laboratories “run” on physical evidence. Physical evi- dence encompasses any and all objects that can establish that a crime has or has not been com- mitted or can link a crime and its victim or its perpetrator. But if physical evidence is to be used effectively to aid the investigator, its presence first must be recognized at the crime scene. If all the natural and commercial objects within a reasonable distance of a crime were gathered so that the scientist could uncover significant clues from them, the deluge of material would quickly immobilize the laboratory facility. Physical evidence can achieve its optimum value in criminal investigations only when its collection is performed with a selectivity governed by the collector’s thorough knowledge of the crime laboratory’s techniques, capabilities, and limitations.

Forthcoming chapters will be devoted to discussions of methods and techniques available to forensic scientists to evaluate physical evidence. Although current technology has given the crime laboratory capabilities far exceeding those of past decades, these advances are no excuse for complacency on the part of criminal investigators. Crime laboratories do not solve crimes; only a thorough and competent investigation conducted by professional police officers will enhance the chances for a successful criminal investigation. Forensic science is, and will continue to be, an important element of the total investigative process, but it is only one aspect of an endeavor that must be a team effort. The investigator who believes the crime laboratory to be a panacea for laxity or ineptness is in for a rude awakening.

Forensic science begins at the crime scene. If the investigator cannot recognize physical evidence or cannot properly preserve it for laboratory examination, no amount of sophisticated laboratory instrumentation or technical expertise can salvage the situation. The know-how for conducting a proper crime-scene search for physical evidence is within the grasp of any police department, regardless of its size. With proper training, police agencies can ensure competent performance at crime scenes. In many jurisdictions, police agencies have delegated this task to a specialized team of technicians. However, the techniques of crime-scene investigation are not dif- ficult to master and certainly lie within the bounds of comprehension of the average police officer.

Not all crime scenes require retrieval of physical evidence, and limited resources and personnel have forced many police agencies to restrict their efforts in this area to crimes of a more serious nature. Once the commitment is made to completely process a crime site for physical evidence, however, certain fundamental practices must be followed.

Securing and Isolating the Crime Scene The first officer arriving on the scene of a crime is responsible for preserving and protecting the area as much as possible. The officer should not let his or her guard down and must rely on his or her training to deal with any violent or hazardous circumstances. Special note should be taken of any vehicles or people leaving the scene.

Of course, first priority should be given to obtaining medical assistance for individuals in need of it and to arresting the perpetrator. However, as soon as possible, extensive efforts must be made to exclude all unauthorized personnel from the scene. If medical assistance is needed, the officer should direct medical workers to approach the body by an indirect route to minimize the possibility of disturbing evidence. The first responding officer must evaluate the victim’s con- dition and record any statements made by the victim. This information should later be included in notes.

As additional officers arrive, measures are immediately initiated to isolate the area. See Figure 2–1. 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. Ropes or barricades along with strategic positioning of guards will prevent unauthorized access to the area. Efforts must be taken to identify all individuals at the scene and detain all potential suspects or wit- nesses still at the scene. At the same time, officers should exclude all unauthorized personnel from the scene. This includes family and friends of the victim, who should be shown as much compas- sion as possible. Only investigative personnel assigned to the scene should be admitted. The responding officers 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 more difficult than expected. Violent crimes are especially susceptible to attention from higher-level police officials and members

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FIGURE 2–1 The first investigators to arrive must secure the crime scene and establish the crime-scene perimeter. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com

of the press, as well as by emotionally charged neighbors and curiosity seekers. Every individual who enters the scene is a potential destroyer of physical evidence, even if it is by unintentional care- lessness. To exercise proper control over the crime scene, the officer responsible for protecting it must have the authority to exclude everyone, including fellow police officers 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, trampled through the site. Securing and isolating 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.

Once the scene has been secured, a lead investigator starts evaluating the area. First, he or she determines the boundaries of the scene and then establishes the perpetrator’s path of entry and exit. Logic dictates that obvious items of crime-scene evidence will first come to the attention of the crime-scene investigator. These items must be documented and photographed. The investiga- tor then proceeds with an initial walk-through of the scene to gain an overview of the situation and develop a strategy for systematically examining and documenting the entire crime scene.

Personnel should never do anything while at the crime scene—including smoking, eating, drinking, and littering—that may 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 investigating officers or bystanders. This means that no one should open or close faucets or flush toilets at the scene. Also, officers should avoid altering temperature conditions at the scene by adjusting windows, doors, or the heating or air conditioning.

Recording the Crime Scene Investigators have only a limited amount of time to work a crime site in its untouched state. The opportunity to permanently record the scene in its original state must not be lost. Such records not only will prove useful during the subsequent investigation but are also required for presentation at a trial in order to document the condition of the crime site and to delineate the location of physical evidence. Notes, photography, and sketches are the three methods for crime-scene recording (see Figure 2–2). Ideally all three should be employed; however, personnel and

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monetary limitations often prohibit the use of photography at every crime site. Under these circumstances, departmental guidelines will establish priorities for deploying photographic resources. However, there is no reason not to make sketches and notes at the crime scene.

NOTES The note-taking process begins with the call to a crime-scene investigator to report to a scene. The notes should start by identifying the person who contacted the investigator, the time of the contact, and any preliminary information 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 time of arrival should be recorded. Investigators must keep a precise record of personnel movements in and out of the scene, beginning with an interview of the first responding officer in order to record his or her movements. It is also important to record the tasks assigned to each member of a team, as well as the beginning and ending times for the processing of the scene.

Before the scene is sketched, photographed, or searched, the lead investigator carries out the initial walk-through. During this walk-through, the investigator should take notes on many aspects of the crime scene in its original condition. These notes should be uniform in layout for all 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 memory to record later.

Once a search for evidence has taken place, the team members mark the location of all evidence and fully describe each item in their notes. 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. Any preliminary identification of a victim or suspect should be recorded.

Tape-recording notes at a scene can be advantageous—detailed notes can be taped much faster than they can be written. This may also leave hands free to carry out other tasks while recording the notes. Audiotapes have the added security feature of preventing erasure or taping over if the security tab on the tape is removed. However, care must be taken to avoid embarrass- ing 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

FIGURE 2–2 The finding 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 find in field notes. Courtesy Police Science Services, Niles, Ill.

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by narrating a videotape of the crime scene. This has the advantage of com- bining note-taking with photography. However, at some point the tape must be transcribed into a written document.

PHOTOGRAPHY The most important prerequisite for photographing a crime scene is for it to be unaltered. Unless injured people are involved, objects must not be moved until they have been photographed from all necessary angles. If objects are removed, positions changed, or items added, the photographs may not be admissible as evidence at a trial, and their intended value will be lost. If evidence has been moved or removed before photography, the fact should be noted in the report, but the evidence should not be reintroduced into the scene in order to take photographs.

Crime-scene photographs have great value in their ability to show the layout of the scene, the position of evidence to be collected, and the relation of objects at the scene to one another. Photographs taken from many angles can show possible lines of sight of victims, suspects, or witnesses. An accurate de- scription of the scene must be available to investigators for future analysis. Pho- tography is also important for documenting biological evidence in its original condition, as this kind of evidence is often altered during testing. Photographs cannot stand alone, however, and they are complementary to notes and sketches.

Currently there are two approaches to crime-scene photography: film and digital photography. Obvious differences exist between the ways film and digi- tal imaging technology record scenes, notably the methods by which each type of photography converts light into an image. Photographic film consists of a sheet of light-reactive silver halide grains and comes in several varieties.Adigital photograph is made when a light-sensitive microchip inside the camera is exposed to light coming from the object or scene to be captured. The light is recorded on millions of tiny picture elements, or pixels, as a spe- cific electric charge. The camera reads this charge number as image information, then stores the im- age as a file on a memory card. Most modern crime-scene investigators use a digital camera, such as the digital single-lens reflex camera in Figure 2–3, to document crime scenes, and digital photog- raphy is rapidly becoming the method of choice in the field of forensic science.

The nature of digital images, however, opens digital photography to important criticisms within forensic science casework. Because the photographs are digital, they can be easily manip- ulated by using computer software. This manipulation goes beyond traditional photograph en- hancement such as adjusting brightness and contrast or color balancing. Because the main function of crime-scene photography is to provide an accurate depiction, this is a major concern. To ensure that their digital images are admissible, many jurisdictions set guidelines for deter- mining the circumstances under which digital photography may be used and establish and enforce strict protocols for image security and chain of custody.

Photographic Procedures Each crime scene should be photographed as completely as possible. This means that the crime scene should include the area in which the crime took place and all ad- jacent areas where important acts occurred immediately before or after the commission of the crime. Overview photographs of the entire scene and surrounding area, including points of exit and entry, 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 be taken to show the body’s position and location relative to the entire scene. Close-up photos depicting injuries and weapons lying near the body are also necessary (see Figure 2–4). After the body is removed from the scene, the surface beneath the body should be photographed.

As items of physical evidence are discovered, they are photographed to show their position and location relative to the entire scene. After these overviews are taken, close-ups should be taken to record the details of the object itself. When the size of an item is of significance, a ruler or other measuring scale may be inserted near the object and included in the photograph as a point of refer- ence. The digital revolution promises to bring enhanced photographic capabilities to the crime scene. For example, individual images of the crime scene captured with a digital camera can be stitched together electronically to reveal a near three-dimensional panoramic view of the crime scene (see Figure 2–5).

FIGURE 2–3 An example of a digital single lens reflex (DSLR) camera. Courtesy Sony Electronics Inc.

WEBEXTRA 2.1 Making a Photographic Record of the Crime Scene www.mycrimekit.com

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FIGURE 2–4 This sequence of crime-scene photographs shows the proper progression of photographing the scene. (a) The sequence begins 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.

FIGURE 2–5 Individual images (top) are shown before being electronically stitched together into a single panoramic image (bottom). Individual photographs should be taken with about a 30 percent overlap. Courtesy Imaging Forensics, Fountain Valley, Calif., www.imagingforensics.com

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WEBEXTRA 2.2 Three-Dimensional Crime-Scene Imaging www.mycrimekit.com

FIGURE 2–6 A computer-controlled scanner has both a high-resolution, professional digital camera and a long-range laser rangefinder. 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 3D models of the scene. Courtesy 3rd Tech, Inc., Durham, N.C. 27713, www. deltasphere.com

The digital era promises new and elegant approaches to document the crime scene. Cameras such as that shown in Figure 2–6 are capable of taking dozens of digital images while scanning the crime scene. Photographic and laser data from multiple scan locations 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 Recording The use of videotape or digital video at crime scenes is becoming increasingly pop- ular because the cost of this equipment is decreasing. The same principles used in crime-scene photo- graphs apply to videotaping or digital video. As with conventional photography, videotaping or digital video should include the entire scene and the immediate surrounding area. Long shots as well as close-ups should be taken in a slow and systematic manner. Furthermore, it is desirable to have one crime-scene investigator narrate the events and scenes being recorded while another does the shooting.

Videotaping or digital video can have advantages over still photography in certain situations. For example, modern video cameras allow the user to play back recordings of a scene and check it for completeness. In addition, many video cameras can also take still photographs, or stills can be created from the tape on a computer. Video essentially combines notes and photography. Some cameras even have a “night vision” feature, which is similar to infrared photography.

There are also disadvantages to video recording crime scenes. The camera will always shake, zooming and panning can be sloppy, and extra noise can obscure narration or may be inappro- priate and damaging. Still images taken from video recordings are usually of much poorer qual- ity than those taken by film or digital camera. Videotape, if used, also deteriorates because the tape is sensitive, and it can be affected by high temperatures, humidity, and magnetic fields.

Although video recording can capture the sounds and scenes of the crime site with relative ease, the technique cannot at this time be used in place of still photography. The still photograph remains unsurpassed in the definition of detail it provides to the human eye.

SKETCHES Once photographs have been taken, the crime-scene investigator 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 rela- tionship in space of all the items and features significant to the investigation. Sketches are espe- cially important to illustrate the location of collected evidence. Possible paths of entry, exit, and movement through the scene may be speculated from a good 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 neces- sary is a rough sketch containing an accurate depiction of the dimensions of the scene and showing

rough sketch A draft representation of all essential information and measurements at a crime scene; this sketch is drawn at the crime scene

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finished sketch A precise rendering of the crime scene, usually drawn to scale

34 CHAPTER 2

FIGURE 2–7 A basic kit for sketching the crime scene. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

the location of all objects having a bearing on the case. This may be achieved through the use of a sketching kit like the one shown in Figure 2–7.

A rough sketch is illustrated in Figure 2–8. It shows all recovered items of physical evidence as well as other important features of the crime scene. Objects are located in the sketch by dis- tance measurements from two fixed points, such as the walls of a room. Distances shown on the sketch must be accurate and not the result of a guess or estimate. For this reason, all measure- ments are made with a tape measure. The simplest way to designate an item in a sketch is to as- sign it a number or letter. A legend or list placed below the sketch then correlates the letter to the item’s description. The sketch should also show a compass heading designating north as well as a title block designating the location of the crime scene and any case information.

Unlike the rough sketch, the finished sketch in Figure 2–9 is constructed with care and concern for aesthetic appearance. When the finished sketch is completed, it must reflect information contained within the rough sketch in order to be admissible evidence in a courtroom. Computer-aided drafting (CAD) has become the norm to reconstruct crime scenes from rough sketches. The software, ranging from simple, low-cost programs to complex, expensive programs, contains predrawn intersections and roadways or buildings and rooms onto which information can be entered (see Figure 2–10). Agenerous symbol library provides the operator with 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, computerized sketch- ing can focus on a specific area for a more detailed picture. CAD programs allow the operator to select scale size so that the ultimate product can be produced in a size suitable for courtroom presentation.

Conducting a Systematic Search for Evidence The search for physical evidence at a crime scene must be thorough and systematic. For a factual, unbiased reconstruction of the crime, the investigator, relying on his or her training and experi- ence, must not overlook any pertinent evidence. Even when suspects are immediately seized and the motives and circumstances of the crime are readily apparent, a thorough search for physical evidence must be conducted at once. Failure in this, even though it may seem unnecessary, can lead to accusations of negligence or charges that the investigative agency knowingly “covered up” evidence that would be detrimental to its case.

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FIGURE 2–8 Rough-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.comIS

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FIGURE 2–9 Finished-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

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Assigning those responsible for searching a crime scene is a function of the investigator in charge. Except in major crimes, or when the evidence is complex, the assistance of a forensic sci- entist at the crime scene is usually not necessary; his or her role appropriately begins when evi- dence is submitted to the crime laboratory. As has already been observed, some police agencies have trained field evidence technicians to search for physical evidence at the crime scene. They have the equipment and skill to photograph the scene and examine it for the presence of finger- prints, footprints, tool marks, or any other type of evidence that may be relevant to the crime.

SEARCH PATTERNS How one conducts 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. When possible, one person should supervise and coordinate the collection of evidence. Without proper control, the search may be conducted in an atmosphere of confusion with needless duplication of effort. The various search patterns that may be used can be observed in Figure 2–11.

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FIGURE 2–10 Construction of a crime-scene diagram with the aid of a computer-aided drafting program. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

Grid search

Quadrant or zone search

end

start

Spiral search method(c)(b)

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Strip or line search(a)

FIGURE 2–11 (a) Strip or line search pattern. (b) Grid search pattern. (c) Spiral search pattern. (d) Wheel or ray search pattern. (e) Quadrant or zone search pattern.

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Strip or Line Search Pattern In the line or strip method, 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 lit- tle farther along the border and walk straight back to the other side. This method is best used in scenes where the boundaries are well established because the boundaries dictate the beginning and end of the search lines. If the boundary is incorrectly chosen, important evidence may remain undiscovered outside the search area.

Grid Search Pattern The grid method employs two people performing line searches that origi- nate from adjacent corners and form perpendicular lines. This method is very thorough, but the boundaries must be well established in order to use this method as well.

Spiral Search Pattern The spiral search pattern usually employs one person. The investigator moves either in an inward spiral from the boundary to the center of the scene or in an outward spiral from the center to the boundary. 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. With either spiral approach the searcher can easily locate footprints leading away from the scene in any direc- tion. However, completing a perfect spiral is often difficult, and evidence could be missed.

Wheel or Ray Search Pattern The wheel or ray method employs several 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.

Quadrant or Zone Search Pattern The quadrant or zone method divides 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. This method is best suited for scenes that cover a large area. The areas searched must include all probable points of entry and exit used by the criminals.

LOCATING PHYSICAL EVIDENCE What to search for will be determined by the particular circumstances of the crime. Obviously, the skill of crime-scene investigators at recognizing evidence and searching relevant locations is paramount to successful processing of the crime scene. Although training will impart general knowledge for conducting a proper crime-scene investigation, ultimately the investigator must rely on experience gained from numerous investi- gations to form a successful strategy for recovering relevant physical evidence.

For example, in a homicide case, the search will center on the weapon and any evidence left as a result of contact between the victim and the assailant. The cross-transfer of evidence, such as hairs, fibers, and blood, between individuals involved in the crime is particularly useful for linking suspects to the crime scene and for corroborating events that transpired during the commission of the crime. During the investigation of a burglary, efforts will be made to locate tool marks at the point of entry. In most crimes, a thorough and systematic search for latent fingerprints is required.

Vehicle searches must be carefully planned and systematically carried out. The nature of the case determines how detailed the search must be. In hit-and-run cases, the outside and undercar- riage of the car must be examined with care. Particular attention is paid to looking for any evidence resulting from a cross-transfer of evidence between the car and the victim—this in- cludes blood, tissue, hair, fibers, and fabric impressions. Traces of paint or broken glass may be located on the victim. In cases of homicide, burglary, kidnapping, and so on, all areas of the vehicle, inside and outside, are searched with equal care for physical evidence.

Collecting and Packaging Physical Evidence Physical evidence can be anything from massive objects to microscopic traces. Often, many items of evidence are obvious in their presence, 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 fibers may be revealed in vacuum sweepings or on garments only after close laboratory scrutiny. For this reason, it is im- portant to collect possible carriers of trace evidence in addition to more discernible items. Hence, it may be necessary to take custody of all clothing worn by the participants in a crime.

COLLECTING PHYSICAL EVIDENCE Each clothing item should be handled carefully and wrapped separately to avoid loss of trace materials. Critical areas of the crime scene should be

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vacuumed and the sweepings submitted to the laboratory for analysis. The sweepings from different areas must be collected and packaged separately. A portable vacuum cleaner equipped with a special filter attachment is suitable for this purpose (see Figure 2–12). Additionally, fin- gernail scrapings from individuals who were in contact with other individuals may contain minute fragments of evidence capable of linking the assailant and victim. The undersurface of each nail is best scraped with a dull object such as a toothpick to avoid cutting the skin. These scrapings will be subjected to microscopic examination in the laboratory.

The search for physical evidence must extend beyond the crime scene to the autopsy room of a deceased victim. Here, the medical examiner or coroner carefully examines the victim to establish a cause and manner of death. Tissues and organs are routinely 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 to be collected and sent to the forensic laboratory:

1. Victim’s clothing 2. Fingernail scrapings 3. Head and pubic hairs 4. Blood (for DNA typing purposes) 5. Vaginal, anal, and oral swabs (in sex-related crimes) 6. Recovered bullets from the body 7. Hand swabs from shooting victims (for gunshot residue analysis)

Once the body is buried, efforts at obtaining these items may prove difficult or futile. Furthermore, a lengthy time delay in obtaining many of these items will diminish or destroy their forensic value.

In recent years, many police departments have gone to the expense of purchasing and equip- ping “mobile crime laboratories” (see Figure 2–13) for their evidence technicians. However, the term mobile crime laboratory is a misnomer. These vehicles carry the necessary supplies to protect the crime scene; photograph, collect, and package physical evidence; and 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 appropriate but perhaps less dramatic name for such a vehicle.

HANDLING EVIDENCE Investigators must handle and process physical evidence in a way that prevents any change from taking place 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 contamina- tion, breakage, evaporation, accidental scratching or bending, or improper or careless packaging.

FIGURE 2–12 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 filter 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 filter paper is removed and retained for laboratory examination. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

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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 collecting 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 found at the crime site. Whenever possible, one should submit evidence to the laboratory intact. The investigator normally should not remove blood, hairs, fibers, soil particles, and other types of trace evidence from garments, weapons, or 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. Use common sense when handling evidence adhering to a large structure, such as a door, wall, or floor; remove the specimen with a forceps or other appropriate tool. In the case of a bloodstain, one 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. For- ceps and similar tools may be used to pick up small items. Unbreakable plastic pill bottles with pressure lids are excellent containers for hairs, glass, fibers, and various other kinds of small or trace evidence. Alternatively, manila envelopes, screw-cap glass vials, sealable plastic bags, or metal pillboxes are adequate containers for most trace evidence encountered at crime sites (see Figure 2–14). Charred debris recovered from the scene of a suspicious fire must be sealed in an

PO L ICE

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FORENSIC KIT STORAGE

SINK

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FIGURE 2–13 Inside view of a mobile crime-scene van: (a) driver’s side and (b) passenger’s side. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com

POL ICE GENERATOR

COMPARTMENT

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airtight container to prevent the evaporation of volatile petroleum residues. New paint cans or tightly sealed jars are recommended in such situations (see Figure 2–15).

One should not use ordinary mailing envelopes as evidence containers because powders and fine particles will leak out of their corners. Instead, small amounts of trace evidence can be con- veniently packaged in a carefully folded paper, using what is known as a “druggist fold” (see Figure 2–16). This consists of folding one end of the paper over by one-third, then folding the other end (one-third) over that, and repeating the process from the other two sides. After folding the paper in this manner, tuck the outside two edges into each other to produce a closed container that keeps the specimen from falling out.

Place each different item or similar items collected at different locations in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

Biological Materials Use only disposable tools to collect biological materials for packaging. If biological materials are stored in airtight containers, the accumulation of moisture may

FIGURE 2–14 (a) Manila evidence envelope. (b) Metal pillboxes. (c) Sealable plastic evidence bag. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

(a)

(b) (c)

FIGURE 2–15 Airtight metal cans used to package arson evidence. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

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encourage the growth of mold, which can destroy the evidential value of blood. In these instances, wrapping paper, manila envelopes, or paper bags are recommended packaging materials (see Figure 2–17). As a matter of routine, air-dry all items possibly containing biological fluid evidence and place them individually in separate paper bags to ensure a constant circulation of air through them. This will prevent the formation of mold and mildew. Paper packaging is easily written on, but seals may not be sturdy.

The evidence collector must handle all body fluids and biologically stained materials with a minimum of personal contact. All body fluids must be assumed to be infectious, so investigators must wear disposable latex gloves while handling the evidence. Latex gloves also significantly reduce the possibility that the evidence collector will contaminate the evidence. Investigators should change gloves frequently while collecting evidence. Safety considerations and avoidance of contamination also dictate that evidence collectors wear face masks and shoe covers.

DNA Evidence The advent of DNA analysis is one of the most significant recent advances in crime-scene investigation. This technique is valuable in its ability to identify suspects by detect- ing and analyzing minute quantities of DNA deposited on evidence as a result of contact with saliva, sweat, or skin cells. The search for evidence should include all objects with which the suspect or victim may have come into bodily contact because DNA evidence may be present on the object. Likely sources of DNA evidence include stamps and envelopes licked with saliva, 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.

FIGURE 2–16 A druggist fold is used to package paint transfer evidence. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

FIGURE 2–17 Paper bags are recommended evidence containers for objects suspected of containing blood and semen stains. Each object should be packaged in a separate bag. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

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One key concern during the collection of a DNA-containing specimen is contamination. Contamination can occur by introducing foreign DNA through 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. The evidence collector must take extraordinary care to avoid potential contamination from transferring DNA onto objects of evidential value. 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 wear- ing coveralls and shoe covers as an extra precaution to avoid contaminating DNA evidence.

Blood has great evidential value when the investigator can 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 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.

Proper collection and packaging of various types of physical evidence will be discussed in detail in forthcoming chapters; additionally, most of this information is summarized in the evidence guide found in Appendix I.

Maintaining the Chain of Custody Continuity of possession, or the chain of custody, must be established whenever evidence is presented in court as an exhibit. Adherence to standard procedures in recording the location of evidence, marking it for identification, and properly completing evidence submission forms for laboratory analysis is the best guarantee that the evidence will withstand inquiries of what happened to it from the time of its finding to its presentation in court. This means that every person who handled or examined the evidence must be accounted for. Failure to substantiate the evidence’s chain of custody may lead to serious questions regarding the authenticity and integrity of the evidence and examinations of it.

All items of physical evidence should be carefully packaged and marked upon their retrieval at crime sites. This should be done with the utmost care to avoid destroying their evidential value or restricting the number and kind of examinations to which the criminalist may subject them. If possible, the evidence itself should be marked for identification. Normally, the collector’s initials and the date of collection are inscribed directly on the article. However, if the evidence collector is unsure of the necessity of marking the item itself or of where to mark it, it is best to omit this step. Once an evidence container is selected for the evidence, whether a box, bag, vial, or can, it also must be marked for identification. Evidence containers often have a preprinted identification form that the evidence collector fills out. Otherwise, the collector must attach an evidence tag to the container. 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 observa- tion at a later time should try to avoid breaking the original seal if possible so that the informa- tion 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.

A minimum chain-of-custody record would show the collector’s initials, location of the evidence, and date of collection. If the evidence is turned over to another individual for care or delivery to the laboratory, this transfer must be recorded in notes and other appropriate forms. In fact, every individual who possesses the evidence must maintain a written record of its acquisi- tion and disposition. Frequently, all of the individuals involved in the collection and transporta- tion of the evidence may be requested to testify in court. Thus, to avoid confusion and to retain complete control of the evidence at all times, the chain of custody should be kept to a minimum.

Obtaining Standard/Reference Samples The examination of evidence, whether soil, blood, glass, hair, fibers, and so on, often requires com- parison with a known standard/reference sample. Although most investigators have little diffi- 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 mate- rials. Such materials may be obtained from the victim, a suspect, or other known sources. For in- stance, investigation of a hit-and-run incident may require the removal of standard/reference paint from a suspect vehicle. This will permit its comparison to paint recovered at the scene. Similarly, hair found at the crime scene will be of optimum value only when compared to standard/reference

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

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

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substrate control Uncontaminated surface material close to an area where physical evidence has been deposited; this sample is to be used to ensure that the surface on which a sample has been deposited does not interfere with laboratory tests

buccal swab A swab of the inner portion of the cheek; cheek cells are usually collected to determine the DNA profile of an individual

44 CHAPTER 2

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 determine the evidential value of crime-scene evidence, and these standard/reference specimens must be treated with equal care.

Some types of evidence must also be accompanied by the collection of substrate controls. These are materials adjacent or close to areas where physical evidence has been deposited. For example, substrate controls are normally collected at arson scenes. If an investigator suspects that a particular surface has been exposed to gasoline or some other accelerant, the investigator should also collect a piece of the same surface material that is believed not to have been exposed to the accelerant. At the laboratory, the substrate control is tested to ensure that the surface on which the accelerant was deposited does not interfere with testing procedures. Another common example of a substrate control is a material on which a bloodstain has been deposited. Unstained areas close to the stain may be sampled for the purpose of determining whether this material will have an impact on the interpretation of laboratory results.

Thorough collection and proper packaging of standard/reference specimens and substrate controls are the mark of a skilled investigator.

Submitting Evidence to the Laboratory Evidence is usually submitted to the laboratory either by personal delivery or by mail shipment. The method of transmittal is determined by the distance the submitting agency must travel to the laboratory and the urgency of the case. If the evidence is delivered personally, the deliverer should be familiar with the case, to facilitate any discussions between laboratory personnel and the deliverer concerning specific aspects of the case.

If desired, most evidence can be conveniently shipped by mail. However, postal regulations restrict the shipment of certain chemicals and live ammunition and prohibit the mailing of explosives. In such situations, the laboratory must be consulted to determine the disposition of these substances. Care must also be exercised in the packaging of evidence in order to prevent breakage or other accidental destruction while it is in transit to the laboratory.

Most laboratories require that an evidence submission form accompany all evidence submit- ted. One such form is shown in Figure 2–18. This form must be properly completed. Its information will enable the laboratory analyst to make an intelligent and complete examination of the evidence. Particular attention should be paid to providing the laboratory with a brief description of the case history. This information will allow the examiner to analyze the specimens in a logical sequence and make the proper comparisons, and it will also facilitate the search for trace quantities of evidence.

The particular kind of examination requested for each type of evidence is to be delineated. However, the analyst will not be bound to adhere strictly to the specific tests requested by the investigator. As the examination proceeds, new evidence may be uncovered, and as a result the complexity of the case may change. Furthermore, the analyst may find the initial requests in- complete or not totally relevant to the case. Finally, a list of items submitted for examination must be included on the evidence submission form. Each item is to be packaged separately and as- signed a number or letter, which should be listed in an orderly and logical sequence on the form.

Ensuring Crime-Scene Safety The increasing spread of AIDS and hepatitis B has sensitized the law enforcement community to the potential health hazards at crime scenes. Law enforcement officers have an extremely small chance of contracting AIDS or hepatitis at the crime scene. Both diseases are normally transmit- ted by the exchange of body fluids, such as blood, semen, and vaginal and cervical secretions; intravenous drug needles and syringes; and transfusion of infected blood products. However, the presence of blood and semen at crime scenes presents the investigator with biological specimens of unknown origin; the investigator has no way of gauging what health hazards they may contain. Therefore, caution and protection must be used at all times.

Fortunately, inoculation can easily prevent hepatitis B infection in most people. Furthermore, the federal Occupational Safety and Health Administration (OSHA) requires that law enforce- ment agencies offer hepatitis B vaccinations to all officers who may have contact with body fluids while on the job, at no expense to the officer.

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FIGURE 2–18 An example of a properly completed evidence submission form.

The International Association for Identification Safety Committee has proposed the follow- ing guidelines to protect investigators at crime scenes containing potentially infectious materials:

1. Forensic and crime-scene personnel may encounter potentially infectious materials, such as in the case of a homicide, in which blood or body fluids may be localized to the area of the body or dispersed throughout the crime scene. At such scenes, it is recommended that per- sonnel wear a minimum of latex gloves (double gloved) and protective (Tyvek-type) shoe covers. In cases of large contamination areas, liquid repellent coveralls (Tyvek or Kleengard suits) are recommended along with the gloves and shoe covers.

2. The use of a particle mask/respirator, goggles, or face shield is recommended in addition to the protective items listed in item 1 when potentially infectious dust or mist may be encoun- tered at the crime scene. This includes collection of dried bloodstains by scraping; collection,IS

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folding, and preservation of garments that may be contaminated with blood or body fluids, especially if they are in a dried state; and application of aerosol chemicals to bloodstains or prints for their detection and/or enhancement.

3. When processing and collecting evidence at a crime scene, personnel should be alert to sharp objects, knives, hypodermic syringes, razor blades, and similar items. If such sharp objects are encountered and must be recovered as evidence, the items should be placed in an appro- priate container and properly labeled. When conventional latent-print powder techniques are used in or around areas contaminated with blood, a specific brush should be designated so that it can be subsequently decontaminated or appropriately disposed of after processing is complete. If latents are developed in or around blood-contaminated areas, they should be photographed, or lifted and placed in a sealed plastic bag. The sealed bag then should be affixed with an appropriate biohazard label.

Evidence collected for transport should be packaged to maintain its integrity and to pre- vent contamination of personnel or personal items. Evidence contaminated with wet blood should first be placed in a paper bag and then temporarily stored in a red biohazard plastic bag for immediate transport to an appropriate drying facility.

4. When potentially infectious materials are present at a crime scene, personnel should main- tain a red biohazard plastic bag for the disposal of contaminated gloves, clothing, masks, pen- cils, 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.

5. Note taking should be done while wearing uncontaminated gloves to avoid contamination of pens, pencils, notebook, paper, and so on. Pens or markers used to mark and package con- taminated evidence should be designated for proper disposal in a red biohazard bag before investigators leave the crime scene.

6. If individual protective equipment becomes soiled or torn, it must be removed immediately. Personnel must then disinfect/decontaminate the potentially contaminated body areas using a recommended solution, such as a 10 percent bleach solution, or an antimicrobial soap or towelette. After cleansing, the area must be covered with clean, replacement protective equipment. On departure from the scene, this procedure should be repeated on any body area where contamination could have occurred.

7. Eating, drinking, smoking, and application of makeup are prohibited at the immediate crime scene.

8. All nondisposable items, such as lab coats, towels, and personal clothing, that may be contam- inated with potentially infectious material should be placed in a yellow plastic bag labeled “In- fectious Linen” and laundered, at the expense of the employer, by a qualified laundry service. Personal clothing that may have been contaminated should never be taken home for cleaning.

Legal Considerations at the Crime Scene In police work, perhaps no experience is more exasperating or demoralizing than to see 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. There- fore, removal of any evidence from a person or from the scene of a crime must be done in con- formity with Fourth Amendment privileges: “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizure, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particu- larly describing the place to be searched, and the persons or things to be seized.”

Since the 1960s, the Supreme Court has been particularly concerned with defining the cir- cumstances under which the police can search for evidence in the absence of a court-approved search warrant. A number of allowances have been made 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 pro- vided it is made incident to a lawful arrest, and (4) a search made by consent of the parties in- volved. In cases other than these, police must be particularly cautious about processing a crime scene without a search warrant. In 1978, the Supreme Court addressed this very issue and in so doing set forth guidelines for investigators to follow in determining the propriety of conducting

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a warrantless search at a crime scene. Significantly, the two cases decided on this issue related to homicide 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 sus- pected of dealing drugs. Under the pretext of buying drugs, an undercover police officer forced entry into Mincey’s apartment and was killed in a scuffle 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 officers 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 homi- cide 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 indication 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 a business establishment leased by Loren Tyler and a business partner was destroyed by fire. The fire was finally extinguished in the early hours of the morning; how- ever, hampered by smoke, steam, and darkness, fire officials and police were prevented from thor- oughly examining the scene for evidence of arson. The building was then left unattended until eight A.M. of that day, when officials returned and began an inspection of the burned premises. During the morning search, assorted items of evidence were recovered and removed from the building. On three other occasions—four days, seven days, and twenty-five days after the fire— investigators reentered the premises and removed additional items of evidence. Each of these searches was made without a warrant or without consent, and the evidence seized was used to con- vict Tyler and his partner of conspiracy to burn real property and related offenses. The Supreme Court upheld the reversal of the conviction, holding the initial morning search to be proper but contending that evidence obtained from subsequent reentries to the scene was inadmissible: “We hold that an entry to fight a fire requires no warrant, and that once in the building, officials may remain there for a reasonable time to investigate the cause of a blaze. Thereafter, additional entries to investigate the cause of the fire must be made pursuant to the warrant procedures.”

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

chapter summary

Physical evidence includes all objects that can establish or dis- prove that a crime has been committed or can link a crime and its victim or its perpetrator. Forensic science begins at the crime scene. Here, investigators must recognize and properly preserve evidence for laboratory examination. The first officer

to arrive is responsible for securing the crime scene. Once the scene is secured, relevant investigators record the crime scene by using photographs, sketches, and notes. Before processing the crime scene for physical evidence, the investigator should make a preliminary examination of the scene as it was left by

1437 U.S. 385 (1978). 2436 U.S. 499 (1978).

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the perpetrator. The search for physical evidence at a crime scene must be thorough and systematic. The search pattern selected normally depends on the size and locale of the scene and the number of collectors participating in the search.

Physical evidence can be anything from massive objects to microscopic traces. Often, many items of evidence are clearly visible, but others may be detected only through exam- ination at the crime laboratory. For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fingernail scrapings, in addition to more discernible items. Each different item or similar items

collected at different locations must be placed in a separate container. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

During the collection of evidence, the chain of custody, a record for denoting the location of the evidence, must be main- tained. In addition, proper standard/reference samples, such as hairs, blood, and fibers, must be collected at the crime scene and from appropriate subjects for comparison in the labora- tory. The removal of any evidence from a person or from the scene of a crime must be done in accordance with appropriate search and seizure protocols.

review questions

1. The term ___________ encompasses all objects that can establish or disprove whether a crime has been commit- ted or can link a crime and its victim or its perpetrator.

2. True or False: Scientific evaluation of crime-scene evidence can usually overcome the results of a poorly conducted criminal investigation. ___________

3. True or False: The techniques of physical evidence collection require a highly skilled individual who must specialize in this area of investigation. ___________

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

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

6. 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 this person must rely on his or her training to deal with any violent or hazardous circumstances.

7. At a crime scene, first priority should be given to obtaining ___________ for individuals in need of it and attempting to minimize disturbance of evidence.

8. True or False: The boundaries of the crime scene, de- noted by crime-scene tape, rope, or traffic cones, should encompass only the center of the scene where the crime occurred. ___________

9. Even though no unauthorized personnel are admitted to the scene, an accurate ___________ must be kept of those who do enter and exit the scene and the time they do so.

10. True or False: The lead investigator will immediately proceed to gain an overview of the situation and develop a strategy for the systematic examination of the crime scene during the final survey. ___________

11. Three methods for recording the crime scene are ___________, ___________, and ___________.

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

13. The crime-scene notes should include a precise record of personnel movements in and out of the scene starting with the ___________.

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

15. Before located evidence is collected, it must be fully described in the investigator’s ___________.

16. 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. ___________

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

18. Photographs of physical evidence must include overviews as well as ___________ to record the details of objects.

19. True or False: The value of crime-scene photographs lies in their ability to show the layout of the scene, po- sition of witnesses, and relation of people to one another in the scene. ___________

20. The most commonly used camera for crime-scene pho- tography is the ___________ camera, which can be film or digital.

21. A digital camera captures light on a light-sensitive ___________.

22. True or False: Each crime scene should be pho- tographed as completely as possible in a logical succes- sion and the photographs should include the area in which the crime actually took place and all adjacent ar- eas where important acts occurred. ___________

23. The succession of photographs taken at a crime scene is ___________ photographs first and ___________ pho- tographs last.

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

25. 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.

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26. The process of ___________ the crime scene essentially combines notes and photography.

27. Unlike the rough sketch, the ___________ is constructed with care and concern for aesthetic appearance and must be drawn to scale.

28. ___________ programs provide an extensive symbol library and may create a three-dimensional sketch.

29. An investigator need only draw a(n) ___________ sketch at the crime scene to show its dimensions and per- tinent objects.

30. A detailed search of the crime scene for physical evi- dence must be conducted in a(n) ___________ manner.

31. The crime-scene search is undertaken to locate ___________.

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

33. True or False: If the investigator does not recognize physical evidence or does not properly preserve it for laboratory examination, sophisticated laboratory instru- mentation or technical expertise can salvage the situation and attain the desired results. ___________

34. Besides the more obvious items of physical evidence, possible ___________ of trace evidence must be col- lected for detailed examination in the laboratory.

35. Whenever possible, trace evidence (is, is not) to be removed from the object that bears it.

36. Each item collected at the crime scene must be placed in a(n) ___________ container.

37. True or False: An ordinary mailing envelope is consid- ered a good general-purpose evidence container. ___________

38. An airtight container (is, is not) recommended packag- ing material for bloodstained garments.

39. As a matter of routine, all items of clothing are to be ___________ before packaging.

40. True or False: Charred debris recovered from the scene of an arson is best placed in a porous container. ___________

41. The possibility of future legal proceedings requires that a(n) ___________ be established with respect to the pos- session and location of physical evidence.

42. Most physical evidence collected at the crime scene will require the accompanying submission of ___________ material for comparison purposes.

43. In the case of Mincey v. Arizona, the Supreme Court restricted the practice of conducting a(n) ___________ search at a homicide scene.

44. In the case of Michigan v. Tyler, the Supreme Court dealt with search and seizure procedures at a(n) ___________ scene.

1. You are the first officer at the scene of an outdoor assault. You find 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 fleeing 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-defined boundaries

b. Several people searching a large area

c. A single person searching a large area

3. Officer Bill Walter arrives at the scene of an apparent murder: a body bearing several gunshot wounds lies on the floor of a small, unair-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 Officer Walter make in his investiga- tion? What conclusion did he draw about the scene from his observations?

4. Officer Martin Guajardo is the first responder at an apparent homicide scene. After securing the area, inter- viewing 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, with a small scrap of bloody cloth clinging precariously to the knife. Because it is a very windy day, Officer Guajardo removes the scrap of fabric and seals it in a plastic bag. A few moments later, a crime- scene team, including a photographer, arrives to take over the investigation. What mistakes, if any, did Officer Guajardo make before the crime-scene team arrived?

5. 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 delivers the shirt to the laboratory

application and critical thinking

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Investigators looking into the kidnapping and murder of DEA special agent Enrique Camarena and DEAsource 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 even- tually enabled investigators to solve the case.

1. What were the main challenges facing investigators who were collecting evidence in the case? Give specific examples of these challenges.

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

3. Explain how investigators used reference samples to determine that the victims’ bodies had been buried and later moved to the site where they were discovered. Also explain how they used such evidence to determine the original burial place.

case analysis

with an evidence submission form. There, a forensic sci- entist 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 mis- takes, if any, were made in handling the shirt?

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

Geberth, Vernon J., Practical Homicide Investigation: Tactics, Procedures, and Forensic Techniques, 4th ed. Boca Raton, Fla.: Taylor & Francis, 2006.

Nickell, J., and J. F. Fischer, Crime Scene: Methods of Forensic Detection. Lexington: University Press of Kentucky, 1999.

Ogle, R. R., Jr., Crime Scene Investigation and Reconstruc- tion, 2nd ed. Upper Saddle River, N.J.: Prentice Hall, 2007.

Osterburg, James W., and Richard H. Ward, Criminal Investigation—A Method for Reconstructing the Past, 5th ed. Cincinnati, Ohio: Anderson, 2007.

further references

G A

DOOR

W IN

D OW

A—Dining room table B—Chair C—Overturned chair D—0.38 Revolver E—Male body F—Table G—Chair

DINING ROOM

Sketch by Officer John Smith

2741 Aragon St. 9/6/06

B B C

B BB W IN

D OW

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On February 7, 1985, U.S. Drug Enforcement Agency (DEA) Special Agent (SA) Enrique Camarena was abducted near the U.S. 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.

Throughout this lengthy investigation, unusual forensic problems arose that required unusual solutions. Eventually, numerous suspects were arrested, both in the United States and Mexico, which culminated in an 8-week trial held in U.S. District Court in Los Angeles, CA.

The Abduction On February 7, 1985, SA Camarena left the DEA Resident Office to meet his wife for lunch. On this day, a witness observed a man being forced into the rear seat of a light- colored compact car in front of the Camelot Restaurant and provided descriptions of sev- eral 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 traffickers, Rafael Caro-Quintero and Ernesto Fonseca, were quickly developed as suspects. A short time later at the Guadalajara Airport, as Caro-Quintero and his men attempted to flee by pri- vate jet, a confrontation developed between Caro-Quintero’s men, the MFJP, and DEA agents. After some discussion, Caro-Quintero and his men were permitted to board and leave. It was later learned that a 6-figure bribe had been paid to Pavon-Reyes to allow this departure.

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 U.S. government to accelerate the investigation. High-level U.S. government officials, as well as their Mexican counterparts, were becoming directly involved in the case. It is believed that because of this “heat,” the Mexican drug traffickers and certain Mexican law enforcement officials 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 notified and the case would be closed. Thus, the Bravo gang would provide an easy scapegoat.

During early March, MFJP officers raided the Bravo ranch before the DEA agents arrived. In the re- sulting shootout, all of the gang members, as well as one MFJP officer, 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. The individuals paid to do this job simply left them by the side of a road near the ranch. It was later learned that certain Mexican law enforcement officials were paid a large sum of money to formulate and carry out this plan in order to obstruct and prematurely conclude the investigation.

Shortly after this shootout, a passerby found two partially decomposed bodies, wrapped in plas- tic bags, along a road near the Bravo ranch. 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.

Case Study

The Enrique Camarena Case: A Forensic Nightmare

Michael P. Malone Special Agent, Laboratory Division Federal Bureau of Investigation, Washington, D.C.

Undated photo of Enrique Camarena. Courtesy AP Wide World Photos

Reprinted from FBI Law Enforcement Bulletin, September 1989.

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On March 7, 1985, the FBI dispatched a forensic team to Guadalajara. They immediately proceeded to the morgue to iden- tify the bodies and to process any evidence which might be pres- ent. After much bureaucratic delay from the local officials, they were finally allowed to proceed. The bodies were identified only as cadavers number 1 and number 2. It was apparent that each body had been autopsied and that both were in an advanced state of decomposition. Cadaver number 1 was quickly identified by the fingerprint expert as that of SA Camarena. Mexican officials would not allow the second body to be identified at this time; however, it was later identified through dental records as Captain Zavala.

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.

A forensic pathologist from the Armed Forces Institute of Pathology was allowed to examine the body of SA Camarena. He concluded that SA Camarena’s death was caused by blunt-force injuries. In addition, SA Camarena had a hole in his skull caused by a rod-like instrument. SA Camarena’s body was then released to the American officials and immediately flown to the United States.

The next day, both 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, contami- nated by both police personnel and onlookers, only a limited crime-scene search was conducted. It was immediately noted that there was no grave site 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 sam- ples from the drop site were taken to compare with soil removed from the victims. It was also noted that there were no significant body fluids at the “burial” site. This led the forensic team to con- clude that the bodies had been buried elsewhere, exhumed, and transported to this site.

The MFJP officials were later confronted with the evidence that the bodies had been relocated to the Michoacan area. This was one of the factors which led to a new, unilateral MFJP inves- tigation. As a result, several suspects, including State Judicial Po- lice Officers, were arrested and interrogated concerning the kidnapping of SA Camarena. Primer Comandante Pavon-Reyes was fired, and arrest warrants were issued for a number of inter- national drug traffickers, including Rafael Caro-Quintero and Ernesto Fonseca.

In late March 1985, DEA agents located a black Mercury Gran Marquis which 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 deal- ership 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, fiber, blood, and/or fingerprint 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. The DEA was also informed that since the abduction of SA Camarena, all of the interior walls had been painted, the entire residence had recently been cleaned, and that a group of MFJP officers were presently occupying, and thereby contaminating, the residence.

On the first day after the arrival of the FBI forensic team, they surveyed and began a crime scene search of the residence and surrounding grounds. The residence consists 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 out- building located to the rear of the main residence. This outbuild- ing, designated as the “guest house,” consisted of a small room, carpeted by a beige rug, with an adjoining bathroom. The entire room and bathroom were processed for hairs, fibers, and latent fingerprints. The single door into this room was made of steel and reinforced by iron bars. It was ultimately determined by means of testimony and forensic evidence that several individu- als interrogated and tortured SA Camarena in this room. In addi- tion, a locked bedroom, located on the second floor 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 VW Atlantic, which fit the general description of the smaller vehicle noted by the person who witnessed SA Camarena’s abduction, was parked under a carport at the rear of the residence. The VW Atlantic was also processed for hairs, fibers, and fingerprints.

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. Upon closer inspection, it appeared to be a folded license plate, at the bottom of the drain. However, a heavy iron grate covered the drain and prevented the plate’s immediate retrieval.

When one of the FBI agents returned to the main house to ask the MFJP officers for a crowbar, they became extremely curious and followed the agent as he returned, empty handed, to the ten- nis court. By this time, a second agent had managed to remove the grate by using a heavy-wire coat hanger. The license plate was retrieved, unfolded, and photographed. The MFJP officers, 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. After his arrival approximately 20 minutes later, he seized the license plate and would not allow the Americans to conduct any further searches.

However, by this time, five very large plastic bags of evidence had been recovered and were placed in the rear of a DEA truck. The evidence was quickly transported to the DEA vault in the U.S. Consulate.

After negotiations between the United States and Mexico, the MFJP did allow a second, final search of the residence. On June 24, 1985, a forensic team returned and processed the four remaining rooms on the first floor of the main house.

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By this point in the investigation, an associate of Rafael Caro- Quintero had been arrested and interrogated by the MFJP. He stated that the bodies of two Americans, Albert Radelat and John Walker, who had been abducted and killed by Mexican drug traffickers, were buried on the south side of La Primavera Park, a large, primitive park west of Guadalajara. The bodies of Radelat and Walker were located and recovered. Soil samples taken from the surface of an area near their graves were similar in most respects to the soil recovered earlier from the bodies of SA Camarena and Captain Zavala.

In September 1985, DEA personnel went to La Primavera Park and sampled an area approximately 2 feet below the surface near the same site. This sample matched the soil samples from SA Camarena and Captain Zavala almost grain for grain, indicating 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 U.S. and the Mexican governments, permission was finally 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 SACamarena, 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 trafficker 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 ar- rested by the DEA. He was then transported to Washington, D.C., where hair samples were taken. He refused to testify before a federal grand jury investigating the Camarena case. Later that year, DEA personnel obtained hair samples in Mexico City from Sergio Espino-Verdin, a former federal comandante, who is believed to have been SA Camarena’s primary interrogator during his ordeal at 881 Lope De Vega.

The Trial In July 1988, the main trial of the murder, interrogation, and abduction of SA Camarena began in U.S. District Court in Los Angeles, CA. The forensic evidence presented in this trial identified 881 Lope De Vega as the site where SA Camarena had been held. [See Figure 1.] 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 Gran Marquis, and two types of polyester rug fibers, a dark, rose-colored fiber and a light- colored fiber. [See Figures 2 and 3.] Fabric evidence was also presented, which demonstrated the similarities of color, com- position, construction, 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 tes- tify that SA Camarena was at this residence, as well as in the VW Atlantic and the Mercury Gran 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 associ- ated with the “guest house” at 881 Lope De Vega. Light- colored nylon rug fibers, found on samples of his clothing taken at the second autopsy, matched the fibers 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 20 trial charts were also pre- pared 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, fiber, fabric, and cordage evidence. [See Figure 5.]

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FIGURE 1 Diagram of the 881 Lope De Vega grounds. Camarena was held prisoner in the guest house.

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

Swimming Pool

Storage

GUEST ROOM

MAID’S ROOM

BA TH

Storage

KITCHEN MAIN HOUSE

FRONT PORCH

Co ve

re d

Po rc

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GARAGE Area

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FIGURE 2 Trial chart showing hair comparisons between known Camarena hairs and hairs recovered from 881 Lope De Vega.

FIGURE 3 Trial chart showing hair comparisons between known Camarena hairs and hairs recovered from the Mercury Gran Marquis.

FIGURE 4 A model of 881 Lope De Vega prepared as a trial exhibit.

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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.

FIGURE 5 Trial chart used to show the association of Camarena and Zavala with various locations.

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Conclusion The forensic pitfalls and problems in this case (i.e., destruction of evidence, contamination of crime scenes) were eventually resolved. In some cases, certain routine procedures had to be ig- nored or unconventional methods employed. However, in many instances, detailed trial testimony overcame the limitations of

certain evidence, and eventually, almost all of the evidence in- troduced at the trial made a tremendous impact on the outcome of this proceeding. After an 8-week trial, conducted under tight security and involving hundreds of witnesses, all of the defen- dants were found guilty, convicted on all counts, and are cur- rently serving lengthy sentences.

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Scott Peterson: A Case of Circumstantial Evidence

On the surface, Scott Peterson and his wife, Laci, appeared to live a happy and contented lifestyle in Modesto, California. The 30-year-old Peterson and his 27-year-old former college sweetheart, a substitute teacher, were expecting their first child in about one month when Laci suddenly disappeared. Scott Peterson told investigators that he had last seen his wife on December 24, 2002, at 9:30 A.M. when he left home for a fishing trip off San Francisco Bay.

In April 2003, Laci’s decomposed remains washed ashore not far from where Scott said he had gone fishing on the day she vanished. Peterson

claimed that Laci was dressed in a white top and black pants when he last saw her,

but when her body was found she was wearing khaki pants. Scott’s sister recalled that Laci was wearing khaki pants the night before

her disappearance. When questioned, Peterson claimed that he had gone fishing for sturgeon or striped bass.

However, the police investigation revealed that he failed to bring the appropriate fishing rod and lines to catch such fish. Further revelations surfaced when it became known that Scott was having an affair with another woman. A search of Scott’s warehouse led to the recovery of a black hair on a pair of pliers resting in Scott’s boat. A mitochondrial DNA profile of the hair was consistent with Laci’s DNA. Scott Peterson was charged with murder and convicted and currently awaits his fate on death row.

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After studying this chapter you should be able to: • Review the common types of physical evidence encountered at

crime scenes

• Explain the difference between the identification and comparison of physical evidence

• Define 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

• Understand the contributions the forensic pathologist, forensic anthropologist, and forensic entomologist can make to a death investigation

physical evidence

algor mortis autopsy class characteristics comparison identification individual

characteristics livor mortis product rule rigor mortis

KEY TERMS

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It would be impossible to list all the objects that could conceivably be of importance to a crime; every crime scene obviously has to be treated on an individual basis, having its own peculiar his- tory, circumstances, and problems. It is practical, however, to list items whose scientific exami- nation is likely to yield significant 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 the uncommon and unexpected are encountered at the crime scene. Just as important, a qualified 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.

Common Types of Physical Evidence 1. Blood, semen, and saliva. All suspected blood, semen, or saliva—liquid or dried, animal or

human—present in a form to suggest a relation to the offense or the 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 serologi- cal and biochemical analysis to determine their identity and possible origin.

2. 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.

3. Drugs. Any substance seized in violation of laws regulating the sale, manufacture, distribu- tion, and use of drugs.

4. 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.

5. Fibers. Any natural or synthetic fiber whose transfer may be useful in establishing a rela- tionship between objects and/or people.

6. Fingerprints. All prints of this nature, latent and visible. 7. Firearms and ammunition. Any firearm, as well as discharged or intact ammunition, sus-

pected of being involved in a criminal offense. 8. Glass. Any glass particle or fragment that may have been transferred to a person or object

involved in a crime. Windowpanes containing holes made by a bullet or other projectile are included in this category.

9. Hair. Any animal or human hair present that could link a person with a crime. 10. 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.

11. Organs and physiological fluids. Body organs and fluids are submitted for toxicology to de- tect possible existence of drugs and poisons. This category includes blood to be analyzed for the presence of alcohol and other drugs.

12. Paint. Any paint, liquid or dried, that may have been transferred from the surface of one ob- ject 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.

13. 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, or grease and oil stains whose presence may suggest involvement in a crime.

14. Plastic bags. A disposable polyethylene bag such as a garbage bag 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.

15. Plastic, rubber, and other polymers. Remnants of these manufactured materials recovered at crime scenes may be linked to objects recovered in the possession of a suspect perpetrator.

16. Powder residues. Any item suspected of containing firearm discharge residues (see Figure 3–1). 17. Serial numbers. This category includes all stolen property submitted to the laboratory for the

restoration of erased identification numbers. 18. Soil and minerals. All items containing soil or minerals that could link a person or object to

a particular location. Common examples are soil embedded in shoes and safe insulation found on garments.

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identification The process of determining a substance’s physical or chemical identity; drug analysis, species determination, and explosive residue analysis are typical examples of this undertaking in a forensic setting

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19. Tool marks. This category includes any object suspected of containing the im- pression of another object that served as a tool in a crime. For example, a screw- driver or crowbar could produce tool marks by being impressed into or scraped along a surface of a wall.

20. Vehicle lights. Examination of vehicle headlights and taillights is normally con- ducted to determine whether a light was on or off at the time of impact.

21. 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.

The Significance of Physical Evidence The examination of physical evidence by a forensic scientist is usually undertaken for identification or comparison.

Identification Identification has as its purpose the determination of the physical or chemical iden- tity of a substance with as near absolute certainty as existing analytical techniques will permit. For example, the crime laboratory is frequently asked to identify the chemical composition of an illicit-drug preparation that may contain heroin, cocaine, barbiturates, and so on. It may be asked to identify gasoline in residues recovered from the debris of a fire, or it may have to identify the nature of explosive residues—for ex- ample, dynamite or TNT. Also, the identification of blood, semen, hair, or wood would, as a matter of routine, include a determination of species origin. For example, did an evidential bloodstain originate from a human as opposed to a dog or cat? Each of these requests requires the analysis and ultimate identification of a specific physical or chemical substance to the exclusion of all other possible substances.

The process of identification first requires the adoption of testing procedures that give characteristic results for specific 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 previ- ously obtained from a known heroin sample. Second, identification requires that the number and type of tests needed to identify a substance be sufficient to exclude all other substances. This means that the examiner must devise a specific analytical scheme that will elim- inate all but one substance from consideration. Hence, if the examiner concludes that a white pow- der contains heroin, the test results must have been comprehensive enough to have excluded all other drugs—or, for that matter, all other substances—from consideration.

Simple rules cannot be devised for defining what constitutes a thorough and foolproof ana- lytical scheme. Each type of evidence obviously requires different tests, and each test has a dif- ferent degree of specificity. Thus, one substance could conceivably be identified by one test, whereas another may require a combination of five or six different tests to arrive at an identifi- cation. In a science in which the practitioner has little or no control over the quality and quantity of the specimens received, a standard series of tests cannot encompass all possible problems and pitfalls. So the forensic scientist must determine at what point the analysis can be concluded and the criteria for positive identification satisfied; for this, he or she must rely on knowledge gained through education and experience. Ultimately, the conclusion will have to be substantiated be- yond any reasonable doubt in a court of law.

Comparison A comparison analysis subjects a suspect specimen and a standard/reference specimen to the same tests and examinations for the ultimate purpose of determining whether they have a com- mon origin. For example, the forensic scientist may place a suspect at a particular location by not- ing the similarities of a hair found at the crime scene to hairs removed from a suspect’s head (see Figure 3–2). 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. The forensic comparison is

FIGURE 3–1 The gun is fired at a set distance from the target and the gunpowder left on the target is compared to powder stains found on a victim’s clothing. The density and shape of the powder stains vary with the distance the gun was fired. Courtesy Mikael Karlsson, Arresting Images

comparison The process of ascertaining whether two or more objects have a common origin

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individual characteristics Properties of evidence that can be attributed to a common source with an extremely high degree of certainty

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FIGURE 3–2 Side-by-side comparison of hairs. Courtesy Chris Palenik, Microtrace, Elgin, Ill., www.microtracescientific.com

actually a two-step procedure. First, combinations of select properties are chosen from the sus- pect and the standard/reference specimen for comparison. The question of which and how many properties are selected obviously depends on the type of materials being examined. (This subject will receive a good deal of discussion in forthcoming chapters.) The overriding consideration must be the ultimate evidential value of the conclusion. This brings us to the second objective. Once the examination has been completed, the forensic scientist must draw a conclusion about the origins of the specimens. Do they or do they not come from the same source? 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 hence 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 come from the same source? Not necessarily so.

To comprehend the evidential value of a comparison, one must appreciate the role that prob- ability has in ascertaining the origins of two or more specimens. Simply defined, probability is the frequency of occurrence of an event. If a coin is flipped one hundred times, in theory we can expect heads to come up fifty times. Hence, the probability of the event (heads) occurring is 50 in 100. In other words, probability defines the odds at which a certain event will occur.

INDIVIDUAL CHARACTERISTICS Evidence that can be associated with a common source with an extremely high degree of probability is said to possess individual characteristics. Ex- amples of this are the ridge characteristics of fingerprints, random striation markings on bul- lets or tool marks, irregular and random wear patterns in tire or footwear impressions, handwriting characteristics, irregular edges of broken objects that can be fitted together like a jigsaw puzzle (see Figure 3–3), or sequentially made plastic bags that can be matched by striation marks running across the bags (see Figure 3–4). 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 only be concluded that this probability is so high as to defy mathematical calculations or human comprehension. Furthermore, the conclusion of common origin must be substantiated

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by the practical experience of the examiner. For example, the French scientist Victor Balt- hazard has mathematically determined that the probability of two individuals having the same fingerprints is one out of 1 � 1060, or 1 followed by sixty zeros. This probability is so small as to exclude the possibility of any two individuals having the same fingerprints. This con- tention is also supported by the experience of fingerprint examiners who, after classifying mil- lions of prints over the past hundred years, have never found any two to be exactly alike.

FIGURE 3–3 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 fit 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, ON, Canada.

FIGURE 3–4 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 a 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, New Jersey State Police.

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product rule Multiplying together the frequencies of independently occurring genetic markers to obtain an overall frequency of occurrence for a genetic profile

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Blood Factors Frequency

A 26% EsD 85% PGM 2� 2� 2%

CLASS CHARACTERISTICS One disappointment awaiting the investigator unfamiliar with the limitations of forensic science is the frequent inability of the laboratory to relate physi- cal 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 never with a single source. Here again, probability is a determining factor. For example, if we compare two one- 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 having seven similar layers of paint, not all of which were part of the car’s original color. The former will have class characteristics and could only be associated at best with one car model (which may number in the thousands), whereas the latter may be judged to have individual characteristics and to have a high probability of originating from one specific car.

Blood offers another good example of evidence that can have class characteristics. For example, suppose that two blood specimens are compared and both are found to be of human origin, type A. The frequency of occurrence in the population of type A blood is 26 percent— hardly offering a basis for establishing the common origin of the stains. However, if other blood factors are also determined and are found to compare, the probability that the two blood samples originated from a common source increases. Thus, if one uses a series of blood fac- tors that occur independently of each other, one can apply the product rule to calculate the overall frequency of occurrence of the blood in a population.

For example, in the O. J. Simpson case, a bloodstain located at the crime scene was found to contain a number of factors that compared to O. J.’s blood:

The product of all the frequencies shown in the table determines the probability that any one individual possesses such a combination of blood factors. In this instance, applying the product rule, 0.25 � 0.85 � 0.02 equals 0.0044, or 0.44 percent, or about 1 in 200 people who 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 scientist has still not individualized the bloodstains to one person—in this case, O. J. Simpson—data have been provided that will permit investigators and the courts to better assess the evidential value of the crime-scene stain. As we will learn in Chapter 11, the product rule is used to determine the frequency of occurrence of DNA profiles typically determined from blood and other biological materials. Importantly, modern DNA technology provides enough factors to allow an analyst to individualize blood, semen, and other biological materials to a single person.

Assessing the Significance of Physical Evidence One of the current weaknesses of forensic science is the inability of the examiner to assign exact or even approximate probability values to the comparison of most class physical evidence. For example, what is the probability that a nylon fiber originated from a particular sweater, or that a hair came from a particular person’s head, or that a paint chip came from a car suspected to have been involved in a hit-and-run accident? Few statistical data are available from which to derive this information, and in a society that is increasingly dependent 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 significance 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 called on to interpret the significance 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 defini- tively to a single person or object. Although investigators always try to uncover physical evidence

class characteristics Properties of evidence that can be associated only with a group and never with a single source

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with individual characteristics—such as fingerprints, tool marks, and bullets—the chances of finding class physical evidence are far greater. To deny or belittle the value of such evidence is to reject the potential role that criminalistics can play in a criminal investigation. In practice, crim- inal cases are fashioned for the courtroom around a collection of diverse elements, each pointing to the guilt or involvement of a party in a criminal act. Often, most of the evidence gathered is subjective in nature, prone to human error and bias. The believability of eyewitness accounts, confessions, and informant testimony can all be disputed, maligned, and subjected to severe at- tack and skepticism in the courtroom. Under these circumstances, errors in human judgment are often magnified to detract from the credibility of the witness.

Assessing the Value of Physical Evidence The value of class physical evidence lies in its ability to corroborate events with data in a man- ner that is, as nearly as possible, free of human error and bias. It is the thread that binds together other investigative findings that are more dependent on human judgments and, therefore, more prone to human failings. The fact that scientists have not yet learned to individualize many kinds of physical evidence means that criminal investigators should not abdicate or falter in their pur- suit of all investigative leads. However, the ability of scientists to achieve a high degree of suc- cess in evaluating class physical evidence means that criminal investigators can pursue their work with a much greater chance of success.

Admittedly, in most situations, trying to define the significance of an item of class evidence in exact mathematical terms is a difficult if not impossible goal. Although class evidence is by its nature not unique, our common experience tells us that meaningful items of physical evidence, such as those listed on pages 60–61, are extremely diverse in our environment. Select, for exam- ple, a colored fiber from an article of clothing and try to locate the exact same color on the cloth- ing of random individuals you meet, or select a car color and try to match it to other automobiles you see on local streets. Furthermore, keep in mind that a forensic comparison actually goes be- yond a mere color comparison and involves examining and comparing a variety of chemical and/or physical properties (see Figure 3–5). The point is that the chances are low of encountering two

FIGURE 3–5 Side-by-side comparison of fibers. Courtesy of Chris Palenik, Ph.D., Microtrace LLC, Elgin, IL.IS

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indistinguishable items of physical evidence at a crime scene that actually originated from differ- ent sources. Obviously, given these circumstances, only objects that exhibit a significant amount of diversity in our environment are deemed appropriate for classification as physical evidence.

In the same way, when one is dealing with more than one type of class evidence, their col- lective presence may lead to an extremely high certainty that they originated from the same source. As the number of different objects linking an individual to a crime increases, the proba- bility of involvement increases dramatically. A classic example of this situation can be found in the evidence presented at the trial of Wayne Williams (see the case reading at the end of this chapter). Wayne Williams was charged with the murders of two individuals in the Atlanta, Georgia, metropolitan area; he was also linked to the murders of ten other boys or young men. An essential element of the state’s case involved the association of Williams with the victims through a variety of fiber evidence. Twenty-eight different types of fibers 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 re- ality in the courtroom: the weight or significance accorded physical evidence is a determination left entirely to the trier of fact, usually a jury of laypeople. Given the high esteem in which scien- tists are generally held by society and the infallible image created for forensic science by books and television, it is not hard to understand why scientifically evaluated evidence often takes on an aura of special reliability and trustworthiness in the courtroom. Often physical evidence, whether individual or class, is accorded great weight during jury deliberations and becomes a primary fac- tor in reinforcing or overcoming lingering doubts about guilt or innocence. In fact, a number of jurists have already cautioned against giving carte blanche approval to admitting scientific testi- mony without first considering its relevance in a case. Given the potential weight of scientific evidence, failure to take proper safeguards may unfairly prejudice a case against the accused.

Physical evidence may also exclude or exonerate a person from suspicion. For instance, if type A blood is linked to the suspect, all individuals who have type B, AB, or O blood can be elim- inated from consideration. Because it is not possible to assess at the crime scene what value, if any, the scientist will find in the evidence collected, or what significance such findings will ulti- mately have to a jury, a thorough collection and scientific 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 indi- vidual is a difficult question to answer and is often the source of heated debate and honest dis- agreement 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 fingerprint, and how many handwriting char- acteristics tie a person to a signature? These questions defy simple answers. The task of the forensic scientist is to find as many characteristics as possible to compare one substance with another. The significance attached to the findings 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.

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. Mod- ern analytical techniques have become so sophisticated and sensitive that the criminalist must be careful to define the limits of natural variation among materials when interpreting the data gath- ered from a comparative analysis. For example, we will learn in the next chapter that two prop- erties, density and refractive index, are best suited for comparing two pieces of glass. But the latest techniques 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 magnified 1,600 times with a powerful scanning electron microscope, it is apparent that the fine details that are revealed could not be duplicated in any other paint chip. Under these circumstances, no two paint chips, even those coming from the same surface, could ever compare in the true sense of the word. Therefore, practicality dictates that such examinations be conducted at a less revealing, but more meaningful, magnification (see Figure 3–6).

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Distinguishing evidential variations from natural variations is not always an easy task. Learn- ing how to use the microscope and all the other modern instruments in a crime laboratory properly is one thing; gaining the proficiency 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.

FIGURE 3–6 (a) Two-layer paint chip magnified 244� with a scanning electron microscope. (b) The same paint chip viewed at a magnification of 1,600�.

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Latent Print File Print

FIGURE 3–7 The computerized search of a fingerprint database first requires that selected ridge characteristics be designated by a coder. The positions of these ridge characteristics serve as a basis for comparing the latent print against file fingerprints. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

Forensic Databases In a criminal investigation, the ultimate contribution a criminalist can make is to link a suspect to a crime through comparative analyses. This comparison defines the unique role of the crimi- nalist 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 finger- prints, hairs, fibers, 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 in- vestigators to uncover clues about who may have committed a crime. Today, the crime labora- tory is on the forefront of the investigation seeking to identify perpetrators. This dramatic reversal of the role of forensic science in criminal investigation has come about through the cre- ation of computerized databases that not only link all 50 states, but tie together police agencies throughout the world.

Fingerprint Databases The premier model of all forensic database systems is the Integrated Automated Fingerprint Iden- tification System (IAFIS), a national fingerprint and criminal history system maintained by the FBI. IAFIS, which first became operational in 1999, contains fingerprints and access to corre- sponding criminal history information for nearly 50 million subjects (or 500 million fingerprint images), which are submitted voluntarily to the FBI by state, local, and federal law enforcement agencies. In the United States each state has its own Automated Fingerprint Identification System (AFIS), which is linked to the FBI’s IAFIS. A crime-scene fingerprint or latent fingerprint is a dramatic find 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. The print is then electronically submitted to IAFIS and within

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minutes the search is completed against all fingerprint images in IAFIS; the examiner may re- ceive a list of potential candidates and their corresponding fingerprints for comparison and veri- fication (see Figure 3–7).

Many countries throughout the world have created national automated fingerprint identifi- cation systems that are comparable to the FBI’s model. For example, a computerized fingerprint database containing nearly nine million ten-print records connects the Home Office and 43 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 profiles, thereby linking crimes to each other and to convicted offenders. All 50 states have enacted legislation to establish a data bank containing DNA profiles of individuals con- victed of felony sexual offenses (and other crimes, depending on each state’s statute). CODIS creates investigative leads from two indexes: the forensic and offender indexes. The forensic index currently contains about 110,000 DNA profiles from unsolved crime-scene evidence. Based on a match, police in multiple jurisdictions can identify serial crimes, allowing coordi- nation of investigations and sharing of leads developed independently. The offender index contains the profiles of nearly seven million convicted or arrested individuals. The FBI has joined 15 states that collect DNA samples from those awaiting trail and will collect DNA from detained immigrants. This information will be entered into an arrestee index database. Unfor- tunately, hundreds of thousands of samples are backlogged, still awaiting DNA analysis and entry into the offender index. Law enforcement agencies search this index against DNA pro- files recovered from biological evidence found at unsolved crime scenes. This approach has proven to be tremendously successful in identifying perpetrators because most crimes in- volving 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 first national database. Currently it holds more than four million profiles, and DNA can be taken for entry into the data- base from anyone arrested for an offense likely to involve a prison term. In a typical month, matches are found linking suspects 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 firearms analysts to acquire, digitize, and compare markings made by a firearm on bullets and cartridge casings recovered from crime

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> > > > > > > > > > > > > > > > > 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, cata- loging every piece of evidence they could find. None of it led to the murderer. They had no witnesses. Sixteen years after the fact, a lone fin- gerprint, lifted from a cigarette pack found in Wallace’s house and kept for sixteen years in the

police files, was entered into the Pennsylvania State Police AFIS database. Within minutes, it hit 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 them to the man police ultimately charged with the murder of Gerald Wallace.

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scenes. The NIBIN program currently has 236 sites that are electronically joined to 16 multistate regions. The heart of NIBIN is the Integrated Ballistic Identification 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 against other images in the regional database. IBIS does not positively match bullets or casings fired from the same weapon; this must be done by a firearms examiner. IBIS does, however, facilitate the work of the firearms examiner by producing a short list of candidates for the examiner to manually compare. Nearly 900,000 pieces of crime-scene evidence have been entered in NIBIN and more than 10,000 “hits” have been recorded, many of them yielding investigative information not ob- tainable by other means.

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> > > > > > > > > > > > > > > > > Fort Collins, Colorado, and Philadelphia, Pennsylva- nia, are separated by nearly 1,800 miles, but in 2001 they were tragically linked through DNA. Troy Graves left the Philadelphia area in 1999, joined the Air Force, and settled down with his wife in Colorado. 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 profile inextricably identified him as

Philadelphia’s notorious “Center City rapist.” This as- sailant 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 he left the city. In 2002 Graves was returned to Philadelphia, where he was sentenced to life in prison without parole.

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> > > > > > > > > > > > > > > > > After a series of armed robberies in which sus- pects fired shots, the sheriff’s office 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, sher- iff’s deputies noticed suspicious activity around a local business. When they attempted to interview the suspects, the suspects fled in a vehicle. During the chase, the suspects attempted to dispose of a

handgun; deputies recovered the gun after mak- ing the arrests. The gun was test-fired and the resulting evidence entered into NIBIN, which indicated a possible link between this handgun and the four previous armed robberies. Firearms examiners confirmed the link through examination of the original evidence. The suspects were ar- rested and charged with four prior armed robbery offenses.

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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 information about make, model, year, and assembly plant on more than 13,000 vehicles with a library of more than 50,000 layers of paint. Contributors to the PDQ in- clude the RCMP and forensic laboratories in Ontario and Quebec, as well as 40 U.S. forensic laboratories and police agencies in 21 other countries. Accredited users of PDQ are required to submit 60 new automotive paint samples per year for addition to the database. The PDQ data- base 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.

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 3–8). Shoe print images can be en- tered into SICAR by either a scanner or a digital camera. This product has a comprehensive shoe sole database (Solemate™) that includes more than 17,000 footwear entries, representing over 700 shoe brands, providing investigators with a means for linking a crime-scene footwear im- pression to a particular shoe manufacturer.

1 Foster & Freeman Limited, http://www.fosterfreeman.co.uk.

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A 53-year-old man was walking his dog in the early morning hours. He was struck and killed by an un- known vehicle and later found lying in the roadway. No witnesses were present, and the police had no leads regarding the suspect vehicle. A gold metal- lic 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 gold metallic paint particles were recov- ered. Most of these particles contained only top- coats, whereas one minute particle contained two primer layers and a limited amount of colorcoat. The color of the primer surface layer was similar to that typically associated with some Fords. Subse- quent spectral searches in the Paint Data Query (PDQ) database indicated that the paint most likely originated from a 1990 or newer Ford.

The most discriminating aspect of this paint was the unusual-looking gold metallic topcoat color. A search of automotive repaint books yielded only one color that closely matched the paint recovered

in the 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 in- vestigating 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 af- ter the make, model, and year information was re- layed 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 compar- isons showed that the painted plastic piece recov- ered from the scene could be physically fitted together with the molding, and 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

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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

rigor mortis A medical condition that occurs after death and results in the stiffening of muscle mass. The rigidity of the body gradually disappears 24 hours after death and disappears within 36 hours

autopsy The medical dissection and examination of a body in order to determine the cause of death

forensic pathologist An individual who investigates sudden, unnatural, unexplained, or violent deaths.

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FIGURE 3–8 The crime-scene footwear print on the right is being searched against eight thousand sole patterns to determine its make and model. Courtesy Foster & Freeman Limited, Worcestershire, U.K., www.fosterfreeman.co.uk

The Murder Scene: Death Investigation Unfortunately, the most important piece of evidence at many crime scenes is the dead body of a victim. When foul play is suspected, a victim’s corpse is subjected to the same kind of intense physical analysis as any other piece of evidence. This task falls primarily to a forensic pathologist, often aided by the skills of specialists including forensic anthropologists and forensic entomolo- gists. In its broadest sense, forensic pathology involves the study of medicine as it relates to the ap- plication of the law, particularly criminal law. In practice, this most often involves the investigation of sudden, unnatural, unexplained, or violent deaths.

Role of the Forensic Pathologist Forensic pathology involves the investigation of sudden, unnatural, unexplained, or violent deaths. Typically, forensic pathologists, in their role as medical examiners or coroners, must an- swer several basic questions: Who is the victim? What injuries are present? When did the injuries occur? Why and how were the injuries produced? The primary role of the medical examiner is to determine the cause of death. If a cause cannot be found through observation, an autopsy is nor- mally performed to establish the cause of death. The manner in which death occurred is classi- fied into five categories: natural, homicide, suicide, accident, or undetermined, based on the circumstances surrounding the incident.

ESTIMATING TIME OF DEATH After a human body expires, it goes through several stages of de- composition. A medical examiner participating in a criminal investigation can often estimate the time of death by evaluating the stage of decomposition in which the victim was found. Immedi- ately following death, the muscles relax and then become rigid. This condition, rigor mortis, manifests itself within the first 24 hours and disappears within 36 hours. Another condition oc- curring in the early stages of decomposition is livor mortis. When the human heart stops pump- ing, the blood begins to settle in the parts of the body closest to the ground. The skin will appear dark blue or purple in these areas. The onset of this condition begins immediately and continues for up to 12 hours after death. The skin will not appear discolored in areas where the body is

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algor mortis Postmortem changes that cause a body to lose heat

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restricted by either clothing or an object pressing against the body. This information can be use- ful in determining whether the victim’s position was changed after death occurred.

Other physical and chemical changes within the body are also helpful in approximating the time of death. Algor mortis is the process by which the body temperature continually cools after death until it reaches the ambient or room temperature. The rate of heat loss is influenced by fac- tors such as the location and size of the body, the victim’s clothing, and weather conditions. Be- cause of such factors, this method can only estimate the approximate time period since death. As a general rule, beginning about an hour after death, the body will lose heat at a rate of approxi- mately 1–1.5°F per hour until the body reaches the environmental temperature.

Another approach helpful for estimating the time of death is determining potassium levels in the ocular fluid (vitreous humor). After death, cells within the inner surface of the eyeball release potassium into the ocular fluid. 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. During the autopsy, other factors may indicate the time period in which death occurred. For example, the amount of food in the stomach can help estimate when a per- son’s last meal was eaten. This information can be valuable when investigating a death.

Frequently, medical examiners must perform autopsies if a death is deemed suspicious or un- explained. The cause of death may not always be what it seems at first glance. For example, a decedent with a gunshot wound and a gun in his hand may appear to have committed suicide. However, an autopsy may reveal that the victim actually died of suffocation and the gunshot wound occurred after death to cover up the commission of a crime.

Role of the Forensic Anthropologist Forensic anthropology is concerned primarily with the identification and examination of human skeletal remains. Skeletal bones are remarkably durable and undergo an extremely slow break- down process that lasts decades or centuries. Because of their resistance to rapid decomposition, skeletal remains can provide a multitude of individual characteristics. An examination of bones may reveal their sex, approximate age, race, and skeletal injury.

RECOVERING AND PROCESSING REMAINS Thorough documentation is required throughout the processes of recovery and examination of human remains. The sites where human remains are found must be treated as a crime scene (see Figure 3–9). These sites are usually located by

FIGURE 3–9 Crime-scene site showing a pelvis partly buried in sand and a femur lying across a revolver. Courtesy Paul Sledzik, National Transportation Safety Board

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FIGURE 3–10 (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. (a) Geoff Brightling/ESPL-modelmaker © ESPL/Dorling Kindersley; (b) Giuliano Fornari © Dorling Kindersley

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 lo- cate all bones if they are scattered or other aspects of evidence such as footwear impressions or discarded items. Some tools can be useful in the search for evidence at a “tomb” site, including aerial photography, metal detectors, ground-penetrating radar, infrared photography, apparatuses that detect the gases produced by biological decomposition, and so-called cadaver dogs that de- tect the odors caused by biological decomposition. All items that are found must be tagged, pho- tographed, 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 Po- sitioning System [GPS] coordinates) and the spatial relationship of all evidence. Once the skele- tal remains have been recovered, they can be examined to deduce information about the identity of the decedent.

DETERMINING VICTIM CHARACTERISTICS 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. Female pelvic bones tend to show a wider, more circular opening than that of a male pelvis be- cause of a woman’s childbearing capabilities. The female sacrum (flat bone above the tailbone) is wider and shorter (see Figure 3–10 [a]); the length and width of the male sacrum are roughly equal (see Figure 3–11 [b]). In general, male craniums are larger in overall size than those of fe- males. 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 3–10).

FIGURE 3–11 Male (left) and female (right) human skulls showing male skull’s larger size and more pronounced brow bone. Courtesy Corbis RF

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FIGURE 3–12 A lateral view of a fetal skull showing the separated bones of the skull before they have had a chance to fuse. Courtesy Ralph T. Hutchings

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 the length of the long bones (femur and humerus) when compared to a known growth curve. Different sections of the skull also fuse to- gether at different stages during early development, and the appearance of fused or divided sec- tions can be used to estimate age of bones still in early developmental stages (see Figure 3–12). 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 (lower jaw), fingers, wrist, long bones, and clavicle (see Figure 3–13). The average age at which each of these 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 identified by the smaller size and the presence of developing teeth (see Figure 3–14). After age 21, age is estimated by the level of change experienced by the surfaces of the bones, especially in area of common wear such as the pubic symphysis. The pubic symphyseal face shown in Figure 3–15 is a raised platform that slowly changes over the years from a rough, rugged surface to a smooth, well-defined area.

Although the categorization of “race” has come under scrutiny and is hard to define, forensic anthropologists use broad classes to characterize the likely (but not definite) 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 (Asian descent), oval in Caucasoid skeletons (European descent), and square in Negroid skeletons (African descent). The nasal cavity tends to be small and rounded in Mongoloids, long

FIGURE 3–13 Colored X-rays of healthy human hands at 3 years (left) and 20 years. Bones are red with blue flesh. The child’s hand has areas of cartilage in the joints between the finger bones (epiphyseal areas), where bone growth and fusion will occur. In the adult hand, all the bones are present and the joints have closed. Courtesy SPL, Photo Researchers, Inc.

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FIGURE 3–14 The skull of a young child, with part of the jaw cut away to show the developing teeth. Courtesy Ralph T. Hutchings

FIGURE 3–15 The pubic symphysis shown magnified beneath human pelvic bones. Courtesy Pearson Education Custom Publishing

and narrow in Caucasoids, and wide in Negroids. Skeletal remains of Asian ancestry, including those of Native American descent, also tend to have “scooped-out” or shovel-shaped incisor teeth.

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.

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OTHER CONTRIBUTIONS OF FORENSIC ANTHROPOLOGY A forensic anthropologist may also create facial reconstructions to help identify skeletal remains. Facial reconstruction uses the victim’s actual cranium and takes into account the estimated age, ancestry, and gender (see Figure 3–16). 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 anthropologists can help identify victims through the collection of bone fragments. Definite identification of remains can be made only by analyzing the decedent’s DNA profile, fingerprints, or medical records. Recovered remains may still contain some soft tissue material, which may yield a DNA profile for identification purposes. Sometimes the tissue of the hand is still present, though dried out. It may be possible to rehydrate the tissue to recover fingerprints. However, usually the identification of the remains will depend on medical records, especially dental records of the individual.

Role of the Forensic Entomologist The study of insects and their relation to a criminal investigation is known as forensic entomol- ogy. Such a practice is commonly used to estimate the time of death when the circumstances sur- rounding the crime are unknown. This determination can be carried out by studying the stage of development of maggots or insect sequence of arrival.

DETERMINING TIME OF DEATH After decomposition begins, necrophilious insects, or insects that feed on dead tissue, are the first to infest the body, usually within 24 hours. The most com- mon and important of these is the blowfly, recognized by its green or blue color. Blowfly eggs are laid in the human remains and ultimately hatch into maggots, or fly larvae, which consume human organs and tissues (see Figure 3–17). Typically, a single blowfly can lay thousands of eggs dur- ing its lifetime (see Figure 3–18). The resulting larvae gather and feed as a “maggot mass” on the decomposing remains. Forensic entomologists can approximate how long a body has been left exposed by examining the stage of development of the fly larvae. This kind of determination is

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y Identifying a Serial Killer’s Victims The worst serial killer in America 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 identifi- cation was 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 make individual identifications for most of the victims. Clyde Snow, the world-renowned forensic anthropol- ogist from Oklahoma, was asked to help the investigators make these difficult identifications.

Snow began by making a 35-point examination of each skull for comparison to known individuals. By examining each skeleton, he made sure each bone was correctly attrib- uted 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 when attempting to match the victims with the descriptions of missing people.

After narrowing the possibilities to missing people fitting the general description, investigators consulted potential vic- tims’ hospital and dental records. Evidence of injury, illness, surgery, or other unique skeletal defects was used to make iden- tifications. Snow also pointed out features that gave clues to the victim’s behavior and medical history. For example, he discov- ered that one of Gacy’s victims had an old fracture of 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 identified.

For the most difficult cases, Snow called in the help of forensic sculptor and facial reconstructionist Betty Pat Gatliff. She used clay and depth markers to put the flesh back on the faces of these forgotten boys in the hopes that someone would recognize them after their photographs were released to the me- dia. Her efforts were successful, but investigators found some families unwilling to accept the idea that their loved ones were among Gacy’s victims. Even with Gatliff’s help, nine of Gacy’s victims remain unidentified.

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best for a timeline of hours to approximately 1 month, because the blowfly goes through the stages of its life cycle at known time intervals and in an identifiable sequence. By determining the most developed stage of fly found on the body, entomologists can approximate the post- mortem interval (PMI), or the time that has elapsed since death (see Figure 3–19). Newly emerged flies are of important forensic interest, as they indicate that an entire blowfly cycle has

FIGURE 3–16 Trooper Sarah Foster, a Michigan State Police forensic artist, works on a three- dimensional facial reconstruction from an unidentified human skull at the Richmond post in Richmond, Michigan. Courtesy Paul Sancya, AP Wide World Photos

FIGURE 3–17 A scanning electron micrograph of 2-hour- old blowfly maggots. Courtesy Dr. Jeremy Burgess, Photo Researchers, Inc.

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been completed on the decomposing body. Likewise, empty pupal cases indicate that a fly has completed its entire life cycle on the body.

These determinations are not always straightforward, however. The time required for stage development is affected by environmental influences such as geographical location, climate, weather conditions, and the presence of drugs. For example, cold temperatures hinder the devel- opment of fly eggs into adult flies. The forensic entomologist must consider these conditions when estimating the PMI.

FIGURE 3–18 A blowfly depositing a mass of eggs. Courtesy Volker Steger, Photo Researchers, Inc.

Eclosion: Adult Fly Emerges

Larva Stage III

Postfeeding

Puparium

Early

Late

Oviposition

Egg

Eclosion: Maggot Emerges

Larva Stage I

Larva Stage II

FIGURE 3–19 Typical blowfly life cycle from egg deposition to adult fly emergence. This cycle is representative of any one of the nearly ninety species of blowflies in North America. Courtesy E. P. Catts, Ph.D., deceased, and Neal H. Haskell, Ph.D., forensic entomology consultant, www.forensic-entomology.com

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Information about the arrival of other species of insects may also aid in determining the PMI. The sequence of arrival of these groups is dependent primarily on the body’s natural decomposition process. Predator insects generally arrive to prey on the necrophagous insects. Several kinds of beetles may be found, either feeding directly on the corpse tissues or as pred- ators feeding on blowfly 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 surrounding veg- etation. Ants and wasps are an example of omnivore insects. Finally, indigenous insects, such as spiders, arrive; their presence on or near the body is coincidental as they move about their environment.

The known sequence of arrival of different insect groups can help determine the PMI. This method is usually used when months have elapsed between the time when the decedent died and when the body was found. In order to make an accurate estimate, the forensic ento- mologist must compare the species found on the body to experimental data from that geo- graphical area. The entomologist then looks first for what earlier groups are missing. This sets a minimum PMI. For example, if experiments in that area have shown that all necrophil- ious insects leave the body after about 3 months and no necrophilious insects are found on the body, it can be deduced that the decedent has been deceased for at least 3 months. If a particular entomologist is very familiar with the insect patterns of an area, he or she may be able to further define the PMI range by looking for what groups have not yet arrived. This method may also be useful to determine season of death. However, it is important to re- member that the diversity of insects found on a body is also affected by the body’s location, weather and temperature conditions, habitat characteristics, indigenous species, and charac- teristics of the body.

OTHER CONTRIBUTIONS OF FORENSIC ENTOMOLOGY Entomological evidence can also pro- vide other pertinent information. In general, insects first colonize the body’s natural moist orifices. However, if open wounds are present, they prefer to colonize there first. Because decomposition processes may conceal wounds, colonization away from natural orifices may help locate wounds on the body. If maggots are found extensively on the hands and forearms, for example, this suggests the

> > > > > > > > > > > > > > > > > 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, searchers 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 Westerfield, was ac- cused of kidnapping Danielle, killing her, and dumping her body in the desert. During the subsequent investigation, Danielle’s blood was found on Westerfield’s clothes, her fin- gerprints and blood were found in his RV, and child pornogra- phy was found on his home computer.

The actual time of the 7-year-old’s death became a central issue during the murder trial. Westerfield had been under con- stant 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. Conflicting expert testimony was elicited from forensic entomologists who were called upon to estimate when the body was dumped. The forensic entomolo- gist who went to the dump site, witnessed the autopsy, and col- lected and analyzed insects from both locations estimated that Danielle died between February 16 and 18. A forensic ento- mologist 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 mummified Danielle’s body almost immediately, thus causing a delay in the flies col- onizing the body.

The jurors convicted Westerfield of the kidnapping and murder of Danielle Van Dam, and a San Diego judge sentenced David Westerfield to death. Danielle Van Dam’s parents filed and settled a wrongful death suit against Westerfield requiring his automotive and homeowners’ insurance carriers to pay the Van Dams an undisclosed amount, reported to be between $400,000 and $1 million.

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presence of defensive wounds on the victim. Insects that have fed on the body may also have accu- mulated any drugs present in the flesh, and these insects can yield the identity of these drugs.

If resources allow, all insect evidence should be carefully collected by a forensic entomol- ogy 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 photographed and documented before collection. Specimen samples should be taken from each area on the body where they are found and labeled to show where they were collected from.

Physical evidence is usually examined by a forensic scientist for identification or comparison purposes. The object of iden- tification is to determine the physical or chemical identity with as near absolute certainty as existing analytical techniques will permit. Identification first requires the adoption of testing pro- cedures that give characteristic results for specific standard materials. Once this is done, the examiner uses an appropriate number of tests to identify a substance and exclude all other substances from consideration. The identification process is normally used in crime laboratories to identify drugs, explo- sives, and petroleum products. Also, evidence such as blood, semen, or hair is routinely identified in a crime laboratory. Normally, these identifications would include a determination for species origin (such as human blood or rabbit hair).

A comparative analysis has the important role of deter- mining whether a suspect specimen and a standard/refer- ence specimen have a common origin. Both the standard/ reference specimen and the suspect specimen are subject to the same tests. Evidence that can be associated with a com- mon source with an extremely high degree of probability is said to possess individual characteristics. Evidence associ- ated only with a group is said to have class characteristics. Nevertheless, the high diversity of class evidence in our en- vironment makes their comparison significant in the context of a criminal investigation. As the number of different ob- jects linking an individual to a crime scene increases, so does the likelihood of that individual’s involvement with the crime. Importantly, 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.

A dramatic enhancement of the role of forensic science in criminal investigation has come about through the creation of computerized databases. The Integrated Automated Finger- print Identification System (IAFIS), a national fingerprint and

criminal history system, is maintained by the FBI. The FBI’s Combined DNA Index System (CODIS) enables federal, state, and local crime laboratories to electronically exchange and compare DNA profiles, thereby linking crimes to each other and to convicted offenders. The National Integrated Ballistics Information Network (NIBIN), maintained by the Bureau of Alcohol, Tobacco, Firearms and Explosives, allows firearms analysts to acquire, digitize, and compare markings made by a firearm on bullets and cartridge casings recovered from crime scenes. The International Forensic Automotive Paint Data Query (PDQ) database contains chemical and color information pertaining to original automotive paints. SICAR (shoeprint image capture and retrieval) has a comprehensive shoe sole database.

Physical evidence left behind at a crime scene, properly handled and preserved, plays a crucial role in reconstructing the events that took place surrounding the crime. Crime-scene reconstruction relies on the combined efforts of medical ex- aminers, criminalists, and law enforcement personnel to re- cover physical evidence and to sort out the events surrounding the occurrence of a crime.

Several special forensic science services are available to the law enforcement community to augment the services of the crime laboratory in a death investigation. The services of a forensic pathologist, forensic anthropologist, and forensic entomologist may be required in the investigation of a sudden, unnatural, unexplained, or violent death. Forensic pathologists examine the body of a decedent to estimate cause of death and time since death or postmortem interval (PMI). Forensic anthropologists seek to identify human re- mains by examining characteristics of skeletal remains and creating an estimated profile of the victim. Forensic ento- mologists examine the insect evidence from a crime scene or associated with a body. They can then use this information to estimate PMI.

< < < < < < < < < < < chapter summary

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review questions

1. The process of ___________ determines a substance’s physical or chemical identity with as near absolute cer- tainty as existing analytical techniques will permit.

2. The number and type of tests needed to identify a sub- stance must be sufficient to ___________ all other sub- stances from consideration.

3. A(n) ___________ analysis subjects a suspect specimen and a standard/reference specimen to the same tests and examination in order to determine 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 and not with a single source is said to possess ___________ characteristics.

7. True or False: One of the major deficiencies of forensic science is the inability of the examiner to assign exact or approximate probability values to the comparison of most class physical evidence. ___________

8. 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.

9. The ___________ accorded physical evidence during a trial is left entirely to the trier of fact.

10. True or False: Physical evidence cannot be used to ex- clude or exonerate a person from suspicion of commit- ting a crime. ___________

11. True or False: The distinction between individual and class evidence is always easy to make. ___________

12. Modern analytical techniques have become so sensitive that the forensic examiner must be aware of the ___________ among materials when interpreting the significance of comparative data.

13. True or False: A fingerprint can be positively identified through the IAFIS database. ___________

14. A database applicable to DNA profiling is ___________.

15. When ___________ sets in after death, the skin appears dark blue or purple in the areas closest to the ground.

16. True or False: One method for approximating the time of death is to determine body temperature. ___________

17. ___________ involves the study of medicine as it re- lates to the application of the law, most often pertain- ing to the investigation of sudden, unnatural, unexplained, or violent deaths.

18. The cause of death, whether natural, homicide, suicide, accident, or undetermined, is normally determined by performing a(n) ___________ and investigating the cir- cumstances surrounding the death.

19. In determining time of death, ___________ occurs after death and results in the stiffening of body parts in the position they are in when death occurs, ___________ oc- curs after death and results in the settling of blood in areas of the body closest to the ground, and ___________ refers to postmortem changes that cause a body to lose heat.

20. Another approach for estimating the time of death is to determine potassium levels in the ___________ fluid.

21. The field of ___________ takes advantage of the durable nature of bones over long periods of time to examine and identify human skeletal remains through a multitude of individual characteristics.

22. Female bone structure differs from male bone structure within the ___________ area because of a woman’s childbearing capabilities.

23. A forensic anthropologist may also help create a(n) ___________ of the decedent from which a composite drawing of the victim can be drawn and advertised in an attempt to identify the victim.

24. True or False: Definite identification of remains cannot be made through the analysis of the decedent’s DNA profile, fingerprints, or medical records. ___________

25. True or False: Sites where human remains are found must be treated as a crime scene, and the site and sur- rounding area should be secured, searched, and care- fully processed. ___________

26. Once all bones and other evidence are found at a “tomb” site, a(n) ___________ should be made to show the exact location of each item.

27. The study of insects and their relation to a criminal in- vestigation, known as ___________, is commonly used to estimate the time of death when the circumstances surrounding the crime are unknown.

28. By determining the oldest stage of fly found on the body and taking environmental factors into consideration, en- tomologists can approximate the ___________ interval.

29. Entomological evidence collected at a scene should in- clude samples from every area where insects are found and ___________ measurements.

30. True or False: Another method to determine PMI is by observing the schedule of arrival of different insect species on the body. ___________ ISB

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application and critical thinking

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 characteristics that may be found in an individual’s ge- netic profile. Using the product rule, rank each of these combinations of DNA characteristics from most common to least common. The number after each characteristic in- dicates 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 indi- vidual characteristics and explain your answers.

a. An impression from a new automobile tire

b. A fingerprint

c. A spent bullet cartridge

d. A mass-produced synthetic fiber

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 contain information that relates primarily to evidence ex- hibiting class characteristics? Which ones contain infor- mation that relates primarily to evidence exhibiting individual characteristics? Explain your answers.

5. Which of the discussed conditions examined during au- topsy could help the forensic pathologist determine time since death if the victim expired within 1 or 2 hours of being discovered? Which would be of little or no assis- tance in this determination?

6. A highly weathered skeleton is recovered from a remote wooded site. Only the upper torso and cranium were re- covered. The clavicle is found to be unfused and the cra- nium features a very prominent brow bone and sharp, protruding mastoid process. What can be surmised about the victim’s identity from this information?

Houck, M. M., “Statistics and Trace Evidence: The Tyranny of Numbers,” Forensic Science Communications, 1, no. 3 (1999) www.fbi.gov/hq/lab/fsc/backissu/oct1999/ houck.htm

Houck, M. M., and J. A. Siegel, Fundamentals of Forensic Science. Burlington, MA: Elsevier Academic Press, 2006.

further references

Osterburg, James W., “The Evaluation of Physical Evidence in Criminalistics: Subjective or Objective Process?” Journal of Criminal Law, Criminology and Police Science 60 (1969): 97.

Thornton, John I., Paul L. Kirk’s Crime Investigation, 2nd ed. New York: Wiley, 1974.

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In 1982, the state of Georgia convicted Wayne Williams of murdering several boys and young men in the Atlanta area. The case featured unique uses of fiber evidence that proved crucial to establishing Williams’s guilt. The case also high- lighted the effectiveness of statistical probability for estab- lishing links between evidence found at multiple crime scenes.

1. In what respects did the use of fiber evidence in the Williams case differ significantly from its use in previ- ous cases?

2. What did investigators hope to learn from their initial ex- amination of fibers found on the bodies of several mur- der victims found in the Atlanta area from July 1979 to May 1981? What steps did they take to gather this infor- mation? What did they learn from their investigations? What was the significance of this information?

case analysis

3. How could information on the source of the fibers be helpful to investigators? Explain how investigators may use information about the source of a fiber to help them locate the perpetrator.

4. What pieces of information did investigators collect from the West Point Pepperell Corporation that led them to conclude that the fibers found on Nathaniel Cater’s body came from the carpeting in Wayne Williams’s house? Explain the importance of each of these pieces of information for connecting Williams to Cater’s murder.

5. Describe how investigators used the concepts of statisti- cal probability to tie Williams to Nathaniel Cater as well as to his other victims.

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On February 26, 1982, a Fulton County, Ga., Superior Court jury returned a verdict of “guilty as charged” on two counts of murder brought against Wayne Bertram Williams by a Fulton County grand jury in July 1981. Williams had been on trial since December 28, 1981, for the asphyxial murders of Nathaniel Cater and Jimmy Payne in April and May of 1981. During the 8-week trial, evidence linking Williams to those mur- ders and to the murders of 10 other boys or young men was introduced.

An essential part of this case, presented by the Fulton County District Attorney’s Office, involved the association of fibrous debris removed from the bodies of 12 murder victims with objects from the everyday environment of Williams.

Fiber evidence has often been an important part of criminal cases, but the Williams trial differed from other cases in several respects. Fiber evidence has not played a significant role in any case in- volving a large number of murder victims. The victims whose deaths were charged to Williams were 2 of 30 black children and black young men who were reported missing or who had died under suspi- cious circumstances in the Atlanta area over a 22-month period beginning in July 1979. During the trial, fiber evidence was used to associate Williams with 12 of those victims.

Fiber evidence is often used to corroborate other evidence in a case—it is used to support other testimony presented at a trial. This was not the situation in the Williams trial. Other evidence and other aspects of the trial were important but were used to support and complement the fiber evidence, not the usual order of things. The “hair and fiber matches” between Williams’s environment and 11 of the 12 murder victims discussed at the trial were so significant that, in the author’s opinion, these victims were positively linked to both the residence and automobiles that were a major part of the world of Wayne Williams.

Another difference between this case and most other cases was the extremely large amount of pub- licity surrounding both the investigation of the missing and murdered children and the arrest and sub- sequent trial of Williams. Few other murder trials have received the attention that the Williams case received. . . .

It is often difficult to get an accurate picture from press reports of the physical evidence introduced at a trial and the significance of that evidence. This article will also set forth in some detail the fiber evidence that linked Williams to the murder victims.

By discussing only the fiber evidence introduced at the trial, many other aspects of the case against Williams are being neglected. Additional evidence dealing with Williams’s motivations—his character and behavior, his association with several of the victims by eyewitness ac- counts, and his link to a victim recovered from a river in Atlanta—[were] also essential to the case. . . .

Development of Williams as a Murder Suspect Before Wayne Williams became a suspect in the Nathaniel Cater murder case, the Georgia State Crime Laboratory located a number of yellowish-green nylon fibers and some violet acetate fibers on the bodies and clothing of the murder victims whose bodies had been recovered during the period of July 1979 to May 1981. The names of those victims were included on the list of missing and murdered children that was compiled by the Atlanta Task Force (a large group of investigators from law enforcement agencies in the Atlanta area). The yellowish-green nylon fibers were generally similar to each other in appearance and properties and were considered to have originated from a single source. This was also true of the violet acetate fibers. Although there were many other similarities that would link these

Case Study

Fiber Evidence and the Wayne Williams Trial

Reprinted in part from FBI Law Enforcement Bulletin, March and May 1984.

Harold A. Deadman Special Agent, Microscopic Analysis Unit, Laboratory Division Federal Bureau of Investigation, Washington, D.C.

Wayne Williams is shown talking to police outside his home. Courtesy CORBIS-NY

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that this was a relatively rare fiber type, and therefore, would not be present in large amounts (or in a large number of carpets).

[Williams’s] Carpet Shortly after Williams was developed as a suspect, it was deter- mined the yellowish-green nylon fibers were manufactured by the Wellman Corporation. The next step was to ascertain, if possible, how much carpet like Williams’s bedroom carpet had been sold in the Atlanta area—carpet composed of the Wellman fiber and dyed with the same dye formulation as [Williams’s] carpet. Names of Wellman Corporation customers who had purchased this fiber type, technical information about the fiber, and data concerning when and how much of this fiber type had been manufactured were obtained.

It was confirmed that the Wellman Corporation had, in fact, manufactured the fiber in Williams’s carpet and that no other fiber manufacturer was known to have made a fiber with a similar cross section. It was also determined that fibers having this cross- sectional shape were manufactured and sold during the years 1967 through 1974. Prior to 1967, this company manufactured only a round cross section; after 1974, the unusual trilobal cross section seen in Williams’s carpet was modified to a more regular trilobal cross-sectional shape. A list of sales of that fiber type during the period 1967 through 1974 was compiled. . . .

Through numerous contacts with yarn spinners and carpet manufacturers, it was determined that the West Point Pepperell Corporation of Dalton, Ga., had manufactured a line of carpet called “Luxaire,” which was constructed in the same manner as [Williams’s] carpet. One of the colors offered in the “Luxaire” line was called “English Olive,” and this color was the same as that of [Williams’s] carpet (both visually and by the use of dis- criminating chemical and instrumental tests).

It was learned that the West Point Pepperell Corporation had manufactured the “Luxaire” line for a five-year period from December 1970 through 1975; however, it had only purchased Wellman 181B fiber for this line during 1970 and 1971. In De- cember 1971, the West Point Pepperell Corporation changed the fiber composition of the “Luxaire” line to a different nylon fiber, one that was dissimilar to the Wellman 181B fiber in appearance. Accordingly, “Luxaire” carpet, like [Williams’s] carpet, was only manufactured for a 1-year period. This change of carpet fiber af- ter only 1 year in production was yet another factor that made [Williams’s] carpet unusual.

It is interesting to speculate on the course the investigation would have taken if the James Jackson Parkway Bridge had not been covered by the surveillance team. The identification of the manufacturer of the nylon fibers showing up on the bodies could still have occurred and the same list of purchasers of the Wellman fiber could have been obtained. The same contacts with the yarn and carpet manufacturers could have been made; however, there would not have been an actual carpet sample to display. It is be- lieved that eventually the carpet manufacturer could have been determined. With a sample of carpet supplied by West Point Pepperell—which they had retained in their files for over 10 years— it would have been possible to conduct a house-by-house search of the Atlanta area in an attempt to find a similar carpet. Whether this very difficult task would have been attempted, of course, will never be known. A search of that type, however, would have

murders together, the fiber linkage was notable since the possi- bility existed that a source of these fibers might be located in the future.

Initially, the major concern with these yellowish-green nylon fibers was determining what type of object could have been their source. This information could provide avenues of investigative activity. The fibers were very coarse and had a lobed cross- sectional appearance, tending to indicate that they originated from a carpet or a rug. The lobed cross-sectional shape of these fibers, however, was unique, and initially, the manufacturer of these fibers could not be determined. Photomicrographs of the fibers were prepared for display to contacts within the textile industry. On one occasion, these photomicrographs were distrib- uted among several chemists attending a meeting at the research facilities of a large fiber producer. The chemists concurred that the yellowish-green nylon fiber was very unusual in cross-sectional shape and was consistent with being a carpet fiber, but again, the manufacturer of this fiber could not be determined. Contacts with other textile producers and textile chemists likewise did not result in an identification of the manufacturer.

In February 1981, an Atlanta newspaper article publicized that several different fiber types had been found on two murder victims. Following the publication of this article, bodies recov- ered from rivers in the Atlanta metropolitan area were either nude or clothed only in undershorts. It appeared possible that the vic- tims were being disposed of in this undressed state and in rivers in order to eliminate fibers from being found on their bodies.1

On May 22, 1981, a four-man surveillance team of personnel from the Atlanta Police Department and the Atlanta Office of the FBI was situated under and at both ends of the James Jackson Parkway Bridge over the Chattahoochee River in northwest Atlanta. Around 2 A.M., a loud splash alerted the surveillance team to the presence of an automobile being driven slowly off the bridge. The driver was stopped and identified as Wayne Bertram Williams.

Two days after Williams’s presence on the bridge, the nude body of Nathaniel Cater was pulled from the Chattahoochee River, approximately 1 mile downstream from the James Jackson Parkway Bridge. A yellowish-green nylon carpet-type fiber, simi- lar to the nylon fibers discussed above, was recovered from the head hair of Nathaniel Cater. When details of Williams’s reason for being on the bridge at 2 A.M. could not be confirmed, search war- rants for Williams’s home and automobile were obtained and were served on the afternoon of June 3, 1981. During the late evening hours of the same day, the initial associations of fibers from Cater and other murder victims were made with a green carpet in the home of Williams. Associations with a bedspread from Williams’s bed and with [Williams’s] family dog were also made at that time.

An apparent source of the yellowish-green nylon fibers had been found. It now became important to completely characterize these fibers in order to verify the associations and determine the strength of the associations resulting from the fiber matches. Be- cause of the unusual cross-sectional appearance of the nylon fiber and the difficulty in determining the manufacturer, it was believed

1Prior to the publication of the February 11, 1981, newspaper article, one victim from the task force list, who was fully clothed, had been recovered from a river in the Atlanta area. In the 21⁄2-month period after publication, the nude or nearly nude bodies of 7 of the 9 victims added to the task force list were recovered from rivers in the Atlanta area.

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4. Information from the Atlanta Regional Commission showed that there were 638,995 occupied housing units in the Atlanta metropolitan area in November 1981.4 Using this figure, the chance of randomly selecting an occupied housing unit in met- ropolitan Atlanta and finding a house with a room having car- pet like Williams’s carpet was determined to be 1 chance in 7,792—a very low chance.

To the degree that the assumptions used in calculating the above probability number are reasonable, we can be confident in arriv- ing at a valid probability number. . . .

The probability figures illustrate clearly that [Williams’s] carpet is, in fact, very uncommon. To enhance the figures even further, it is important to emphasize that these figures are based on the assumption that none of the carpet of concern had been discarded during the past 11 years. In fact, carpet of this type, often used in commercial settings, such as apartment houses, would probably have had a normal life span of only 4 or 5 years. . . .5

The Williams Trial To any experienced forensic fiber examiner, the fiber evidence linking Williams to the murder victims was overwhelming. But regardless of the apparent validity of the fiber findings, it was dur- ing the trial that its true weight would be determined. Unless it could be conveyed meaningfully to a jury, its effect would be lost. Because of this, considerable time was spent determining what should be done to convey the full significance of the fiber evi- dence. Juries are not usually composed of individuals with a sci- entific background, and therefore, it was necessary to “educate” the jury in what procedures were followed and the significance of the fiber results. In the Williams case, over 40 charts with over 350 photographs were prepared to illustrate exactly what the crime laboratory examiners had observed. . . .

Representatives of the textile fiber industry, including techni- cal representatives from the Wellman and West Point Pepperell Corporations, were involved in educating the jury regarding tex- tile fibers in general and helped lay the foundation for the con- clusions of the forensic fiber examiners. The jury also was told about fiber analysis in the crime laboratory.

The trial, as it developed, can be divided into two parts. Ini- tially, testimony was given concerning the murders of Nathaniel Cater and Jimmy Ray Payne, the two victims included in the in- dictment drawn against Williams in July 1981. Testimony was then given concerning Williams’s association with 10 other mur- der victims.

The fiber matches made between fibers in Williams’s envi- ronment and fibers from victims Payne and Cater were discussed. The items from Williams’s environment that were linked to either

accurately answered an important question that was discussed at the trial—the question of how many other homes in the Atlanta area had a carpet like [Williams’s] carpet. An estimation, to be discussed later, based on sales records provided by the West Point Pepperell Corporation indicated that there was a very low chance (1/7,792) of finding a carpet like Williams’s carpet by randomly selecting occupied residences in the Atlanta area.

Only the West Point Pepperell Corporation was found to have manufactured a carpet exactly like [Williams’s] carpet. Even though several manufacturers had gone out of business and could not be located, it was believed that, considering the many vari- ables that exist in the manufacture of carpet and the probable uniqueness of each carpet manufacturer’s dye formulations, it would be extremely unlikely for two unrelated companies to con- struct a carpet or dye the carpet fibers in exactly the same way. A large number of other green fibers, visually similar in color to Williams’s carpet, were examined. None was found to be consistent with fibers from [Williams’s] carpet.

Probability Determinations To convey the unusual nature of [Williams’s] residential carpet, an attempt was made to develop a numerical probability— something never before done in connection with textile materials used as evidence in a criminal trial.2 The following information was gathered from the West Point Pepperell Corporation:

1. West Point Pepperell reported purchases of Wellman 181B fiber for the “Luxaire” line during a 1-year period. The Well- man 181B fiber was used to manufacture “Luxaire” carpet from December 1970 until December 1971, at which time a new fiber type replaced that Wellman fiber.

2. In 1971, West Point Pepperell sold 5,710 square yards of English Olive “Luxaire” and “Dreamer” carpet to Region C (10 south- eastern states which include Georgia). “Dreamer” was a line of carpet similar to “Luxaire” but contained a less dense pile. In or- der to account for the carpet manufactured during 1971, but sold after that time, all of the “Luxaire” English Olive carpet sold dur- ing 1972 to Region C (10,687 square yards) was added to the 1971 sales. Therefore, it was estimated that a total of 16,397 square yards of carpet containing the Wellman 181B fiber and dyed English Olive in color was sold by the West Point Pepperell Corporation to retailers in 10 southeastern states during 1971 and 1972. (In 1979, existing residential carpeted floor space in the United States was estimated at 6.7 billion square yards.)3

3. By assuming that this carpet was installed in one room, aver- aging 12 feet by 15 feet in size, per house, and also assuming that the total sales of carpet were divided equally among the 10 southeastern states, then approximately 82 rooms with this carpet could be found in the state of Georgia.

5 Information about carpet similar to Williams’s carpet was developed through contacts with carpet manufacturers and carpet salesmen in Georgia. It was determined that this type of carpet was often installed in commercial settings, such as apartments, and in those settings, had an average life span of 4 to 5 years.

4 Information regarding the number of housing units in the Atlanta metropol- itan area was obtained from a report provided by the Atlanta Regional Com- mission. The report, dated November 11, 1981, contained population and housing counts for counties, super districts, and census tracts in the Atlanta metropolitan area.

3 This information was taken from a study by E. I. du Pont de Nemours & Co. concerned with the existing residential floor space with carpet in the United States. This study was reported in a marketing survey conducted by the Marketing Corporation of America, Westport, Conn.

2 J. Mitchell and D. Holland, “An Unusual Case of Identification of Trans- ferred Fibers,” Journal of the Forensic Science Society, vol. 19, 1979, p. 23. This article describes a case in which carpet fibers transferred to a murder victim’s body in England were traced back to the carpet manufacturer and finally to an automobile owned by the person who eventually confessed to the murder.

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throwing a particular number would be one chance in six. The probability of throwing a second die and getting that same num- ber also would be one chance in six. However, the probability of getting 2 of the same numbers on 2 dice thrown simultaneously is only 1 in every 36 double throws—a much smaller chance than with either of the single throws. This number is a result of the product rule of probability theory. That is, the probability of the joint occurrence of a number of mutually independent events equals the product of the individual probabilities of each of the events (in this example—1⁄6 � 1⁄6 � 1⁄36). Since numerous fiber types are in existence, the chance of finding one particular fiber type, other than a common type, in a specific randomly selected location is small. The chance then of finding several fiber types together in a specific location is the product of several small probabilities, resulting in an extremely small chance. . . .

However, no attempt was made to use the product rule and multiply the individual probability numbers together to get an ap- proximation of the probability of finding carpets like Williams’s residential carpet and Williams’s automobile carpet in the same household. The probability numbers were used only to show that the individual fiber types involved in these associations were very uncommon. . . .6

In addition to the two probability numbers already discussed (bedroom and station wagon carpets), each of the other fiber types linking Williams to both Cater and Payne has a probability of be- ing found in a particular location. The chance of finding all of the fiber types indicated on the chart [Figure 1] in one location (seven types on Payne’s body and six types on Cater’s body) would be extremely small. Although an actual probability number for those findings could not be determined, it is believed that the multiple

or both of the victims are shown in the center of the chart. (See Figure 1.) Not only is Payne linked to Williams’s environment by seven items and Cater linked by six items, but both of the victims are linked strongly to each other based on the fiber matches and circumstances surrounding their deaths.

In discussing the significance or strength of an association based on textile fibers, it was emphasized that the more uncom- mon the fibers, the stronger the association. None of the fiber types from the items in Williams’s environment shown in the cen- ter of Figure 1 is by definition a “common” fiber type. Several of the fiber types would be termed “uncommon.”

One of the fibers linking the body of Jimmy Ray Payne to the carpet in the 1970 station wagon driven by Williams was a small rayon fiber fragment recovered from Payne’s shorts. Data were ob- tained from the station wagon’s manufacturer concerning which automobile models produced prior to 1973 contained carpet made of this fiber type. These data were coupled with additional infor- mation from Georgia concerning the number of these models reg- istered in the Atlanta metropolitan area during 1981. This allowed a calculation to be made relating to the probability of randomly se- lecting an automobile having carpet like that in the 1970 Chevro- let station wagon from the 2,373,512 cars registered in the Atlanta metropolitan area. This probability is 1 chance in 3,828, a very low probability representing a significant association.

Another factor to consider when assessing the significance of fiber evidence is the increased strength of the association when multiple fiber matches become the basis of the association. This is true if different fiber types from more than one object are found and each fiber type either links two people together or links an in- dividual with a particular environment. As the number of differ- ent objects increases, the strength of an association increases dramatically. That is, the chance of randomly finding several par- ticular fiber types in a certain location is much smaller than the chance of finding one particular fiber type.

The following example can be used to illustrate the signifi- cance of multiple fiber matches linking two items together. If one were to throw a single die one time, the chance or probability of

6 Joseph L. Peterson, ed., Forensic Science (New York: AMS Press, 1975), pp. 181–225. This collection of articles, dealing with various aspects of forensic science, contains five papers concerned with using statistics to interpret the meaning of physical evidence. It is a good discussion of probability theory and reviews cases where probability theory has been used in trial situations.

STATION WAGON: CARPET THROW RUG BLUE RAYON FIBERS

ITEMS FROM RESIDENCE AND STATION WAGON OF WAYNE WILLIAMS

JIMMY RAY PAYNE

Black male (21) 5'7", 135 lbs. Body recovered Chattahoochee River near I–85, 4/27/81 Death by Asphyxiation

NATHANIEL CATER

Black male (28) 5'11", 146 lbs. Body recovered Chattahoochee River near I–85, 5/24/81 Death by Asphyxiation

BACKROOM: CARPET SQUARE YELLOW-GREEN SYNTHETIC FIBERS

BEDROOM: BEDSPREAD BEDROOM CARPET BLANKET FROM UNDER BED WILLIAMS FAMILY DOG

FIGURE 1 Items from residence and station wagon of Wayne Williams that were found on Jimmy Ray Payne and Nathaniel Cater.

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victims whose murders were similar in many respects. Georgia law allows evidence of another crime to be introduced “. . . if some logical connection can be shown between the two from which it can be said that proof of the one tends to establish the other as relevant to some fact other than general bad character.”8

There need be no conviction for the other crime in order for de- tails about that crime to be admissible.

It was ruled that evidence concerning other murders could be introduced in an attempt to prove a “pattern or scheme” of killing that included the two murders with which Williams was charged. The additional evidence in these cases was to be used to help the jury “. . . decide whether Williams had committed the two mur- ders with which he is charged.”9

There were similarities between these additional victims and Payne and Cater. (See Figure 2.) Although some differences can also be seen on this chart, the prosecution considered these dif- ferences to fit within the “pattern of killing” of which Payne and Cater were a part. The most important similarities between these additional victims were the fiber matches that linked 9 of the 10 victims to Williams’s environment. The fiber findings discussed during the trial and used to associate Williams to the 12 victims were illustrated during the trial. (See Figure 3.)

The 12 victims were listed in chronological order based on the dates their bodies were recovered. The time period covered by this chart, approximately 22 months, is from July 1979 until May 1981. During that time period, the Williams family had ac- cess to a large number of automobiles, including a number of rental cars. Three of these automobiles are listed at the top of Figure 3. If one or more of the cars was in the possession of the Williams family at the time a victim was found to be missing, the space under that car(s) and after the particular victim’s name is shaded.

Four objects (including the dog) from Williams’s residence are listed horizontally across the top of Figure 3, along with ob- jects from three of his automobiles. An “X” on the chart indicates an apparent transfer of textile fibers from the listed object to a vic- tim. Other objects from Williams’s environment which were linked to various victims by an apparent fiber transfer are listed on the right side of the chart. Fiber types from objects (never ac- tually located) that were matched to fiber types from one or more victims are also listed either at the top or on the right side of the chart. Fourteen specific objects and five fiber types (probably from five other objects) listed on this chart are linked to one or more of the victims. More than 28 different fiber types, along with the dog hairs, were used to link up to 19 objects from Williams’s environment to 1 or more of the victims. Of the more than 28 fiber types from Williams’s environment, 14 of these originated from a rug or carpet.

The combination of more than 28 different fiber types would not be considered so significant if they were primarily common fiber types. In fact, there is only 1 light green cotton fiber of the 28 that might be considered common. This cotton fiber was blended with acetate fibers in Williams’s bedspread. Light green cotton fibers removed from many victims were not considered or compared unless they were physically intermingled with violet acetate fibers which were consistent with originating from the

fiber associations shown on this chart are proof that Williams is linked to the bodies of these two victims, even though each fiber match by itself does not show a positive association with Williams’s environment.

Studies have been conducted in England that show that trans- ferred fibers are usually lost rapidly as people go about their daily routine.7 Therefore, the foreign fibers present on a person are most often from recent surroundings. The fibrous debris found on a murder victim reflects the body’s more recent surroundings, es- pecially important if the body was moved after the killing. Ac- cordingly, the victims’ bodies in this particular case are not only associated with Williams but are apparently associated with Williams shortly before or after their deaths. It was also pointed out during the trial that the locations of the fibers—on Payne’s shorts and in Cater’s head hairs and pubic hairs—were not those where one would expect to find fibrous debris transferred from an automobile or a house to victims who had been fully clothed.

Although from these findings it would appear that the victims were in the residence of Williams, there was one other location that contained many of the same fibers as those in the composi- tion of various objects in his residence—Williams’s station wagon. The environment of a family automobile might be ex- pected to reflect, to some extent, fibers from objects located within the residence. This was true of the 1970 station wagon. With one exception, all of the fiber types removed from Payne and Cater, consistent with originating from items shown in the center of Figure 1, were present in debris removed by vacuuming the station wagon. The automobile would be the most logical source of the foreign fibers found on both Payne and Cater if they were associated with Williams shortly before or after their deaths. It should also be pointed out that two objects, the bedspread and the blanket, were portable and could have at one time been pres- ent inside the station wagon.

Both Payne and Cater were recovered from the Chatta- hoochee River. Their bodies had been in the water for several days. Some of the fibers found on these victims were like fibers in the compositions of the bedroom carpet and bedspread except for color intensity. They appeared to have been bleached. By sub- jecting various known fibers to small amounts of Chattahoochee River water for different periods of time, it was found that bleach- ing did occur. This was especially true with the carpet and bed- spread fibers from Williams’s bedroom.

Two crime laboratory examiners testified during the closing stages of the first part of the trial about Williams’s association with Payne and Cater. They concluded that it was highly unlikely that any environment other than that present in Wayne Williams’s house and car could have resulted in the combination of fibers and hairs found on the victims and that it would be virtually impossi- ble to have matched so many fibers found on Cater and Payne to items in Williams’s house and car unless the victims were in con- tact with or in some way associated with the environment of Wayne Williams.

After testimony was presented concerning the Payne and Cater cases, the Fulton County District Attorney’s Office asked the court to be allowed to introduce evidence in the cases of 10 other

7 C. A. Pounds and K. W. Smalldon, “The Transfer of Fibers between Cloth- ing Materials during Simulated Contacts and Their Persistence during Wear,” Journal of the Forensic Science Society, vol. 15, 1975, pp. 29–37.

9 The Atlanta Constitution, “Williams Jury Told of Other Slayings,” Sec. 1-A, 1/26/82, p. 25.

8 Encyclopedia of Georgia Law, vol. 11A (The Harrison Company, 1979), p. 70.

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bedspread. It should be noted that a combination of cotton and ac- etate fibers blended together in a single textile material, as in the bedspread, is in itself uncommon. . . .

The previous discussion concerning the significance of mul- tiple fiber matches can be applied to the associations made in the cases of all the victims except Bell, but especially to the associ- ation of Patrick Baltazar to Williams’s environment. Fibers and animal hairs consistent with having originated from 10 sources were removed from Baltazar’s body. These 10 sources include the uncommon bedroom carpet and station wagon carpet. In ad- dition to the fiber (and animal hair) linkage, two head hairs of Negroid origin were removed from Baltazar’s body that were consistent with originating from the scalp area of Williams. Head hair matches were also very significant in linking Williams to Baltazar’s body. In the opinion of the author, the association based upon the hair and fiber analyses is a positive association.

Another important aspect of the fiber linkage between Williams and these victims is the correspondence between the fiber findings and the time periods during which Williams had ac- cess to the three automobiles listed on the chart. Nine victims are linked to automobiles used by the Williams family. When Williams did not have access to a particular car, no fibers were

recovered that were consistent with having originated from that automobile. Trunk liner fibers of the type used in the trunks of many late-model Ford Motor Company automobiles were also re- covered from the bodies of two victims.

One final point should be made concerning Williams’s bed- room and station wagon carpets where probability numbers had been determined. Fibers consistent with having originated from both of these “unusual” carpets were recovered from Payne’s body. Of the 9 victims who were killed during the time period when Williams had access to the 1970 station wagon, fibers consistent with having originated from both the station wagon carpet and the bedroom carpet were recovered from 6 of these victims.

The apparent bleaching of several fibers removed from the bodies of Payne and Cater was consistent with having been caused by river water. Several fibers similar to those from Payne and Cater were removed from many of the victims whose bodies were recovered on land. Consistent with the bleaching argument, none of the fibers from the victims found on land showed any ap- parent bleaching. The finding of many of the same fiber types on the remaining victims, who were recovered from many different locations, refutes the possibility that Payne’s and Cater’s bodies picked up foreign fibers from the river.

90 CHAPTER 3

VICTIM’S NAME DATE VICTIM

MISSING DAYS

MISSING BODY

RECOVERY AREA CAUSE

OF DEATH AGE WEIGHT HEIGHT

EVANS 7/25/79 3

WOODED AREA S.W. ATLANTA

NEAR STREET S.E. ATLANTA

PROBABLE ASPHYXIATION/ STRANGULATION BLUNT TRAUMA

TO HEAD

87 LBS.

88 LBS.

5'4"

4'10"5/18/80

10/9/80

1/3/81

NEAR STREET S.E. ATLANTA

WOODED AREA FULTON COUNTY

1/22/81 1 NEAR HIGHWAY ROCKDALE CO.

ASPHYXIATION

MANUAL STRANGULATION

LIGATURE STRANGULATION

120 LBS.

130 LBS.

15 105 LBS.

5'0"

5'4"

5'5"

MIDDLEBROOKS

STEPHENS

GETER

PUE

2/6/81 7 NEAR HIGHWAY DEKALB CO.

LIGATURE STRANGULATION

12 125 LBS. 5'4"BALTAZAR

3/2/81 31 SOUTH RIVER DEKALB CO.

ASPHYXIATION 16 100 LBS. 5'2"BELL

3/30/81 10 NEAR STREET N.W. ATLANTA

ASPHYXIATION/ STRANGULATION

20 110 LBS. 5'3"ROGERS

4/10/81 1 NEAR STREET S.W. ATLANTA

STABBING 28 123 LBS. 5'7"PORTER

4/22/81 5 CHATTAHOOCHEE RIVER

FULTON COUNTY

ASPHYXIATION 21 135 LBS. 5'7"PAYNE

5/21/81 3 CHATTAHOOCHEE RIVER

FULTON COUNTY

ASPHYXIATION/ STRANGULATION

28 146 LBS. 5'11"CATER

5/11/81 1 NEAR STREET DEKALB CO.

LIGATURE STRANGULATION

(3 PUNCTURE WOUNDS)

17 125 LBS. 5'4"BARRETT

FIGURE 2 Chart used during the trial to show similarities between Payne and Cater and 10 other murder victims.

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PHYSICAL EVIDENCE 91

The fact that many of the victims were involved with so many of the same fiber types, all of which linked the victims to Williams’s environment, is the basis for arguing conclusively against these fibers originating from a source other than Williams’s environment.

It is hoped that this article has provided valuable insight con- cerning the use of fiber evidence in a criminal trial, has provided

answers to questions from those in the law enforcement commu- nity about textile fiber evidence in general, and has presented convincing arguments to establish Wayne Williams’s association with the bodies of the murder victims.

ADDITIONAL ITEMS FROM WILLIAMS’ HOME, AUTOMOBILES

OR PERSON

YELLOW NYLON

FORD TRUNK LINER

FORD TRUNK LINER WHITE POLYESTER

WHITE POLYESTER

BACKROOM CARPET

BACKROOM CARPET YELLOW-GREEN SYNTHETIC

HEAD HAIR GLOVE

GLOVE

JACKET PIGMENTED POLYPROPYLENE

PORCH BEDSPREAD

BLUE THROW RUG

CA RP

19 70

CH EV

RO LE

CA RP

19 79

FO RD

TR UN

K L INE

19 78

PL YM

OU TH

BL UE

RA YO

N FIB

ER S,

DE BR

FR OM

W ILL

IAM S’

HO ME

YE LLO

W BL

AN KE

WI LLI

AM S’

BE DR

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DO G

HA IRS

WI LLI

AM S’

DO G

GR EE

N CA

RP ET

WI LLI

AM S’

BE DR

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VIO LE

T-G RE

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WI LLI

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NAME OF VICTIM

Alfred Evans

Eric Middlebrooks

Charles Stephens

Lubie Geter

Terry Pue

Patrick Baltazar

Joseph Bell

Larry Rogers

John Porter

Jimmy Payne

William Barrett

Nathaniel Cater

� � �

�

� �

�

� �

�

� �

�

KITCHEN CARPET

FIGURE 3 Fiber findings discussed during the trial and used to associate Williams with the 12 victims.

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Murder and the Horse Chestnut Tree

Roger Severs was the son of a wealthy English couple, Eileen and Derek Severs. The elder Severses were reported missing in 1983. Police investigators were greeted at the Severs home by Roger, who at first 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 signs of blood spatter were on the garage door. Curiously, a number of green fibers 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 presence 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, investigators 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 capacity and found him guilty of murder.

headline news

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After studying this chapter you should be able to: • Define and distinguish the physical and chemical properties

of matter

• Understand how to use the basic units of the metric system

• Define and understand the properties of density and refractive index

• Understand and explain the dispersion of light through a prism

• List and explain forensic methods for comparing glass fragments

• Understand how to examine glass fractures to determine the direction of impact for a projectile

• List the important forensic properties of soil

• Describe the proper collection of glass and soil evidence

physical properties: glass and soil

amorphous solid atom Becke line birefringence Celsius scale chemical property concentric fracture crystalline solid density dispersion Fahrenheit scale intensive property laminated glass mass mineral physical property radial fracture refraction refractive index tempered glass weight

KEY TERMS

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chemical property The behavior of a substance when it reacts or combines with another substance

physical property The behavior of a substance without alteration of the substance’s composition through a chemical reaction

94 CHAPTER 4

Prefix Equivalent Value

deci- 1/10 or 0.1 centi- 1/100 or 0.01 milli- 1/1000 or 0.001 micro- 1/100,000 or 0.000001 nano- 1/1,000,000,000 or 0.000000001 kilo- 1,000 mega- 1,000,000

The forensic scientist must constantly determine the properties that impart distinguishing char- acteristics to matter, giving it a unique identity. The continuing search for distinctive properties ends only when the scientist has completely individualized a substance to one correct source. Properties are the identifying characteristics of substances. In this and succeeding chapters, we will examine properties that are most useful for characterizing soil, glass, and other physical ev- idence. However, before we begin, we can simplify our understanding of the nature of properties by classifying them into two broad categories: physical and chemical.

Physical properties describe a substance without reference to any other substance. For example, weight, volume, color, boiling point, and melting point are typical physical properties that can be measured for a particular substance without altering the material’s composition through a chemical reaction; they are associated only with the physical existence of that sub- stance. A chemical property describes the behavior of a substance when it reacts or combines with another substance. For example, when wood burns, it chemically combines with oxygen in the air to form new substances; this transformation describes a chemical property of wood. In the crime laboratory, a routine procedure for determining the presence of heroin in a suspect spec- imen is to react it with a chemical reagent known as the Marquis reagent, which turns purple in the presence of heroin. This color transformation becomes a chemical property of heroin and pro- vides a convenient test for its identification.

Which physical and chemical properties the forensic scientist ultimately chooses to observe and measure depends on the type of material that is being examined. Logic requires, however, that if the property can be assigned a numerical value, it must relate to a standard system of mea- surement accepted throughout the scientific community.

The Metric System Although scientists, including forensic scientists, throughout the world have been using the metric system of measurement for more than a century, the United States still uses the cum- bersome “English system” to express length in inches, feet, or yards; weight in ounces or pounds; and volume in pints or quarts. The inherent difficulty of this system is that no sim- ple numerical relationship exists between the various units of measurement. For example, to convert inches to feet one must know that 1 foot equals 12 inches; conversion of ounces to pounds requires the knowledge that 16 ounces equals 1 pound. In 1791, the French Academy of Science devised the simple system of measurement known as the metric system. This system uses a simple decimal relationship so that a unit of length, volume, or mass can be converted into a subunit by simply multiplying or dividing by a multiple of 10—for example, 10, 100, or 1,000.

Even though the United States has not yet adopted the metric system, its system of currency is decimal and, hence, is analogous to the metric system. The basic unit of currency is the dollar. A dollar is divided into 10 equal units called dimes, and each dime is further divided into 10 equal units of cents.

Basic Units of Measurement The metric system has basic units of measurement for length, mass, and volume: the meter, gram, and liter, respectively. These three basic units can be converted into subunits that are decimal mul- tiples of the basic unit by simply attaching a prefix to the unit name. The following are common prefixes and their equivalent decimal value:

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PHYSICAL PROPERTIES: GLASS AND SOIL 95

10 cm

1 cm

10 cm 1 cm 3 = 1mL

1 liter (1 L) = 1,000 cm 3

1,000 mL

FIGURE 4–1 Volume equivalencies in the metric system.

1 2 3 4 5 6 7 8 9 10 11

21 3 4

FIGURE 4–2 Comparison of the metric and English systems of length measurement; 2.54 centimeters � 1 inch.

Hence, 1/10 or 0.1 gram (g) is the same as a decigram (dg), 1/100 or 0.01 meter is equal to a centimeter (cm), and 1/1,000 liter is a milliliter (mL). A metric conversion is carried out simply by moving the decimal point to the right or left and inserting the proper prefix to show the direc- tion and number of places that the decimal point has been moved. For example, if the weight of a powder is 0.0165 gram, it may be more convenient to multiply this value by 100 and express it as 1.65 centigrams or by 1,000 to show it as its equivalent value of 16.5 milligrams. Similarly, an object that weighs 264,450 grams may be expressed as 264.45 kilograms simply by dividing it by 1,000. It is important to remember that in any of these conversions, the value of the measurement has not changed; 0.0165 gram is still equivalent to 1.65 centigrams, just as one dollar is still equal to 100 cents. We have simply adjusted the position of the decimal and shown the extent of the ad- justment with a prefix.

One interesting aspect of the metric system is that volume can be defined in terms of length. A liter by definition is the volume of a cube with sides of length 10 centimeters. One liter is there- fore equivalent to a volume of 10 cm � 10 cm � 10 cm, or 1,000 cubic centimeters (cc). Thus, 1/1,000 liter or 1 milliliter (mL) is equal to 1 cubic centimeter (cc) (see Figure 4–1). Scientists commonly use the subunits mL and cc interchangeably to express volume.

Metric Conversion At times, it may be necessary to convert units from the metric system into the English system, or vice versa (see Figure 4–2). To accomplish this, we must consult references that list English units and their metric equivalents. Some of the more useful equivalents follow:

1 inch � 2.54 centimeters 1 meter � 39.37 inches 1 pound � 453.6 grams 1 liter � 1.06 quarts 1 kilogram � 2.2 pounds

The general mathematical procedures for converting from one system to another can be il- lustrated by converting 12 inches into centimeters. To change inches into centimeters, we need to know that there are 2.54 centimeters per inch. Hence, if we multiply 12 inches by 2.54 centime- ters per inch (12 in. � 2.54 cm/in.), the unit of inches will cancel out, leaving the product

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mass A constant property of matter that reflects the amount of material present

weight A property of matter that depends on both the mass of a substance and the effects of gravity on that mass

Celsius scale The temperature scale using the melting point of ice as 0° and the boiling point of water as 100°, with 100 equal divisions or degrees between

Fahrenheit scale The temperature scale using the melting point of ice as 32° and the boiling point of water as 212°, with 180 equal divisions or degrees between

96 CHAPTER 4

FIGURE 4–3 Comparison of the Celsius and Fahrenheit temperature scales.

30.48 cm. Similarly, applying the conversion of grams to pounds, 227 grams is equivalent to 227 g � 1 lb/453.6 g or 0.5 lb.

Physical Properties All materials possess a range of physical properties whose measurement is critical to the work of the forensic scientist. Several of the most important of these are temperature, weight, mass, den- sity, and refractive index.

Temperature Determining the physical properties of any material often requires measuring its temperature. For instance, the temperatures at which a substance melts or boils are readily determinable charac- teristics that will help identify it. Temperature is a measure of heat intensity, or the amount of heat in a substance.

Temperature is usually measured by causing a thermometer to come into contact with a sub- stance. The familiar mercury-in-glass thermometer functions because mercury expands more than glass when heated and contracts more than glass when cooled. Thus, the length of the mer- cury column in the glass tube provides a measure of the surrounding environment’s temperature.

The construction of a temperature scale requires two reference points and a choice of units. The reference points most conveniently chosen are the freezing point and boiling point of water. The two most common temperature scales used are the Fahrenheit and Celsius (formerly called centigrade) scales.

The Fahrenheit scale is based on assigning a value of 32°F to the freezing point of water and a value of 212°F to its boiling point. The difference between the two points is evenly divided into 180 units. Thus, a degree Fahrenheit is 1/180 of the temperature change between the freezing point and boiling point of water. The Celsius scale is derived by assigning the freezing point of water a value of 0°C and its boiling point a value of 100°C. A degree Celsius is thus 1/100 of the temperature change between the two reference points. Scientists in most countries use the Cel- sius scale to measure temperature. A comparison of the two scales is shown in Figure 4–3.

Weight and Mass The force with which gravity attracts a body is called weight. If your weight is 180 pounds, this means that the earth’s gravity is pulling you down with a force of 180 pounds; on the moon, where the force of gravity is one-sixth that of the earth, your weight would be 30 pounds.

Mass differs from weight because it refers to the amount of matter an object contains and is independent of its location on earth or any other place in the universe. The mathematical rela- tionship between weight (w) and mass (m) is shown in Equation (4–1), where g is the accelera- tion imparted to a body by the force of gravity.

W � mg (4–1)

The weight of a body is directly proportional to its mass; hence, a large mass weighs more than a small mass.

In the metric system, the mass of an object is always specified, rather than its weight. The basic unit of mass is the gram. An object that has a mass of 40 grams on earth will have a mass of 40 grams anywhere else in this universe. Normally, however, the terms mass and weight are used interchangeably, and we often speak of the weight of an object when we really mean its mass.

The mass of an object is determined by comparing it against the known mass of standard ob- jects. The comparison is confusingly called weighing, and the standard objects are called weights (masses would be a more correct term). The comparison is performed on a balance. The simplest type of balance for weighing is the equal-arm balance shown in Figure 4–4. The object to be weighed is placed on the left pan, and the standard weights are placed on the right pan; when the pointer between the two pans is at the center mark, the total mass on the right pan is equal to the mass of the object on the left pan.

The modern laboratory has progressed beyond the simple equal-arm balance, and either the top-loading balance or the single-pan analytical balance (see Figure 4–5) is now likely to be used. The choice depends on the accuracy required and the amount of material being weighed. Each

-30º

-20º

-10º

0º

10º

20º

30º

40º

50º

60º

70º

80º

90º

100º

Celsius

-20º

0º

20º 32º 40º

60º

80º

100º

120º

140º

160º

180º

200º 212º

Fahrenheit

220º Boiling point of water

Normal body temperature

Normal room temperature

Freezing point of water

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PHYSICAL PROPERTIES: GLASS AND SOIL 97

Unknown masses

Known masses

FIGURE 4–4 The measurement of mass.

(a)

FIGURE 4–5 (a) Top-loading balance. (b) Single-pan analytical balance. (a) Courtesy of Ohaus Corporation (b) Courtesy Sirchie Fingerprint Laboratories, Youngsville, N.C., www.sirchie.com

(b)

works on the same counterbalancing principle as the simple equal-arm balance. Earlier versions of the single-pan balance had a second pan, the one on which the standard weights were placed. This pan was hidden from view within the balance’s housing. Once the object whose weight was to be determined was placed on the visible pan, the operator selected the proper standard weights (also contained within the housing) by manually turning a set of knobs located on the front side of the balance. At the point of balance, the weights selected were automatically recorded on op- tical readout scales. Modern single-pan balances rely on an electromagnetic field to generate a current to balance the force pressing down on the pan from the sample being weighed. When the scale is properly calibrated, the amount of current needed to keep the pan balanced is used to de- termine the weight of the sample. The strength of the current is converted to a digitized signal for a readout. The top-loading balance can accurately weigh an object to the nearest 1 milligram or 0.001 gram; the analytical balance is even more accurate, weighing to the nearest tenth of a milligram or 0.0001 gram.IS

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intensive property A property that is not dependent on the size of an object

density A physical property of matter that is equivalent to the mass per unit volume of a substance

98 CHAPTER 4

TABLE 4–1 Densities of Select Materials (at 20°C unless otherwise stated)

Substance Density (g/mL)

Solids Silver 10.5 Lead 11.5 Iron 7.8 Aluminum 2.7 Window glass 2.47–2.54 Ice (0°C) 0.92

Liquids Mercury 13.6 Benzene 0.88 Ethyl alcohol 0.79 Gasoline 0.69 Water at 4°C 1.00 Water 0.998

Gases Air (0°C) 0.0013 Chlorine (0°C) 0.0032 Oxygen (0°C) 0.0014 Carbon dioxide (0°C) 0.0020

10Mass

Volume

FIGURE 4–6 A simple procedure for determining the density of a solid is to first weigh it and then measure its volume by noting the volume of water it displaces.

Density An important physical property of matter with respect to the analysis of certain kinds of physical evidence is density. Density is defined as mass per unit volume [see Equation (4–2)].

Density � mass

volume (4–2)

Density is an intensive property of matter—that is, it is the same regardless of the size of a substance; thus, it is a characteristic property of a substance and can be used as an aid in identi- fication. Solids tend to be more dense than liquids, and liquids more dense than gases. The den- sities of some common substances are shown in Table 4–1.

A simple procedure for determining the density of a solid is illustrated in Figure 4–6. First, the solid is weighed on a balance against known standard gram weights to determine its mass.

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PHYSICAL PROPERTIES: GLASS AND SOIL 99

The solid’s volume is then determined from the volume of water it displaces. This is easily mea- sured by filling a cylinder with a known volume of water (V1), adding the object, and measuring the new water level (V2). The difference V2 � V1 in milliliters is equal to the volume of the solid. Density can now be calculated from Equation (4–2) in grams per milliliter.

The volumes of gases and liquids vary considerably with temperature; hence, when determin- ing density, it is important to control and record the temperature at which the measurements are made. For example, 1 gram of water occupies a volume of 1 milliliter at 4°C and thus has a density of 1.0 g/mL. However, as the temperature of water increases, its volume expands. Therefore, at 20°C (room temperature) 1 gram of water occupies a volume of 1.002 mLand has a density of 0.998 g/mL.

The observation that a solid object either sinks, floats, or remains suspended when immersed in a liquid can be accounted for by the property of density. For instance, if the density of a solid is greater than that of the liquid in which it is immersed, the object sinks; if the solid’s density is less than that of the liquid, it floats; and when the solid and liquid have equal densities, the solid remains suspended in the liquid. As we will shortly see, these observations provide a convenient technique for comparing the densities of solid objects.

Refractive Index Light, as we will learn in the next chapter, can have the property of a wave. Light waves travel in air at a constant velocity of nearly 300 million meters per second until they penetrate another medium, such as glass or water, at which point they are suddenly slowed, causing the rays to bend. The bending of a light wave because of a change in velocity is called refraction.

The phenomenon of refraction is apparent when we view an object that is immersed in a transparent medium; because we are accustomed to thinking that light travels in a straight line, we often forget to take refraction into account. For instance, suppose a ball is observed at the bot- tom of a pool of water; the light rays reflected from the ball travel through the water and into the air to reach the eye. As the rays leave the water and enter the air, their velocity suddenly increases, causing them to be refracted. However, because of our assumption that light travels in a straight line, our eyes deceive us and make us think we see an object lying at a higher point than is actu- ally the case. This phenomenon is illustrated in Figure 4–7.

The ratio of the velocity of light in a vacuum to that in any medium determines the refractive index of that medium and is expressed as follows:

Refractive index � velocity of light in vacuum velocity of light in medium

For example, at 25°C the refractive index of water is 1.333. This means that light travels 1.333 times as fast in a vacuum as it does in water at this temperature.

Like density, the refractive index is an intensive physical property of matter and character- izes a substance. However, any procedure used to determine a substance’s refractive index must be performed under carefully controlled temperature and lighting conditions because the refractive index of a substance varies with its temperature and the wavelength of light passing through it. Nearly all tabulated refractive indices are determined at a standard wavelength,

refraction The bending of a light wave as it passes from one medium to another

Apparent position of ball

Air

Water

Ball

FIGURE 4–7 Light is refracted when it travels obliquely from one medium to another.

refractive index The ratio of the speed of light in a vacuum to its speed in a given substance

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dispersion The separation of light into its component wavelengths

birefringence A difference in the two indices of refraction exhibited by most crystalline materials

amorphous solid A solid in which the constituent atoms or molecules are arranged in random or disordered positions; there is no regular order in amorphous solids

atom The smallest unit of an element, which is not divisible by ordinary chemical means; atoms are made up of electrons, protons, and neutrons plus other subatomic particles

crystalline solid A solid in which the constituent atoms have a regular arrangement

100 CHAPTER 4

FIGURE 4–8 Diagram of a sodium chloride crystal. Sodium is represented by the darker spheres, chlorine by the lighter spheres.

usually 589.3 nanometers; this is the predominant wavelength emitted by sodium light and is commonly known as the sodium D light.

COMPARING REFRACTIVE INDICES When a transparent solid is immersed in a liquid with a similar refractive index, light is not refracted as it passes from the liquid into the solid. For this reason, the eye cannot distinguish the liquid–solid boundary, and the solid seems to disappear from view. This observation, as we will see, offers the forensic scientist a simple method for com- paring the refractive indices of transparent solids.

Normally, we expect a solid or a liquid to exhibit only one refractive index value for each wavelength of light; however, many crystalline solids have two refractive indices whose values depend in part on the direction in which the light enters the crystal with respect to the crystal axis. Crystalline solids have definite geometric forms because of the orderly arrangement of the fundamental particle of a solid, the atom. In any type of crystal, the relative locations and dis- tances between its atoms are repetitive throughout the solid. Figure 4–8 shows the crystalline structure of sodium chloride, or ordinary table salt. Sodium chloride is an example of a cubic crys- tal in which each sodium atom is surrounded by six chloride atoms and each chloride atom by six sodium atoms, except at the crystal surface. Not all solids are crystalline in nature; some, such as glass, have their atoms arranged randomly throughout the solid; these materials are known as amorphous solids.

Most crystals, excluding those that have cubic configurations, refract a beam of light into two different light-ray components. This phenomenon, known as double refraction, can be observed by studying the behavior of the crystal calcite. When the calcite is laid on a printed page, the ob- server sees not one but two images of each word covered. The two light rays that give rise to the double image are refracted at different angles, and each has a different refractive index value. The indices of refraction for calcite are 1.486 and 1.658, and subtracting the two values yields a dif- ference of 0.172; this difference is known as birefringence. Thus, the optical properties of crys- tals provide points of identification that help characterize them.

DISPERSION Many of us have held a glass prism up toward the sunlight and watched it trans- form light into the colors of the rainbow. This observation demonstrates that visible “white light” is not homogeneous but is actually composed of many different colors. The process of separating light into its component colors is called dispersion. The ability of a prism to disperse light into its component colors is explained by the property of refraction. Each color component of light, on passing through the glass, 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. As shown in Figure 4–9, the component colors of visible light extend from red to violet. We will learn in Chapter 5 that each color corresponds to a different range of wavelengths of light. Dispersion thus separates light into its component wavelengths and demonstrates that glass has a slightly different index of refraction for each wavelength of light passing through it.

Now that we have investigated various physical properties of objects, we are ready to apply such properties to the characterization of two substances—glass and soil—that commonly must be examined by the criminalist.

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PHYSICAL PROPERTIES: GLASS AND SOIL 101

Forensic Analysis of Glass Glass that is broken and shattered into fragments and minute particles during the commission of a crime can be used to place a suspect at the crime scene. For example, chips of broken glass from a window may lodge in a suspect’s shoes or garments during a burglary, or particles of headlight glass found at the scene of a hit-and-run accident may offer clues that can confirm the identity of a suspect vehicle. All of these possibilities require the comparison of glass fragments found on the suspect, whether a person or vehicle, with the shattered glass remaining at the crime scene.

Composition of Glass Glass is a hard, brittle, amorphous substance composed of sand (silicon oxides) mixed with var- ious metal oxides. When sand is mixed with other metal oxides, melted at high temperatures, and then cooled to a rigid condition without crystallization, the product is glass. Soda (sodium car- bonate) is normally added to the sand to lower its melting point and make it easier to work with. Another necessary ingredient is lime (calcium oxide), needed to prevent the “soda-lime” glass from dissolving in water. The forensic scientist is often asked to analyze soda-lime glass, which is used for manufacturing most window and bottle glass. Usually the molten glass is cooled on a bed of molten tin. This manufacturing process produces flat glass typically used for windows. This type of glass is called float glass.

In addition, a wide variety of special glasses can be made by substituting in whole or in part other metal oxides for the silica, sodium, and calcium oxides. For example, automobile headlights and heat-resistant glass, such as Pyrex, are manufactured by adding boron oxide to the oxide mix. These glasses are therefore known as borosilicates.

Another type of glass that the reader may be familiar with is tempered glass. This glass is made stronger than ordinary window glass by introducing stress through rapid heating and cool- ing of the glass surfaces. When tempered glass breaks, it does not shatter but rather fragments or “dices” into small squares with little splintering (see Figure 4–10). Because of this safety feature, tempered glass is used in the side and rear windows of automobiles made in the United States, as well as in the windshields of some foreign-made cars. The windshields of all cars manufactured in the United States are constructed from laminated glass. This glass derives its strength by sand- wiching one layer of plastic between two pieces of ordinary window glass.

Comparing Glass Fragments For the forensic scientist, comparing glass consists of finding and measuring the properties that will associate one glass fragment with another while minimizing or eliminating the possible existence of other sources. Considering the prevalence of glass in our society, it is easy to appre- ciate the magnitude of this analytical problem. Obviously, glass possesses its greatest evidential value when it can be individualized to one source. Such a determination, however, can be made only when the suspect and crime-scene fragments are assembled and physically fitted together. Comparisons of this type require piecing together irregular edges of broken glass as well as matching all irregularities and striations on the broken surfaces (see Figure 4–11). The possibil- ity that two pieces of glass originating from different sources will fit together exactly is so unlikely as to exclude all other sources from practical consideration.

White light

Slit

Prism

Screen

Red

Violet

Red

Violet

Orange Yellow

Green Blue

FIGURE 4–9 Representation of the dispersion of light by a glass prism.

laminated glass Two sheets of ordinary glass bonded together with a plastic film

tempered glass Glass that is strengthened by introducing stress through rapid heating and cooling of the glass surfaces

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FIGURE 4–10 When tempered glass breaks, it usually holds together without splintering. Courtesy Robert Llewellyn, Alamy Images

FIGURE 4–11 Match of broken glass. Note the physical fit of the edges. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

Unfortunately, most glass evidence is either too fragmentary or too minute to permit a comparison of this type. In such instances, the search for individual properties has proven fruit- less. For example, the general chemical composition of various window glasses within the ca- pability of current analytical methods has so far been found relatively uniform among various manufacturers and thus offers no basis for individualization. However, trace elements present in glass have been shown to be useful for narrowing the origin of a glass specimen. The phys- ical properties of density and refractive index are most widely used for characterizing glass particles. However, these properties are class characteristics, which cannot provide the sole criteria for individualizing glass to a common source. They do, however, give the analyst sufficient data to evaluate the significance of a glass comparison, and the absence of compa- rable density and refractive index values will certainly exclude glass fragments that originate from different sources.

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Measuring and Comparing Density Recall that a solid particle will either float, sink, or remain suspended in a liquid, depending on its density relative to the liquid. This knowledge gives the criminalist a rather precise and rapid method for comparing densities of glass. In a method known as flotation, a standard/reference glass particle is immersed in a liquid; a mixture of bromoform and bromobenzene may be used. The composition of the liquid is carefully adjusted by the addition of small amounts of bromoform or bromobenzene until the glass chip remains suspended in the liquid medium. At this point, the standard/reference glass and liquid each have the same density. Glass chips of approximately the same size and shape as the standard/reference are now added to the liquid for comparison. If both the unknown and the standard/reference particles remain suspended in the liquid, their densities are equal to each other and to that of the liquid.1 Particles of different densities either sink or float, depending on whether they are more or less dense than the liquid.

The density of a single sheet of window glass is not completely homogeneous throughout. It has a range of values that can differ by as much as 0.0003 g/mL. Therefore, in order to distinguish between the normal internal density variations of a single sheet of glass and those of glasses of different origins, it is advisable to let the comparative density approach but not exceed a sensi- tivity value of 0.0003 g/mL. The flotation method meets this requirement and can adequately distinguish glass particles that differ in density by 0.001 g/mL.

Determining and Comparing Refractive Index Once glass has been distinguished by a density determination, different origins are immediately concluded. Comparable density results, however, require the added comparison of refractive in- dices. This determination is best accomplished by the immersion method. For this, glass particles are immersed in a liquid medium whose refractive index is adjusted until it equals that of the glass particles. At this point, known as the match point, the observer notes the disappearance of the Becke line and minimum contrast between the glass and liquid medium. The Becke line is a bright halo that is observed near the border of a particle that is immersed in a liquid of a different refrac- tive index. This halo disappears when the medium and fragment have similar refractive indices.

The refractive index of an immersion fluid is best adjusted by changing the temperature of the liquid. Temperature control is, of course, critical to the success of the procedure. One approach to this procedure is to heat the liquid in a special apparatus known as a hot stage. The glass is immersed in a boiling liquid, usually a silicone oil, and heated at the rate of 0.2°C per minute until the match point is reached. Increasing the temperature of the liquid has a negligible effect on the refractive index of glass, whereas the liquid’s index decreases at the rate of approx- imately 0.0004 per degree Celsius. The hot stage, as shown in Figure 4–12, is designed to be used

Becke line A bright halo that is observed near the border of a particle immersed in a liquid of a different refractive index

FIGURE 4–12 Hot-stage microscope. Courtesy of Chris Palenik, Ph.D., Microtrace LLC, Elgin, IL.

1 As an added step, the analyst can determine the exact numerical density value of the particles of glass by transferring the liquid to a density meter, which will electrically measure and calculate the liquid’s density. See A. P. Beveridge and C. Semen, “Glass Density Measurement Using a Calculating Digital Density Meter,” Canadian Society of Foren- sic Science Journal 12 (1979): 113.

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in conjunction with a microscope, through which the examiner can observe the disappearance of the Becke line on minute glass particles that are illuminated with sodium D light or other wave- lengths of light. If all the glass fragments examined have similar match points, it can be concluded that they have comparable refractive indices (see Figure 4–13). Furthermore, the examiner can determine the refractive index value of the immersion fluid as it changes with temperature. With this information, the exact numerical value of the glass refractive index can be calculated at the match point temperature.2

An automated approach for measuring the refractive index of glass fragments by tempera- ture control using the immersion method with a hot stage is with the instrument known as GRIM 3 (glass refractive index measurement) (see Figure 4–14). The GRIM 3 is a personal computer/video system designed to automate the measurements of the match temperature and refractive index for glass fragments. This instrument uses a video camera to view the glass fragments as they are being heated. As the immersion oil is heated or cooled, the contrast of the video image is measured continually until a minimum, the match point, is detected (see Figure 4–15). The match point temperature is then converted to a refractive index using stored calibration data.

As with density, glass fragments removed from a single sheet of plate glass may not have a uniform refractive index value; instead, their values may vary by as much as 0.0002. Hence, for

(a)

FIGURE 4–13 Determination of the refractive index of glass. (a) Glass particles are immersed in a liquid of a much higher refractive index at a temperature of 77°C. (b) At 87°C the liquid still has a higher refractive index than the glass. (c) The refractive index of the liquid is closest to that of the glass at 97°C, as shown by the disappearance of the glass and the Becke lines. (d) At the higher temperature of 117°C, the liquid has a much lower index than the glass, and the glass is plainly visible. Courtesy Walter C. McCrone

(b)

2 A. R. Cassista and P. M. L. Sandercock, “Precision of Glass Refractive Index Measurements: Temperature Variation and Double Variation Methods, and the Value of Dispersion,” Canadian Society of Forensic Science Journal 27 (1994): 203.

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FIGURE 4–14 An automated system for glass fragment identification. Courtesy Foster & Freeman Limited, Worcestershire, U.K., www.fosterfreeman.co.uk

FIGURE 4–15 GRIM 3 identifies the refraction match point by monitoring a video image of four different areas of the glass fragment immersed in an oil. As the immersion oil is heated or cooled, the contrast of the image is measured continuously until a minimum, the match point, is detected. Courtesy Foster & Freeman Limited, Worcestershire, U.K., www.fosterfreeman.co.uk

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120

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1.5100 1.5110

1.5120 1.5130

1.5140 1.5150

1.5160 1.5170

1.5180 1.5190

1.5200 1.5210

1.5220 1.5230

1.5240 1.5250

1.5260 1.5270

1.5280 1.5290

1.5300

Refractive index

FIGURE 4–16 Frequency of occurrence of refractive index values (measured with sodium D light) for approximately two thousand flat glass specimens received by the FBI Laboratory. Courtesy FBI Laboratory, Washington, D.C.

comparison purposes, the difference in refractive index between a standard/reference and ques- tioned glass must exceed this value. This allows the examiner to differentiate between the normal internal variations present in a sheet of glass and those present in glasses that originated from completely different sources.

Classification of Glass Samples A significant difference in either density or refractive index proves that the glasses examined do not have a common origin. But what if two pieces of glass exhibit comparable densities and com- parable refractive indices? How certain can one be that they did, indeed, come from the same source? After all, there are untold millions of windows and other glass objects in this world. To provide a reasonable answer to this question, the FBI Laboratory has collected density and refrac- tive index values from glass submitted to it for examination. What has emerged is a data bank cor- relating these values to their frequency of occurrence in the glass population of the United States. This collection is available to all forensic laboratories in the United States.

Once a criminalist has completed a comparison of glass fragments, he or she can correlate their density and refractive index values to their frequency of occurrence and assess probability that the fragments came from the same source. Figure 4–16 shows the distribution of refractive index values (measured with sodium D light) for approximately two thousand glasses analyzed by the FBI. The wide distribution of values clearly demonstrates that the refractive index is a highly distinctive property of glass and is thus useful for defining its frequency of occurrence and hence its evidential value. For example, a glass fragment with a refractive index value of 1.5290 is found in approximately only 1 out of 2,000 specimens, whereas glass with a value of 1.5180 occurs approximately in 22 glasses out of 2,000.

Although refractive index and density have been routinely used for the comparison of glass for some time, forensic scientists have long desired to extract additional information from glass

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fragments that would make their comparison more meaningful. The trace elemental composition of glass held a longtime attraction to forensic scientists for this purpose. However, until recently, the an- alytical instrumentation sensitive enough to develop a trace elemental profile from a glass fragment was too costly for most crime laboratories. This handicap has been overcome with the introduction of a technique that aims a high-energy laser pulse to vaporize a microscopic amount of glass, raising its temperature by thousands of degrees.As a result, the elements present in the glass are induced to emit light whose wavelengths correspond to the identity of the elements present (see Figure 4–17).

The distinction between tempered and nontempered glass particles can be made by slowly heating and then cooling the glass (a process known as annealing). The change in the refractive index value for tempered glass upon annealing is significantly greater when compared to nontempered glass and thus serves as a point of distinction.3

Glass Fractures Glass bends in response to any force exerted on any one of its surfaces; when the limit of its elasticity is reached, the glass fractures. Frequently, fractured window glass reveals information that can be related to the force and direction of an impact; such knowledge may be useful for reconstructing events at a crime-scene investigation.

The penetration of ordinary window glass by a projectile, whether a bullet or a stone, pro- duces a familiar fracture pattern in which cracks both radiate outward and encircle the hole, as shown in Figure 4–18. The radiating lines are appropriately known as radial fractures, and the circular lines are termed concentric fractures.

Often it is difficult to determine just from the size and shape of a hole in glass whether it was made by a bullet or by some other projectile. For instance, a small stone thrown at a comparatively

FIGURE 4–17 The elemental profile of a glass fragment is obtained by aiming a high-energy laser beam at a glass particle, inducing the emission of light wavelengths corresponding to the identity of the elements present in the glass. Courtesy Foster & Freeman Limited, Worcestershire, U.K., www.fosterfreeman.co.uk

radial fracture A crack in a glass that extends outward like the spoke of a wheel from the point at which the glass was struck

concentric fracture A crack in a glass that forms a rough circle around the point of impact

3 G. Edmondstone, “The Identification of Heat Strengthened Glass in Windshields,” Canadian Society of Forensic Science Journal 30 (1997): 181.

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high speed against a pane of glass often produces a hole similar to that produced by a bullet. On the other hand, a large stone can completely shatter a pane of glass in a manner closely resembling the result of a close-range shot. However, in the latter instance, the presence of gunpowder de- posits on the shattered glass fragments points to damage caused by a firearm.

When it penetrates glass, a high-velocity projectile such as a bullet often leaves a round, crater- shaped hole surrounded by a nearly symmetrical pattern of radial and concentric cracks. The hole is inevitably wider on the exit side (see Figure 4–19), and hence examining it is an important step in determining the direction of impact. However, as the velocity of the penetrating projectile de- creases, the irregularity of the shape of the hole and of its surrounding cracks increases, so that at some point the hole shape will not help determine the direction of impact. At this time, examining the radial and concentric fracture lines may help determine the direction of impact.

When a force pushes on one side of a pane of glass, the elasticity of the glass permits it to bend in the direction of the force applied. Once the elastic limit is exceeded, the glass begins to crack. As shown in Figure 4–20, the first fractures form on the surface opposite that of the pene- trating force and develop into radial lines. The continued motion of the force places tension on the front surface of the glass, resulting in the formation of concentric cracks. An examination of the edges of the radial and concentric cracks frequently reveals stress markings (Wallner lines) whose shape can be related to the side on which the window first cracked.

FIGURE 4–18 Radial and concentric fracture lines in a sheet of glass. Courtesy Sirchie Finger Print Laboratories, Youngsville, N.C., www.sirchie.com

FIGURE 4–19 Crater-shaped hole made by a bullet passing through glass. The upper surface is the exit side of the projectile. Courtesy Don Farrall, Getty Images, Inc. Photodisc/Royalty Free

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Stress marks, shown in Figure 4–21, are shaped like arches that are perpendicular to one glass surface and curved nearly parallel to the opposite surface. The importance of stress marks stems from the observation that the perpendicular edge always faces the surface on which the crack orig- inated. Thus, in examining the stress marks on the edge of a radial crack near the point of impact, the perpendicular end is always found opposite the side from which the force of impact was applied. For a concentric fracture, the perpendicular end always faces the surface on which the force originated. A convenient way for remembering these observations is the 3R rule—Radial cracks form a Right angle on the Reverse side of the force. These facts enable the examiner to determine the side on which a window was broken. Unfortunately, the absence of radial or con- centric fracture lines prevents these observations from being applied to broken tempered glass.

When there have been successive penetrations of glass, it is frequently possible to determine the sequence of impact by observing the existing fracture lines and their points of termination. A fracture always terminates at an existing line of fracture. In Figure 4–22, the fracture on the left preceded that on the right; we know this because the latter’s radial fracture lines terminate at the cracks of the former.

(a) (b)

FIGURE 4–20 Production of radial and concentric fractures in glass. (a) Radial cracks are formed first, commencing on the side of the glass opposite to the destructive force. (b) Concentric cracks occur afterward, starting on the same side as the force.

FIGURE 4–21 Stress marks on the edge of a radial glass fracture. Arrow indicates direction of force.

FIGURE 4–22 Two bullet holes in a piece of glass. The left hole preceded the right hole.

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Collection and Preservation of Glass Evidence The gathering of glass evidence at the crime scene and from the suspect must be thorough if the examiner is to have any chance to individualize the fragments to a common source. If even the re- motest possibility exists that fragments may be pieced together, every effort must be made to collect all the glass found. For example, evidence collection at hit-and-run scenes must include all the bro- ken parts of the headlight and reflector lenses. This evidence may ultimately prove invaluable in placing a suspect vehicle at the accident scene by matching the fragments with glass remaining in the headlight or reflector shell of the suspect vehicle. In addition, examining the headlight’s filaments may reveal whether an automobile’s headlights were on or off before the impact (see Figure 4–23).

When an individual fit is improbable, the evidence collector must submit all glass evidence found in the possession of the suspect along with a sample of broken glass remaining at the crime scene. This standard/reference glass should always be taken from any remaining glass in the win- dow or door frames, as close as possible to the point of breakage. About one square inch of sam- ple is usually adequate for this purpose. The glass fragments should be packaged in solid containers to avoid further breakage. If the suspect’s shoes and/or clothing are to be examined for the presence of glass fragments, they should be individually wrapped in paper and transmitted to the laboratory. The field investigator should avoid removing such evidence from garments unless absolutely necessary for its preservation.

When a determination of the direction of impact is desired, all broken glass must be recov- ered and submitted for analysis. Wherever possible, the exterior and interior surfaces of the glass must be indicated. When this is not immediately apparent, the presence of dirt, paint, grease, or putty may indicate the exterior surface of the glass.

Forensic Analysis of Soil The term soil has many definitions; however, for forensic purposes, soil may be thought of as any disintegrated surface material, natural or artificial, that lies on or near the earth’s surface. There- fore, forensic examination of soil not only is concerned with analysis of naturally occurring rocks,

FIGURE 4–23 Presence of black tungsten oxide on the upper filament indicates that the filament was on when it was exposed to air. The lower filament was off, but its surface was coated with a yellow/white tungsten oxide, which was vaporized from the upper (“on”) filament and condensed onto the lower filament. Courtesy New Jersey State Police.

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4 E. P. Junger, “Assessing the Unique Characteristics of Close-Proximity Soil Samples: Just How Useful Is Soil Evidence?” Journal of Forensic Sciences 41 (1996): 27.

5 W. J. Graves, “A Mineralogical Soil Classification Technique for the Forensic Scientist,” Journal of Forensic Sciences 24 (1979): 323; M. J. McVicar and W. J. Graves, “The Forensic Comparison of Soil by Automated Scanning Electron Microscopy,” Canadian Society of Forensic Science Journal 30 (1997): 241.

mineral A naturally occurring crystalline solid

minerals, vegetation, and animal matter; it also encompasses detection of such manufactured ob- jects as glass, paint chips, asphalt, brick fragments, and cinders, whose presence may impart soil with characteristics that make it unique to a particular location. When this material is collected accidentally or deliberately in a manner that associates it with a crime under investigation, it be- comes valuable physical evidence.4

The Significance of Soil Evidence The value of soil as evidence rests with its prevalence at crime scenes and its transferability be- tween the scene and the criminal. Thus, soil or dried mud found adhering to a suspect’s clothing or shoes or to an automobile, when compared to soil samples collected at the crime site, may link a suspect or object to the crime scene. As with most types of physical evidence, forensic soil analysis is comparative in nature; soil found in the possession of the suspect must be carefully collected to be compared to soil samplings from the crime scene and its vicinity.

However, one should not rule out the value of soil even if the site of the crime has not been ascertained. For instance, small amounts of soil may be found on a person or object far from the actual site of a crime. A geologist who knows the local geology may be able to use geological maps to direct police to the general vicinity where the soil was originally picked up and the crime committed.

Forensic Examination of Soil Most soils can be differentiated by their gross appearance. A side-by-side visual comparison of the color and texture of soil specimens is easy to perform and provides a sensitive property for distinguishing soils that originate from different locations. Soil is darker when it is wet; therefore, color comparisons must always be made when all the samples are dried under identical labora- tory conditions. It is estimated that there are nearly 1,100 distinguishable soil colors; hence, color offers a logical first step in a forensic soil comparison.

Low-power microscopic examination of soil reveals the presence of plant and animal materials as well as of artificial debris. Further high-power microscopic examination helps char- acterize minerals and rocks in earth materials. Although this approach to forensic soil identifica- tion requires the expertise of an investigator trained in geology, it can provide the most varied and significant points of comparison between soil samples. Only by carefully examining and com- paring the minerals and rocks naturally present in soil can one take advantage of the large num- ber of variations between soils and thus add to the evidential value of a positive comparison.5

A mineral is a naturally occurring crystal, and like any other crystal, its physical proper- ties—for example, color, geometric shape, density, and refractive index or birefringence—are useful for identification. More than 2,200 minerals exist; however, most are so rare that foren- sic geologists usually encounter only about 20 of the more common ones. Rocks are composed of a combination of minerals and therefore exist in thousands of varieties on the earth’s sur- face. They are usually identified by characterizing their mineral content and grain size (see Figure 4–24).

Considering the vast variety of minerals and rocks and the possible presence of artificial debris in soil, the forensic geologist is presented with many points of comparison between two or more spec- imens. The number of comparative points and their frequency of occurrence must be considered before concluding similarity between specimens and judging the probability of common origin.

Rocks and minerals not only are present in earth materials but also are used to manufacture a wide variety of industrial and commercial products. For example, the tools and garments of an in- dividual suspected of breaking into a safe often contain traces of safe insulation. Safe insulation may be made from a wide combination of mineral mixtures that provide significant points of iden- tification. Similarly, building materials such as brick, plaster, and concrete blocks are combinations of minerals and rocks that can easily be recognized and compared microscopically to similar min- erals found on the breaking-and-entering suspect.

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Variations in Soil The ultimate forensic value of soil evidence depends on its variation at the crime scene. If, for example, soil is indistinguishable for miles surrounding the location of a crime, it will have limited value in associating soil found on the suspect with that particular site. Significant con- clusions relating a suspect to a particular location through a soil comparison may be made when variations in soil composition occur every 10–100 yards from the crime site. However, even when such variations do exist, the forensic geologist usually cannot individualize soil to any one location unless an unusual combination of rare minerals, rocks, or artificial debris can be located.

No statistically valid forensic studies have examined the variability of soil evidence. A study conducted in southern Ontario, Canada, seems to indicate that soil in that part of Canada shows extensive diversity. It estimated a probability of less than 1 in 50 of finding two soils that are indistinguishable in both color and mineral properties but originate in two differ- ent locations separated by a distance of 1,000 feet. Based on these preliminary results, similar diversity may be expected in the northern United States, Canada, northern Europe, and eastern Europe. However, such probability values can only generally indicate the variation of soil within these geographical areas. Each crime scene must be evaluated separately to establish its own soil variation probabilities.

Collection and Preservation of Soil Evidence When gathering soil specimens, the evidence collector must give primary consideration to estab- lishing the variation of soil at the crime-scene area. For this reason, standard/reference soils should be collected at various intervals within a 100-yard radius of the crime scene, as well as at

FIGURE 4–24 A mineral viewed under a microscope. Courtesy of Chris Palenik, Ph.D., Microtrace LLC, Elgin, IL.

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> > > > > > > > > > > > > > > > > Soil: The Silent Witness

Alice Redmond was reported missing by her hus- band on a Monday night in 1983. Police learned that she had been seen with a co-worker, Mark Miller, after work that evening. When police ques- tioned Miller, he stated that the two just “drove around” after work and then she dropped him off at home. Despite his statement, Miller was the prime suspect because he had a criminal record for burglary and theft.

Alice’s car was recovered in town the following morning. The wheel wells were thickly coated in mud, which investigators hoped might provide a good lead. These hopes were dampened when police learned that Alice and her husband had at- tended a motorcycle race on Sunday, where her car was driven through deep mud.

After careful scrutiny, analysts found two col- ors of soil on the undercarriage of Alice’s car. The thickest soil was brown; on top of the brown layer was a reddish soil that looked unlike anything in the county. Investigators hoped the reddish soil, which had to have been deposited sometime af- ter the Sunday night motorcycle event and be- fore the vehicle was discovered on Tuesday morning, could link the vehicle to the location of Alice Redmond.

An interview with Mark Miller’s sister provided a break in the case. She told police that Mark had visited her on Monday evening. During that visit, he confessed that he had driven Alice in her car across

the Alabama state line into Georgia, killed her, and buried her in a remote location. Now that investi- gators had a better idea where to look for Alice, forensic analysts took soil samples that would prove or disprove Miller’s sister’s story.

Each field sample was dried and compared for color and texture by eye and stereomicroscopy to the reddish-colored soil gathered from the car. Next, soils that compared to the car were passed through a series of mesh filters, each of a finer gauge than the last. In this way, the components of the soil samples were physically separated by size. Finally, each fraction was analyzed and compared for mineral composition with the aid of a polarizing light microscope.

Only samples collected from areas across the Alabama state line near the suspected dump site were consistent with the topmost reddish soil re- covered from Alice’s car. This finding supported Miller’s sister’s story and was instrumental in Mark Miller’s being charged with murder and kidnap- ping. After pleading guilty, the defendant led the authorities to where he had buried the body. The burial site was within a half mile of the location where forensic analysts had collected a soil sam- ple consistent with the soil removed from Alice’s vehicle.

Source: T. J. Hopen, “The Value of Soil Evidence,” in M. M. Houck, ed., Trace Evidence Analysis: More Cases in Mute Wit- nesses (Burlington, Mass.: Elsevier Academic Press, 2004), pp. 105–22.

the site of the crime, for comparison to the questioned soil. Soil specimens also should be collected at all possible alibi locations that the suspect may claim.

All specimens gathered should be representative of the soil that was removed by the suspect. In most cases, only the top layer of soil is picked up during the commission of a crime. Thus, standard/reference specimens must be removed from the surface without digging too deeply into the unrepresentative subsurface layers. Approximately a tablespoon or two of soil is all the labo- ratory needs for a thorough comparative analysis. All specimens collected should be packaged in individual containers, such as plastic vials. Each vial should be marked to indicate the location at which the sampling was made.

Soil found on a suspect must be carefully preserved for analysis. If it is found adhering to an object, as in the case of soil on a shoe, the investigator must not remove it. Instead, each ob- ject should be individually wrapped in paper, with the soil intact, and transmitted to the labora- tory. Similarly, loose soil adhering to garments should not be removed; these items should be carefully and individually wrapped in paper bags and sent to the laboratory for analysis. Care must be taken that particles that may accidentally fall off the garment during transportation will remain in the paper bag.

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The forensic scientist must constantly determine the properties that impart distinguishing characteristics to matter, giving it a unique identity. Physical properties such as weight, volume, color, boiling point, and melting point describe a substance without reference to any other substance. A chemical property describes the behavior of a substance when it reacts or com- bines with another substance. Scientists throughout the world use the metric system of measurement. The metric system has basic units of measurement for length, mass, and volume: the meter, gram, and liter, respectively. Temperature is a measure of heat intensity, or the amount of heat in a substance. In sci- ence, the most commonly used temperature scale is the Celsius scale. This scale is derived by assigning the freezing point of water a value of 0°C and its boiling point a value of 100°C.

To compare glass fragments, a forensic scientist evaluates two important physical properties: density and refractive in- dex. Density is defined as the mass per unit volume. Refractive index is the ratio of the velocity of light in a vacuum to that in the medium under examination. Crystalline solids have defi- nite geometric forms because of the orderly arrangement of their atoms. These solids refract a beam of light in two differ- ent light-ray components. This results in double refraction. Birefringence is the numerical difference between these two refractive indices. Not all solids are crystalline in nature. For example, glass has a random arrangement of atoms to form an amorphous or noncrystalline solid.

The flotation and immersion methods are best used to determine a glass fragment’s density and refractive index, re- spectively. In the flotation method, a glass particle is im- mersed in a liquid. The density of the liquid is carefully adjusted by the addition of small amounts of an appropriate liquid until the glass chip remains suspended in the liquid medium. At this point, the glass will have the same density as the liquid medium and can be compared to other relevant pieces of glass. The immersion method involves immersing a glass particle in a liquid medium whose refractive index is var- ied until it is equal to that of the glass particle. At this point, known as the match point, minimum contrast between liquid and particle is observed.

By analyzing the radial and concentric fracture patterns in glass, the forensic scientist can determine the direction of im- pact. This can be accomplished by applying the 3R rule: Radial cracks form a Right angle on the Reverse side of the force.

The value of soil as evidence rests with its prevalence at crime scenes and its transferability between the scene and the criminal. Most soils can be differentiated by their gross appearance. A side-by-side visual comparison of the color and texture of soil specimens is easy to perform and provides a sensitive property for distinguishing soils that originate from different locations. In many forensic laboratories, forensic geologists characterize and compare the mineral content of soils.

> > > > > > > > > > >chapter summary

When a lump of soil is found, it should be collected and preserved intact. For example, an automobile tends to collect and build up layers of soil under the fenders, body, and so on. The impact of an automobile with another object may jar some of this soil loose. Once the suspect car has been apprehended, a comparison of the soil left at the scene with soil remaining on the auto- mobile may help establish that the car was present at the accident scene. In these situations, separate samples are collected from under all the fender and frame areas of the vehicle; care is taken to remove the soil in lump form in order to preserve the order in which the soil adhered to the car. Undoubtedly, during the normal use of an automobile, soil will be picked up from numerous locations over a period of months and years. This layering effect may impart soil with greater variation, and hence greater evidential value, than that normally associated with loose soil.

The prevalence of glass and soil in our environment makes them common types of physical evidence at crime scenes. Their proper collection and preservation by the criminal investigator will help ensure that a proper scientific examination can support investigative conclusions placing a suspect or object at the crime scene. Equally important is that glass and soil, like other types of physical evidence, when properly collected and examined, may exonerate the innocent from involvement in a crime.

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Forensic Glass Analysis: To perform a virtual forensic glass analysis, go to www.pearsoncustom .com/us/vlm/

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review questions

1. A(n) ___________ property describes the behavior of a substance without reference to any other substance.

2. A(n) ___________ property describes the behavior of a substance when it reacts or combines with another substance.

3. The ___________ system of measurement was devised by the French Academy of Science in 1791.

4. The basic units of measurement for length, mass, and volume in the metric system are the ___________, ___________, and ___________, respectively.

5. A centigram is equivalent to ___________ gram(s).

6. A milliliter is equivalent to ___________ liter(s).

7. 0.2 gram is equivalent to ___________ milligram(s).

8. One cubic centimeter (cc) is equivalent to one ___________.

9. True or False: One meter is slightly longer than a yard. ___________

10. The equivalent of 1 pound in grams is ___________.

11. True or False: A liter is slightly larger than a quart. ___________

12. ___________ is a measure of a substance’s heat intensity.

13. There are ___________ degrees Fahrenheit between the freezing and boiling points of water.

14. There are ___________ degrees Celsius between the freezing and boiling points of water.

15. The amount of matter an object contains determines its ___________.

16. The simplest type of balance for weighing is the ___________.

17. Mass per unit volume defines the property of ___________.

18. If an object is immersed in a liquid of greater density, it will (sink, float).

19. The bending of a light wave because of a change in ve- locity is called ___________.

20. The physical property of ___________ is determined by the ratio of the velocity of light in a vacuum to light’s velocity in a substance.

21. True or False: Solids having an orderly arrangement of their constituent atoms are crystalline. ___________

22. Solids that have their atoms randomly arranged are said to be ___________.

23. The crystal calcite has two indices of refraction. The dif- ference between these two values is known as ___________.

24. The process of separating light into its component col- ors or frequencies is known as ___________.

25. A hard, brittle, amorphous substance composed mainly of silicon oxides is ___________.

26. Glass that can be physically pieced together has ___________ characteristics.

27. The two most useful physical properties of glass for forensic comparisons are ___________ and ___________.

28. Comparing the relative densities of glass fragments is readily accomplished by a method known as ___________.

29. When glass is immersed in a liquid of similar refractive index, its ___________ disappears and minimum con- trast between the glass and liquid is observed.

30. The exact numerical density and refractive indices of glass can be correlated to ___________ in order to assess the evidential value of the comparison.

31. The fracture lines radiating outward from a crack in glass are known as ___________ fractures.

32. A crater-shaped hole in glass is (narrower, wider) on the side where the projectile entered the glass.

33. True or False: It is easy to determine from the size and shape of a hole in glass whether it was made by a bullet or some other projectile. ___________

34. True or False: Stress marks on the edge of a radial crack are always perpendicular to the edge of the surface on which the impact force originated. ___________

35. A fracture line (will, will not) terminate at an existing line fracture.

36. True or False: Most soils have indistinguishable color and texture. ___________

37. Naturally occurring crystals commonly found in soils are ___________.

38. True or False: The ultimate value of soil as evidence de- pends on its variation at the crime scene. ___________

39. To develop an idea of the soil variation within the crime- scene area, standard/reference soils should be collected at various intervals within a(n) ___________-yard ra- dius of the crime scene.

40. True or False: Each object collected at the crime scene that contains soil evidence must be individually wrapped in plastic, with the soil intact, and transmitted to the laboratory. ___________

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1. An accident investigator arrives at the scene of a hit-and- run collision. The driver who remained at the scene reports that the windshield or a side window of the car that struck him shattered on impact. The investigator searches the accident site and collects a large number of fragments of tempered glass. This is the only type of glass recovered from the scene. How can the glass evidence help the investigator locate the vehicle that fled the scene?

2. Indicate the order in which the bullet holes were made in the glass depicted in the accompanying figure. Explain the reason for your answer.

application and critical thinking

3. The accompanying figure depicts stress marks on the edge of a glass fracture caused by the application of force. If this is a radial fracture, from which side of the glass (left or right) was the force applied? From which

4. Criminalist Jared Heath responds to the scene of an assault on an unpaved lane in a rural neigh- borhood. Rain had fallen steadily the night be- fore, making the area quite muddy. A suspect with very muddy shoes was apprehended nearby but claimed to have picked up the mud either from his garden or from the unpaved parking lot of a local restaurant. Jared uses a spade to remove several samples of soil, each about 2 inches deep, from the immediate crime scene and places each in a separate plastic vial. He collects the muddy shoes and wraps them in plastic as well. At the labora- tory, he unpackages the soil samples and exam- ines them carefully, one at a time. He then analyzes the soil on the shoes to see if it matches the soil from the crime scene. What mistakes, if any, did Jared make in his investigation?

side was force applied if it is a concentric fracture? Explain the reason for your answers.

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(c)

(b)

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further references

Caddy, B., ed., Forensic Examination of Glass and Paint. New York: Taylor & Francis, 2001.

Bottrell, M.C., “Forensic Glass Comparison: Background Information Used in Data Interpretation,” Forensic Science Communications 11, no. 2 (2009), www.fbi.gov/hq/ lab/fsc/backissu/april2009/review/2009_04_review01.htm

Demmelmeyer, H., and J. Adam, “Forensic Investigation of Soil and Vegetable Materials,” Forensic Science Review 7 (1995): 119–42.

Koons, R. D., J. Buscaglia, M. Bottrell, and E. T. Miller, “Forensic Glass Comparisons,” in R. Saferstein, ed., Forensic Science Handbook, vol. 1, 2nd ed. Upper Saddle River, N.J.: Prentice Hall, 2002.

Murray, R. C., Evidence from the Earth: Forensic Geology and Criminal Investigation. Missoula, Mont.: Mountain Press, 2004.

Murray, R. C., and L. P. Solebello, “Forensic Examination of Soil,” in R. Saferstein, ed., Forensic Science Hand- book, vol. 1, 2nd ed. Upper Saddle River, N.J.: Prentice Hall, 2002.

Thornton, J. I., “Interpretation of Physical Aspects of Glass Evidence,” in B. Caddy, ed., Forensic Examination of Glass and Paint. New York: Taylor & Francis, 2001.

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