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8 Fingerprints

Time & Life Pictures/Getty Images

LEARNING OBJECTIVES

After studying this chapter, you should be able to:

• Identify the common ridge characteristics of a fingerprint. • List the three major fingerprint patterns and their respective subclasses. • Distinguish visible, plastic, and latent fingerprints. • Describe the concept of an automated fingerprint identification system (AFIS). • List the techniques for developing latent fingerprints on porous and nonporous objects. • Describe the proper procedures for preserving a developed latent fingerprint.

JAMES EARL RAY: CONSPIRATOR OR LONE GUNMAN?

Since his arrest in 1968 for the assassination of Dr. Martin Luther King Jr., endless speculation has swirled around the motives and connections of James Earl Ray. Ray was a career criminal who was serving time for armed robbery when

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he escaped from the Missouri State Prison almost one year before the assassination. On April 3, 1968, Ray arrived in Memphis, Tennessee. The next day he rented a room at Bessie Brewer’s Rooming House, across the street from the Lorraine Motel, where Dr. King was staying.

At 6:00 p.m., Dr. King left his second-story motel room and stepped onto the balcony. As King turned toward his room, a shot rang out, striking the civil rights activist. Nothing could be done to revive him, and Dr. King was pronounced dead at 7:05 p.m. The assailant ran on foot from Bessie Brewer’s, stopping to leave a blanket-covered package in front of a nearby building, and then drove off in a white Mustang. The package contained a high-powered rifle equipped with a scope, a radio, some clothes, a pair of binoculars, a couple of beer cans, and a receipt for the binoculars. Almost a week after the shooting, the white Mustang was found abandoned in Atlanta, Georgia.

Fingerprints later identified as James Earl Ray’s were found in the Mustang, on the rifle, on the binoculars, and on a beer can. In 1969, Ray entered a guilty plea in return for a sentence of ninety-nine years. Although a variety of conspiracy theories surround this crime, it is an indisputable fact that a fingerprint on the rifle that killed Martin Luther King Jr. was from the hands of James Earl Ray.

History of Fingerprinting

Since the beginnings of criminal investigation, police have sought an infallible means of human identification. The first systematic attempt at personal identification was devised and introduced by a French police expert, Alphonse Bertillon, in 1883. The Bertillon system relied on a detailed description (portrait parlé) of the subject, combined with full-length and profile photographs and a system of precise body measurements known as anthropometry.

portrait parlé A verbal description of a perpetrator’s physical characteristics and dress provided by an eyewitness.

anthropometry A system of identification of individuals by measurement of parts of the body, developed by Alphonse Bertillon.

The use of anthropometry as a method of identification rested on the premise that the dimensions of the human bone system remain fixed from age 20 until death. Skeleton sizes were thought to be so extremely diverse that no two individuals could have exactly the same measurements. Bertillon recommended the routine taking of eleven measurements of the human anatomy, including height, reach, width of head, and length of the left foot.

For two decades, this system was considered the most accurate method of identification. But in the early years of the twentieth century, police began to appreciate and accept a system of identification based on the classification of finger ridge patterns known as fingerprints. Today, the fingerprint is the pillar of modern criminal identification.

EARLY USE OF FINGERPRINTS

In China fingerprints were used as far back as three thousand years ago to sign legal documents. Whether this practice was performed as a ceremonial custom or as a means of proving personal identity remains a point of conjecture; the answer is lost to history. The examples of fingerprinting in ancient history are ambiguous, and the few prints that remain did not in fact contribute to the development of fingerprinting techniques as we know them today.

Several years before Bertillon began work on his system, William Herschel, an English civil servant stationed in India, started requiring Indian citizens to sign contracts with the imprint of their right hand, which was pressed against a stamp pad for the purpose. The motives for Herschel’s requirement remain unclear: He may have envisioned fingerprinting as a means of personal identification, or he may have been adapting for his purposes the Hindu custom that a trace of bodily contact is more binding than a signature on a contract. In any case, he did not publish anything

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about his activities until after Henry Fauld, a Scottish physician working in a hospital in Japan, published his own views on the potential application of fingerprinting to personal identification.

In 1880, Fauld suggested that skin ridge patterns could be important for the identification of criminals. He told about a thief who left his fingerprint on a whitewashed wall, and how in comparing these prints with those of a suspect, he found that they were quite different. A few days later, another suspect was found whose fingerprints compared with those on the wall. When confronted with this evidence, the individual confessed to the crime.

Fauld was convinced that fingerprints furnished infallible proof of identification. He even offered to set up, at his own expense, a fingerprint bureau at Scotland Yard to test the practicality of the method. But his offer was rejected in favor of the Bertillon system. This decision was reversed less than two decades later.

EARLY CLASSIFICATION OF FINGERPRINTS

The extensive research into fingerprinting conducted by another Englishman, Francis Galton, finally made police agencies aware of its potential application. In 1892, Galton published his classic textbook Finger Prints, the first book of its kind on the subject. In Finger Prints, Galton discussed the anatomy of fingerprints and suggested methods for recording them. He also proposed assigning fingerprints one of three pattern types: loops, arches, or whorls. Most important, the book demonstrated that no two prints are identical and that an individual’s prints remain unchanged from year to year. At Galton’s insistence, the British government adopted fingerprinting as a supplement to the Bertillon system.

The next step in the development of fingerprint technology was the creation of classification systems capable of filing thousands of prints in a logical and searchable sequence. Dr. Juan Vucetich, an Argentinian police officer fascinated by Galton’s work, devised a workable concept in 1891. His classification system has been refined over the years and is still widely used today in most Spanish-speaking countries. In 1897, another classification system was proposed by an Englishman, Sir Edward Richard Henry. Four years later, Henry’s system was adopted by Scotland Yard. Today, most English-speaking countries, including the United States, use some version of Henry’s classification system to file fingerprints.

ADOPTION OF FINGERPRINTING

Early in the twentieth century, Bertillon’s measurement system began to fall into disfavor. Its results were highly susceptible to error, particularly when the measurements were taken by people who were not thoroughly trained. The method was dealt its most severe and notable setback in 1903 when a convict named Will West arrived at Fort Leavenworth prison. Startlingly, a routine check of the prison files revealed that a William West, already in the prison, could not be distinguished from the new prisoner by body measurements or even by photographs. In fact, the two men looked just like twins, and their measurements were practically the same. Subsequently, fingerprints of the prisoners clearly distinguished them.

In the United States, the first systematic and official use of fingerprints for personal identification was adopted by the New York City Civil Service Commission in 1901. The method was used for certifying all civil service applications. Several US police officials received instruction in fingerprint identification from representatives of Scotland Yard at the 1904 World’s Fair in St. Louis. After the fair and the Will West incident, fingerprinting began to be used in earnest in all major cities of the United States.

In 1924, the fingerprint records of the Bureau of Investigation and Leavenworth were merged to form the nucleus of the identification records of the new Federal Bureau of Investigation. The FBI has the largest collection of fingerprints

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in the world. By the beginning of World War I, England and practically all of Europe had also adopted fingerprinting as their primary method of identifying criminals.

Fundamental Principles of Fingerprints

Since Galton’s time, and as a result of his efforts, fingerprints have become an integral part of policing and forensic science. The principal reason for this is that fingerprints constitute a unique and unchanging means of personal identification. In fact, fingerprint analysts have formulated three basic principles of fingerprints that encompass these notions of their uniqueness, stability, and appropriateness as a means of identification.

FIRST PRINCIPLE: A FINGERPRINT IS AN INDIVIDUAL CHARACTERISTIC; NO TWO FINGERS HAVE YET BEEN FOUND TO POSSESS IDENTICAL RIDGE CHARACTERISTICS

The acceptance of fingerprint evidence by the courts has always been predicated on the assumption that no two individuals have identical fingerprints. Early fingerprint experts consistently referred to Galton’s calculation, showing the possible existence of 64 billion different fingerprints, to support this contention. Later, researchers questioned the validity of Galton’s figures and attempted to devise mathematical models to better approximate this value. However, no matter what mathematical model one refers to, the conclusions are always the same: The probability for the existence of two identical fingerprint patterns in the world’s population is extremely small.

Not only is this principle supported by theoretical calculations, but just as important, it is verified by the millions of individuals who have had their prints classified during the past 110 years—no two have ever been found to be identical. The FBI has nearly 50 million fingerprint records in its computer database and has yet to find an identical image belonging to two different people.

The individuality of a fingerprint is not determined by its general shape or pattern but by a careful study of its ridge characteristics (also known as minutiae). The identity, number, and relative location of characteristics such as those illustrated in Figure 8-1 impart individuality to a fingerprint. If two prints are to match, they must reveal characteristics that not only are identical but also have the same relative location to one another in the print. In a judicial proceeding, a point-by-point comparison must be demonstrated by an expert, using charts similar to the one shown in Figure 8-2, in order to prove the identity of an individual.

ridge characteristics (minutiae) Ridge endings, bifurcations, enclosures, and other ridge details that must match in two fingerprints to establish their common origin.

FIGURE 8-1 Fingerprint ridge characteristics.

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Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

An expert can easily compare the characteristics of two complete fingerprints; the average fingerprint has as many as 150 individual ridge characteristics. However, most prints recovered at crime scenes are partial impressions, showing only a segment of the entire print. Under these circumstances, the expert can compare only a small number of ridge characteristics from the recovered print to a known recorded print.

FIGURE 8-2 A fingerprint exhibit illustrating the matching ridge characteristics between the crime-scene print and an inked impression of one of the suspect’s fingers.

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For years, experts have debated how many ridge comparisons are necessary to identify two fingerprints as the same. Numbers that range from eight to sixteen have been suggested as being sufficient to meet the criteria of individuality. However, the difficulty in establishing such a minimum is that no comprehensive statistical study has ever determined the frequency of occurrence of different ridge characteristics and their relative locations. Until such a study is undertaken and completed, no meaningful guidelines can be established for defining the uniqueness of a fingerprint.

In 1973, after a three-year study of this question, the International Association for Identification concluded that “no valid basis exists for requiring a predetermined minimum number of friction ridge characters which must be present in two impressions in order to establish positive identification.” Hence, the final determination must be based on the experience and knowledge of the expert, with the understanding that others may profess honest differences of opinion on the uniqueness of a fingerprint when the question of minimal number of ridge characteristics is involved. In 1995, members of the international fingerprint community at a conference in Israel issued the Ne’urim Declaration, which supported the 1973 International Association for Identification resolution.

SECOND PRINCIPLE: A FINGERPRINT REMAINS UNCHANGED DURING AN INDIVIDUAL’S LIFETIME

Fingerprints are a reproduction of friction skin ridges found on the palm side of the fingers and thumbs. Similar friction skin can also be found on the surface of the palms and soles of the feet. Apparently, these skin surfaces have been designed by nature to provide our bodies with a firmer grasp and a resistance to slipping. A visual inspection of friction skin reveals a series of lines corresponding to hills (ridges) and valleys (grooves). The shape and form of the

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skin ridges are what one sees as the black lines of an inked fingerprint impression.

Actually, skin is composed of layers of cells. Those nearest the surface make up the outer portion of the skin known as the epidermis, and the inner skin is known as the dermis. A cross-section of skin (see Figure 8-3) reveals a boundary of cells separating the epidermis and dermis. The shape of this boundary, made up of dermal papillae, determines the form and pattern of the ridges on the surface of the skin. Once the dermal papillae develop in the human fetus, the ridge patterns remain unchanged throughout life, except for enlarging during growth.

Each skin ridge is populated by a single row of pores that are the openings for ducts leading from the sweat glands. Through these pores, perspiration is discharged and deposited on the surface of the skin. Once the finger touches a surface, perspiration, along with oils that may have been picked up by touching the hairy portions of the body, is transferred onto that surface, thereby leaving an impression of the finger’s ridge pattern (i.e., a fingerprint). Prints deposited in this manner are invisible to the eye and are commonly referred to as latent fingerprints.

latent fingerprint A fingerprint made by the deposit of oils and/or perspiration; it is invisible to the naked eye.

Although it is impossible to change one’s fingerprints, some criminals have tried to obscure them. If an injury reaches deeply enough into the skin and damages the dermal papillae, a permanent scar forms. However, for this to happen, such a wound would have to penetrate 1 to 2 millimeters beneath the skin’s surface. Indeed, efforts at intentionally scarring the skin can only be self-defeating, for it is totally impossible to obliterate all of the ridge characteristics on the hand, and the presence of permanent scars merely provides new characteristics for identification.

FIGURE 8-3 Cross-section of human skin.

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Perhaps the most publicized attempt at obliterating fingerprints was that of the notorious gangster John Dillinger, who tried to destroy his own fingerprints by applying a corrosive acid to them. Prints taken at the morgue after he was shot to death, when compared to fingerprints recorded at the time of a previous arrest, proved that his efforts had been fruitless (see Figure 8-4).

FIGURE 8-4 The right index finger impression of John Dillinger, before scarification on the left and afterward on the right. Comparison is proved by the fourteen matching ridge characteristics.

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Courtesy Institute of Applied Science, Youngsville, NC

THIRD PRINCIPLE: FINGERPRINTS HAVE GENERAL RIDGE PATTERNS THAT PERMIT THEM TO BE CLASSIFIED SYSTEMATICALLY

All fingerprints are divided into three classes on the basis of their general pattern: loops, whorls, and arches. Sixty to 65 percent of the population have loops, 30 to 35 percent have whorls, and about 5 percent have arches. These three classes form the basis for all ten-finger classification systems presently in use.

loop A class of fingerprints characterized by ridge lines that enter from one side of the pattern and curve around to exit from the same side of the pattern.

whorl A class of fingerprints that includes ridge patterns that are generally rounded or circular and have two deltas.

arch A class of fingerprints characterized by ridge lines that enter the print from one side and exit the other side.

A loop must have one or more ridges entering from one side of the print, recurving, and exiting from the same side. If the loop opens toward the little finger, it is called an ulnar loop; if it opens toward the thumb, it is a radial loop. The pattern area of the loop is surrounded by two diverging ridges known as type lines. The ridge point at or nearest the type-line divergence and located at or directly in front of the point of divergence is known as the delta. To many, a fingerprint delta resembles the silt formation that builds up as a river flows into the entrance of a lake—hence the analogy to the geological formation known as a delta. All loops must have one delta. The core, as the name suggests, is the approximate center of the pattern. A typical loop pattern is illustrated in Figure 8-5.

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Whorls are actually divided into four distinct groups, as shown in Figure 8-6: plain, central pocket loop, double loop, and accidental. All whorl patterns must have type lines and at least two deltas. A plain whorl and a central pocket loop have at least one ridge that makes a complete circuit. This ridge may be in the form of a spiral, oval, or any variant of a circle. If an imaginary line drawn between the two deltas contained within these two patterns touches any one of the spiral ridges, the pattern is a plain whorl. If no such ridge is touched, the pattern is a central pocket loop.

As the name implies, the double loop is made up of two loops combined in one fingerprint. Any whorl classified as an accidental either contains two or more patterns (not including the plain arch) or is a pattern not covered by other categories. Hence, an accidental may consist of a combination of a loop and a plain whorl or a loop and a tented arch.

FIGURE 8-5 Loop pattern.

FIGURE 8-6 Whorl patterns.

Arches, the least common of the three general patterns, are subdivided into two distinct groups: plain arches and tented arches, as shown in Figure 8-7. The plain arch is the simplest of all fingerprint patterns; it is formed by ridges entering from one side of the print and exiting on the opposite side. Generally, these ridges tend to rise in the center of the print, forming a wavelike pattern. The tented arch is similar to the plain arch except that instead of rising smoothly at the center, there is a sharp upthrust or spike, or the ridges meet at an angle that is less than 90 degrees. 1 Arches do not have type lines, deltas, or cores.

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FIGURE 8-7 Arch patterns.

THE ACE-V PROCESS

ACE-V is an acronym for the four-step process—analysis, comparison, evaluation, and verification—used to identify and individualize a fingerprint. The first step requires the examiner to identify any distortions associated with the friction ridges, as well as any external factors, such as surface or deposition factors or processing techniques, that may impinge on the print’s appearance.

The comparison step requires the examiner to compare the questioned print to the known print at three levels. Level 1 looks at the general ridge flow and pattern configuration. Level 2 includes locating and comparing ridge characteristics, or minutiae. Level 2 details can individualize a print. Level 3 includes the examination and location of ridge pores, breaks, creases, scars, and other permanent minutiae.

The evaluation stage requires the examination of the questioned and known prints in their totality. The final result of this stage is either individualization, elimination, or an inconclusive determination.

The final step in the process involves verification of the examiner’s result. It requires an independent examination of the questioned and known prints by a second examiner. Ultimately, a consensus between the two examiners must be arrived at before a final conclusion is drawn.

Quick Review

• Fingerprints are a reproduction of friction skin ridges found on the palm side of the fingers and thumbs. • The basic principles underlying the use of fingerprints in criminal investigations are as follows: (1) A fingerprint is an individual characteristic because no two fingers have yet been found to possess identical ridge characteristics, (2) a fingerprint remains unchanged during an individual’s lifetime, and (3) fingerprints have general ridge patterns that permit them to be systematically classified.

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• All fingerprints are divided into three classes on the basis of their general pattern: loops, whorls, and arches. • The individuality of a fingerprint is determined not by its general shape or pattern but by a careful study of its ridge characteristics. The expert must demonstrate a point-by-point comparison in order to prove the identity of an individual. • A four step process known as ACE-V (analysis, comparison, evaluation, and verification) is used to identify and individualize a fingerprint. • The final step in the process involves verification of the examiner’s conclusion by a second examiner. • When a finger touches a surface, perspiration and oils are transferred onto that surface, leaving a fingerprint. Prints deposited in this manner are invisible to the eye and are commonly referred to as latent or invisible fingerprints.

Classification of Fingerprints

The original Henry system, as adopted by Scotland Yard in 1901, converted ridge patterns on all ten fingers into a series of letters and numbers arranged in the form of a fraction. However, the system as it was originally designed could accommodate files of up to only 100,000 sets of prints. Thus, as collections grew in size, it became necessary to expand the capacity of the classification system. In the United States, the FBI, faced with the problem of filing ever-increasing numbers of prints, expanded its classification capacity by modifying the original Henry system and adding additional extensions. These modifications are collectively known as the FBI system and are used by most agencies in the United States today. Although we will not discuss all of the divisions of the FBI system, a description of just one part—the primary classification—will provide an interesting insight into the process of fingerprint classification.

The primary classification is part of the original Henry system and provides the first classification step in the FBI system. Using this classification alone, all of the fingerprint cards in the world could be divided into 1,024 groups. The first step in obtaining the primary classification is to pair up fingers, placing one finger in the numerator of a fraction, the other in the denominator. The fingers are paired in the following sequence:

The presence or absence of the whorl pattern is the basis for the determination of the primary classification. If a whorl pattern is found on any finger of the first pair, it is assigned a value of 16; on the second pair, a value of 8; on the third pair, a value of 4; on the fourth pair, a value of 2; and on the last pair, a value of 1. Any finger with an arch or loop pattern is assigned a value of 0. Approximately 25 percent of the population falls into the 1/1 category; that is, all their fingers have either loops or arches.

After values for all ten fingers are obtained in this manner, they are totaled, and 1 is added to both the numerator and denominator. The fraction thus obtained is the primary classification. For example, if the right index and right middle fingers are whorls and all the others are loops, the primary classification is

A fingerprint classification system cannot in itself unequivocally identify an individual; it merely provides the fingerprint examiner with a number of candidates, all of whom have a set of prints in the system’s file. The identification must always be made by a final visual comparison of the ridge characteristics of the suspect print and the file print; only these features can impart individuality to a fingerprint. Although ridge patterns impart class

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characteristics to the print, the type and position of ridge characteristics give the print individual character.

Quick Review

• The primary classification is the first step in classifying fingerprints under the FBI system. The presence or absence of the whorl pattern is the basis for the determination of the primary classification.

Automated Fingerprint Identification Systems

The Henry system and its subclassifications have proved to be a cumbersome system for storing, retrieving, and searching for fingerprints, particularly as fingerprint collections grow in size. Nevertheless, until the emergence of fingerprint computer technology, this manual approach was the only viable method for maintaining fingerprint collections. Since 1970, technological advances have made it possible to classify and retrieve fingerprints by computer. Automated fingerprint identification systems (AFISs) have proliferated throughout the law enforcement community.

In 1999, the FBI initiated full operation of the Integrated Automated Fingerprint Identification System (IAFIS), the largest AFIS in the United States, which links state AFIS computers with the FBI database. This system contains nearly 68 million fingerprint records. However, an AFIS can come in all sizes ranging from the FBI’s IAFIS to independent systems operated by cities, counties, and other agencies of local government (see Figure 8-8). Unfortunately, these local systems often cannot be linked to the state’s AFIS system because of differences in software configurations.

HOW AFIS WORKS

The heart of AFIS technology is the ability of a computer to scan and digitally encode fingerprints so they can be subjected to high-speed computer processing. The AFIS uses automatic scanning devices that convert the image of a fingerprint into digital minutiae that contain data about points of termination (i.e., ridge endings) and the branching of ridges into two ridges (i.e., bifurcations). The relative position and orientation of the minutiae are also recorded, allowing the computer to store each fingerprint in the form of a digitally recorded geometric pattern.

The computer’s search algorithm determines the degree of correlation between the location and relationship of the minutiae in the search print and those in the file prints. In this manner, a computer can make thousands of fingerprint comparisons in a second. For example, a set of ten fingerprints can be searched against a file of 500,000 ten-finger prints (i.e., ten-prints) in about eight-tenths of a second. During the search for a match, the computer uses a scoring system that assigns prints to each of the criteria set by an operator. When the search is complete, the computer produces a list of file prints that have the closest correlation to the search prints. All of the selected prints are then examined by a fingerprint expert, who makes the final verification of the print’s identity. Thus, the AFIS makes no final conclusions about the identity of a fingerprint; this function is left to the eyes of a trained examiner.

The speed and accuracy of ten-print processing by AFIS systems have made it possible to search a single latent crime-scene fingerprint against an entire file’s print collection. Before AFIS, police were usually restricted to comparing crime-scene fingerprints against those of known suspects. The impact of the AFIS on no-suspect cases has been dramatic. In its first year of operation, San Francisco’s AFIS computer conducted 5,514 latent fingerprint searches and achieved 1,001 identifications—a hit rate of 18 percent. Contrast this with the previous year’s success rate of 8 percent for manual latent-print searches.

FIGURE 8-8 An AFIS system designed for use by local law enforcement

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agencies.

Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

Using a single system, an AFIS computer automatically filters out imperfections in a latent print, enhances its image, and creates a graphic representation of the fingerprint’s ridge endings and bifurcations and their directions. The computer then searches file prints for a match. The image of the latent print and a matching file print are then displayed side by side on a high-resolution video monitor, as shown in Figure 8-9. The matching latent and file prints are then verified and charted by a fingerprint examiner at a video workstation.

The stereotypical booking officer rolling inked fingers onto a standard ten-print card for ultimate transmission to a database has, for the most part, been replaced with digital-capture devices (Live Scan) that eliminate ink and paper (see Figure 8-10). The Live Scan captures an image of each finger and the palms as they are lightly pressed against a glass plate. Within minutes the booking agency can enter the fingerprint record into the AFIS database and then search the database for previous records of the same individual.

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Live Scan An inkless device that captures digital images of fingerprints and palm prints and electronically transmits them to an AFIS.

CONSIDERATIONS WITH AFIS

AFIS has fundamentally changed the way criminal investigators operate, allowing them to spend less time developing suspect lists and more time investigating the suspects located by the computer. However, investigators must be cautioned against over reliance on a computer. Sometimes a latent print does not generate a hit because of the poor quality of the file print. To avoid potential problems, investigators must still fingerprint all known suspects in a case and then manually search these prints against the crime-scene prints.

FIGURE 8-9 A side-by-side comparison of a latent print against a file fingerprint is conducted in seconds, and their similarity rating (SIM) is displayed on the upper-left portion of the screen.

Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

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AFIS computers are available from several suppliers. Each system scans fingerprint images and detects and records information about minutiae (e.g., ridge endings and bifurcations); however, they do not all incorporate the same features, coordinate systems, or units of measure to record fingerprint information. These software incompatibilities often mean that, although state systems can communicate with the FBI’s IAFIS, they do not communicate with each other directly. Likewise, local and state systems frequently cannot share information with each other. Many of these technical problems will be resolved as more agencies follow transmission standards developed by the National Institute of Standards and Technology and the FBI.

FIGURE 8-10 Live Scan technology enables law enforcement personnel to print and compare a subject’s fingerprints rapidly, without inking the fingerprints.

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MorphoTrak, Inc.

Quick Review

• The fingerprint database known as AFIS converts an image of a fingerprint into digital minutiae that contain data showing ridges at their points of termination (i.e., ridge endings) and of branching into two ridges (i.e., bifurcations).

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• AFIS makes no final decisions on the identification of a fingerprint, instead leaving this function to a trained examiner. • Live Scan is an inkless device that captures digital images of fingerprints and palm prints and electronically transmits them to an AFIS.

Methods of Detecting Fingerprints

Through common usage, the term latent fingerprint has come to be associated with any fingerprint discovered at a crime scene. Sometimes, however, prints found at the scene of a crime are quite visible to the eye, and the word latent is a misnomer.

Actually, there are three kinds of crime-scene prints. Visible prints are made by fingers touching a surface after the ridges have been in contact with a colored material such as blood, paint, grease, or ink; plastic prints are ridge impressions left on a soft material such as putty, wax, soap, or dust; and latent or invisible prints are impressions caused by the transfer of body perspiration or oils from finger ridges to the surface of an object.

visible print A fingerprint made when the finger deposits a visible material such as ink, dirt, or blood onto a surface.

plastic print A fingerprint impressed in a soft surface.

LOCATING FINGERPRINTS

Locating visible or plastic prints at the crime scene normally presents little problem to the investigator because these prints are usually distinct and visible to the eye. Obviously, locating latent or invisible prints is much more difficult and requires the use of techniques that make the print visible. The investigator can choose from several methods for visualizing a latent print, and his or her choice depends on the type of surface being examined.

Hard and nonabsorbent surfaces (such as glass, mirror, tile, and painted wood) require different development procedures than do surfaces that are soft and porous (such as paper, cardboard, and cloth). Prints on the former surfaces are developed preferably by the application of a powder or by treatment with Super Glue, whereas prints on the latter generally require treatment with one or more chemicals.

Sometimes the most difficult aspect of fingerprint examination is the location of prints. Recent advances in fingerprint technology have led to the development of an ultraviolet image converter for the purpose of detecting latent fingerprints. This device, called the Reflected Ultraviolet Imaging System (RUVIS), can locate prints on most nonabsorbent surfaces without the aid of chemical or powder treatments (see Figure 8-11).

FIGURE 8-11 A Reflected Ultraviolet Imaging System allows an investigator to directly view surfaces for the presence of untreated latent fingerprints.

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RUVIS detects the print in its natural state by aiming UV light at the surface suspected of containing prints. When the UV light strikes a fingerprint, the light is reflected back to the viewer, differentiating the print from its background surface. The transmitted UV light is then converted into visible light by an image intensifier. Once the print is located in this manner, the crime-scene investigator can develop it in the most appropriate fashion (see Figure 8-12).

CASE FILES THE NIGHT STALKER

Richard Ramirez, the Night Stalker.

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Richard Ramirez committed his first murder in June 1984. His victim was a 79-year-old woman who was stabbed repeatedly and sexually assaulted, and then her throat was slashed. It was eight months before Ramirez killed again: In the spring of 1985, he began a murderous rampage that resulted in thirteen additional killings and five rapes.

Ramirez’s modus operandi was to enter a home through an open window, shoot the male residents, and savagely rape female victims. He scribed a pentagram and the words “Jack the Knife” on a wall in the home of one of his victims and was reported by another to have forced her to “swear to Satan” during the assault. His identity yet unknown, the news media dubbed him the “Night Stalker.” As the body count continued to rise, public hysteria and a media frenzy prevailed.

The break in the case came when the license plate of what seemed to be a car related to a sighting of the Night Stalker was reported to the police. The police determined from the plate number that the car had been stolen and eventually located it, abandoned in a parking lot. After processing the car for prints, police found one usable partial fingerprint.

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This fingerprint was entered into the Los Angeles Police Department’s brand-new AFIS computerized fingerprint system.

Without AFIS, it would have taken a single technician, manually searching Los Angeles’ 1.7 million print cards, sixty-seven years to come up with the perpetrator’s prints. Thanks to AFIS, it took only a few seconds to match and identify them. The Night Stalker was identified as Richard Ramirez, who had been fingerprinted following a traffic violation some years before. Police searching the home of one of his friends found the gun used to commit the murders, and jewelry belonging to his victims was found in the possession of Ramirez’s sister. Ramirez was convicted of murder and sentenced to death in 1989. He remains on death row.

DEVELOPING LATENT PRINTS

Several techniques are available to the criminalist for developing latent prints on a variety of surfaces. These range from chemical methods such as using powders and iodine fuming to the use of laser light.

FINGERPRINT POWDERS

Fingerprint powders are commercially available in a variety of compositions and colors. These powders, when applied lightly to a nonabsorbent surface with a camel’s-hair or fiberglass brush, readily adhere to perspiration residues and/or deposits of body oils left on the surface (see Figure 8-13).

Experienced examiners find that gray and black powders are adequate for most latent-print work; the examiner selects the powder that affords the best color contrast with the surface being dusted. Therefore, the gray powder, composed of an aluminum dust, is used on dark-colored surfaces. It is also applied to mirrors and metal surfaces that are polished to a mirror like finish because these surfaces photograph as black. The black powder, composed basically of black carbon or charcoal, is applied to white or light-colored surfaces.

FIGURE 8-12 Using a Reflected Ultraviolet Imaging System with the aid of a UV lamp to search for latent fingerprints.

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FIGURE 8-13 Developing a latent fingerprint on a surface by applying a fingerprint powder with a fiberglass brush.

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Other types of powders are available for developing latent prints. A magnetic-sensitive powder can be spread over a surface using a magnet in the form of a Magna Brush. A Magna Brush does not have any bristles to come into contact with the surface, so there is less chance that the print will be destroyed or damaged. The magnet-sensitive powder comes in black and gray and is especially useful on such items as finished leather and rough plastics, on which the texture of the surface tends to hold particles of ordinary powder. Fluorescent powders are also used to develop latent fingerprints. These powders fluoresce under ultraviolet light. By photographing the fluorescence pattern of the developing print under UV light, it is possible to see the print clearly in situations in which the color of the surface might otherwise obscure the print.

IODINE FUMING

Of the several chemical methods used for visualizing latent prints, iodine fuming is the oldest. Iodine is a solid crystal that, when heated, converts into a vapor without passing through a liquid phase; such a transformation is called sublimation. Most often, the suspect material is placed in an enclosed cabinet along with iodine crystals (see Figure 8-14). As the crystals are heated, the resultant vapors fill the chamber and combine with constituents of the latent print to make it visible.

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iodine fuming A technique for visualizing latent fingerprints by exposing them to iodine vapors.

sublimation A physical change from a solid directly into a gaseous state.

FIGURE 8-14 A heated fuming cabinet.

Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com

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CASE FILES THE MAYFIELD AFFAIR

On March 11, 2004, a series of ten explosions at four sites occurred on commuter trains traveling to or near the Atocha train station in Madrid, Spain. The death toll from these explosions was nearly 200, with more than 1,500 injured. On the day of the attack, a plastic bag was found in a van previously reported as stolen. The bag contained copper detonators like those used in the train bombs.

On March 17, the FBI received electronic images of latent fingerprints that were recovered from the plastic bag, and a search was initiated on the FBI’s IAFIS. A senior fingerprint examiner encoded seven minutiae points from the high-resolution image of one suspect latent fingerprint and initiated an IAFIS search, eventually matching the print to Brandon Mayfield. Mayfield’s prints were in the FBI’s central database because they had been taken when he joined the military, where he served for eight years before being honorably discharged as a second lieutenant.

After a visual comparison of the suspect print and file prints, the examiner concluded a “100 percent match.” The identification was verified by a retired FBI fingerprint examiner with more than thirty years of experience who was working under contract with the bureau, as well as by a court-appointed independent fingerprint examiner (see the photos).

Mayfield, age 37, a Muslim convert, was arrested on May 6 on a material witness warrant. The US Attorney’s Office came up with a list of Mayfield’s potential ties to Muslim terrorists, which they included in the affidavit they presented to the federal judge who ordered his arrest and detention. The document also said that, although no travel records were found for Mayfield, “It is believed that Mayfield may have traveled under a false or fictitious name.” On May 24, Spanish investigators linked the print from the plastic bag to an Algerian national, and Mayfield’s case was thrown out. The FBI issued him a highly unusual official apology, and his ordeal became a stunning embarrassment to the US government.

(a) A questioned print recovered in connection with the Madrid bombing investigation. (b) A file print of Brandon Mayfield.

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The Mayfield incident has been the subject of an investigation by the Office of the Inspector General (OIG), US Department of Justice (www.usdoj.gov/oig/special/s0601/final.pdf). The OIG investigation concluded that a “series of systemic issues” in the FBI Laboratory contributed to the Mayfield misidentification. The report noted that the FBI had since made significant procedural modifications to help prevent similar errors in the future, and it strongly supported the FBI’s decision to develop more objective standards for fingerprint identification. An internal review of the FBI Latent Print Unit conducted in the aftermath of the Mayfield affair has resulted in the implementation of revisions in training as well as in the decision-making process for determining the comparative value of a latent print, along with

more stringent verification policies and procedures.2

The impact of the Mayfield affair on fingerprint technology as currently practiced and the weight courts will assign to fingerprint matches in the future remain open questions.

Unfortunately, iodine prints are not permanent and begin to fade once the fuming process is stopped. Therefore, the examiner must photograph the prints immediately upon development in order to retain a permanent record. Alternatively, iodine-developed prints can be fixed by spraying them with a 1 percent solution of starch in water. The print then turns blue and lasts for several weeks to several months.

The reasons latent prints are visualized by iodine vapors are not yet fully understood. Many believe that the iodine fumes combine with fatty oils; however, there is also convincing evidence that the iodine may actually interact with residual water left on a print from perspiration. 3

NINHYDRIN

Another chemical used for visualizing latent prints is ninhydrin. The development of latent prints with ninhydrin results from its chemical reaction with amino acids present in trace amounts in perspiration, creating a purple-blue

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color. A ninhydrin (triketohydrindene hydrate) solution is commonly sprayed onto a porous surface from an aerosol can. The solution is prepared by mixing the ninhydrin powder with a suitable solvent, such as acetone or ethyl alcohol; a 0.6 percent solution appears to be effective for most applications.

ninhydrin A chemical reagent used to develop latent fingerprints on porous materials by reacting with the amino acids in perspiration.

Generally, prints begin to appear within an hour or two after ninhydrin application; however, weaker prints may be visualized after 24 to 48 hours. The development can be hastened if the treated specimen is heated in an oven or on a hot plate at a temperature of 80°C to 100°C. The ninhydrin method has developed latent prints on old paper after as long as fifteen years.

PHYSICAL DEVELOPER

Physical Developer is a third chemical mixture used for visualizing latent prints. Physical Developer is a silver nitrate–based liquid reagent. This method has gained wide acceptance by fingerprint examiners, who have found it effective for visualizing latent prints that remain undetected by the previously described methods. Also, this technique is very effective for developing latent fingerprints on porous articles that may have been wet at one time.

Physical Developer A silver nitrate–based reagent formulated to develop latent fingerprints on porous surfaces.

For most fingerprint examiners, the chemical method of choice is ninhydrin. Its extreme sensitivity and ease of application have all but eliminated the use of iodine for latent-print visualization. However, when ninhydrin fails, development with Physical Developer may provide identifiable results. Application of Physical Developer washes away any traces of proteins from an object’s surface; hence, if one wishes to use all of the previously mentioned chemical development methods on the same surface, it is necessary to first fume with iodine, follow this treatment with ninhydrin, and then apply Physical Developer to the object.

SUPER GLUE FUMING

In the past, chemical treatment for fingerprint development was reserved for porous surfaces such as paper and cardboard. However, since 1982, a chemical technique known as Super Glue fuming has gained wide popularity for developing latent prints on nonporous surfaces such as metals, electrical tape, leather, and plastic bags (see Figure 8-15).

Super Glue fuming A technique for visualizing latent fingerprints on nonporous surfaces by exposing them to cyanoacrylate vapors; named for the commercial product Super Glue.

Super Glue is approximately 98 to 99 percent cyanoacrylate ester, a chemical that interacts with and visualizes a latent fingerprint. Cyanoacrylate ester fumes can be created when Super Glue is placed on absorbent cotton treated with sodium hydroxide. The fumes can also be created by heating the glue. The fumes and the evidential object are contained within an enclosed chamber for up to six hours. Development occurs when fumes from the glue adhere to the latent print, usually producing a white-appearing latent print. Interestingly, small enclosed areas, such as the interior of an automobile, have been successfully processed for latent prints with fumes from Super Glue.

FIGURE 8-15 Super Glue fuming a nonporous metallic surface in the search for latent fingerprints.

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FIGURE 8-16 (a) A handheld fuming wand uses disposable cartridges containing cyanoacrylate. The wand is used to develop prints at the crime scene and (b) in the laboratory.

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Through the use of a small handheld wand, cyanoacrylate fuming is now easily done at a crime scene or in a laboratory setting. The wand heats a small cartridge containing cyanoacrylate. Once heated, the cyanoacrylate vaporizes, allowing the operator to direct the fumes onto the suspect area (see Figure 8-16).

OTHER TECHNIQUES FOR VISUALIZATION

In recent years, researchers have explored a variety of new processes applicable to the visualization of latent fingerprints. However, for many years progress in this field was minimal. Fingerprint specialists traditionally relied on three chemical techniques—iodine, ninhydrin, and silver nitrate—to reveal a hidden fingerprint. Then, Super Glue fuming extended chemical development to prints deposited on nonporous surfaces.

Another hint of things to come emerged with the discovery that latent fingerprints could be visualized by exposure to laser light. This laser method took advantage of the fact that perspiration contains a variety of components that fluoresce when illuminated by the light of a laser.

fluoresce To emit visible light when exposed to light of a shorter wavelength.

The next advancement in latent-fingerprint development occurred with the discovery that fingerprints could be treated with chemicals that would induce fluorescence when exposed to laser illumination. For example, application of zinc chloride after ninhydrin treatment or application of the dye rhodamine 6G after Super Glue fuming causes fluorescence and increased the sensitivity of detection on exposure to laser illumination. The discovery of numerous chemical developers for visualizing fingerprints through fluorescence quickly followed. This knowledge set the stage for the next advance in latent-fingerprint development: the alternate light source.

With the advent of chemically induced fluorescence, lasers were no longer needed to induce fingerprints to fluoresce through perspiration residues. High-intensity light sources, or alternate light sources, have proliferated and all but replaced laser lights (see Figure 8-17). High-intensity quartz halogen or xenon-arc light sources can be focused on a suspect area through a fiberoptic cable. This light can be passed through several filters, giving the user more flexibility in selecting the wavelength of light to be aimed at the latent print. Alternatively, lightweight, portable alternate light

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sources that use light-emitting diodes (LEDs) are also commercially available (see Figure 8-18).

In most cases, these light sources have proved as effective as laser light in developing latent prints, and they are commercially available at costs significantly below those of laser illuminators. Furthermore, these light sources are portable and can be readily taken to any crime scene.

FIGURE 8-17 An alternate light source system incorporating a high-intensity light source.

Courtesy Foster & Freeman Limited, Worcestershire, UK, www.fosterfreeman.co.uk

A large number of chemical treatment processes are available to the fingerprint examiner, and the field is in a constant state of flux. Selection of an appropriate procedure is best left to technicians who have developed their skills through casework experience. Newer chemical processes include a substitute for ninhydrin called DFO (1,8-diazafluoren- 9-one). This chemical visualizes latent prints on porous materials when exposed to an alternate light source. DFO has been shown to develop two and a half times more latent prints on paper than ninhydrin. 1,2-indanedione is also

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emerging as a potential reagent for the development of latent fingerprints on porous surfaces. 1,2-indanedione gives both good initial color and strong fluorescence when it reacts with amino acids derived from prints, and thus it has the potential to provide in one process what ninhydrin and DFO can do in two steps. Dye combinations known as RAM, RAY, and MRM 10, when used in conjunction with Super Glue fuming, have been effective in visualizing latent fingerprints by fluorescence. A number of chemical formulas useful for latent-print development are listed in Appendix III.

FIGURE 8-18 A lightweight handheld alternate light source that uses LEDs.

Courtesy Foster & Freeman Limited, Worcestershire, UK, www.fosterfreeman.co.uk

CLOSER ANALYSIS FLUORESCENCE

Fluorescence occurs when a substance absorbs light and reemits the light in wavelengths longer than that of the illuminating source. Importantly, substances that emit light or fluoresce are more readily seen either with the naked eye

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or through photography than are non-light-emitting materials. The high sensitivity of fluorescence serves as the underlying principle of many of the new chemical techniques used to visualize latent fingerprints.

A schematic depicting latent-print detection with the aid of a laser.

Courtesy Federal Bureau of Investigation, Washington, DC

The earliest use of fluorescence to visualize fingerprints came with the direct illumination of a fingerprint with argon-ion lasers. This laser type was chosen because its blue-green light induced some of the perspiration components of a fingerprint to fluoresce (see figure). The major drawback of this approach is that the perspiration components of a fingerprint are often present in quantities too minute to observe even with the aid of fluorescence.

The fingerprint examiner, wearing safety goggles containing optical filters, visually examines the specimen being exposed to the laser light. The filters absorb the laser light and permit the wavelengths at which latent-print residues fluoresce to pass through to the eyes of the wearer. The filter also protects the operator against eye damage from scattered or reflected laser light. Likewise, latent-print residue producing sufficient fluorescence can be photographed by placing this same filter across the lens of the camera. Examination of specimens and photography of the fluorescing latent prints are carried out in a darkened room.

Studies have demonstrated that common fingerprint-developing agents do not interfere with DNA-testing methods

used for characterizing bloodstains.5 Nonetheless, in cases involving items with material adhering to their surfaces and/or items that will require further laboratory examinations, fingerprint processing should not be performed at the crime scene. Rather, the items should be submitted to the laboratory, where they can be processed for fingerprints in

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conjunction with other necessary examinations.

Quick Review

• Visible prints are made when fingers touch a surface after the ridges have been in contact with a colored material such as blood, paint, grease, or ink. • Plastic prints are ridge impressions left on a soft material, such as putty, wax, soap, or dust. • Latent prints deposited on hard and nonabsorbent surfaces (such as glass, a mirror, tile, and painted wood) are usually developed by the application of a powder, whereas prints on porous surfaces (such as papers and cardboard) generally require treatment with a chemical. • Examiners use various chemical methods to visualize latent prints, such as iodine fuming, ninhydrin, and Physical Developer. • Super Glue fuming develops latent prints on nonporous surfaces. • Latent fingerprints can also be treated with chemicals that induce fluorescence when exposed to a high-intensity light or an alternate light source.

Preservation of Developed Prints

Once the latent print has been visualized, it must be permanently preserved for future comparison and possible use in court as evidence. A photograph must be taken before any further attempts at preservation. Any camera equipped with a close-up lens will do; however, many investigators prefer to use a camera specially designed for fingerprint photography. Such a camera comes equipped with a fixed focus to take photographs on a 1:1 scale when the camera’s open eye is held exactly flush against the print’s surface (see Figure 8-19). In addition, photographs must be taken to provide an overall view of the print’s location with respect to other evidential items at the crime scene.

Once photographs have been secured, one of two procedures is followed. If the object is small enough to be transported without destroying the print, it should be preserved in its entirety. The print should be covered with cellophane so it will be protected from damage. On the other hand, prints on large immovable objects that have been developed with a powder can best be preserved by “lifting.” The most popular type of lifter is a broad adhesive tape similar to Scotch tape. Fingerprint powder is applied to the print, and the surface containing the print is covered with the adhesive side of the tape. When the tape is pulled up, the powder is transferred to the tape. Then the tape is placed on a properly labeled card that provides a good background contrast with the powder.

A variation of this procedure is the use of an adhesive-backed clear plastic sheet attached to a colored cardboard backing. Before it is applied to the print, a celluloid separator is peeled from the plastic sheet to expose the adhesive lifting surface. The tape is then pressed evenly and firmly over the powdered print and pulled up (see Figure 8-20). The sheet containing the adhering powder is then pressed against the cardboard backing to provide a permanent record of the fingerprint.

FIGURE 8-19 A camera fitted with an adapter designed to give an approximate 1:1 photograph of a fingerprint.

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FIGURE 8-20 “Lifting” a fingerprint.

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Digital Imaging for Fingerprint Enhancement

When fingerprints are lifted from a crime scene, they are not usually in perfect condition, which can make analysis difficult. As computers have advanced technology in most fields, fingerprint imaging has not been left behind. With the help of digital imaging software, fingerprints can now be enhanced for the most accurate and comprehensive analysis.

Digital imaging is the process by which a picture is converted into a digital file. The image produced from this digital file is composed of numerous square electronic dots called pixels. Images composed of only black and white elements are referred to as grayscale images. Each pixel is assigned a number according to its intensity, ranging from 0 (black) to 255 (white), and together these shaded pixels create an image. Once an image is digitally stored, it can be manipulated by computer software that changes the numerical value of each pixel, thus altering the image as directed by the user. The resolution is the degree of detail that can be seen in an image. It is defined in terms of dimensions, such as 800 × 600 pixels. The larger the numbers, the more closely the digital image resembles the real-world image.

digital imaging A process through which a picture is converted into a series of square electronic dots known as pixels.

pixel A square electronic dot that is used to compose a digital image.

The input of pictures into a digital imaging system is usually done through the use of scanners, digital cameras, and video cameras. After the picture is converted into a digital image, several methods can be employed to enhance it. The overall brightness of an image, as well as the contrast between the image and the background, can be adjusted through

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contrast-enhancement methods. One approach used to enhance an image is spatial filtering, in which several types of filters produce various effects. A low-pass filter is used to eliminate harsh edges by reducing the intensity difference between pixels. A high-pass filter operates by modifying a pixel’s numerical value to exaggerate the difference between its intensity and that of its neighbor. The resulting effect increases the contrast of the edges, thus providing a high contrast between the elements and the background. Frequency analysis, also referred to as frequency Fourier transform (FFT), is used to identify periodic or repetitive patterns such as lines or dots that interfere with the interpretation of the image. These patterns are diminished or eliminated to enhance the appearance of the image. Interestingly, the spaces between fingerprint ridges are themselves periodic. Therefore, the fingerprint can be identified apart from its background in FFT mode and then enhanced. Likewise, if ridges from overlapping prints are positioned in different directions, their corresponding frequency information is at different locations in FFT mode. The ridges of one latent print can then be enhanced while the ridges of the other are suppressed.

FIGURE 8-21 A fingerprint being enhanced in Adobe Photoshop. In this example, on the left is the original scan of an inked fingerprint on a check. On the right is the same image after eliminating the green security background using Adobe Photoshop’s Channel Mixer.

Courtesy Imaging Forensics, Fountain Valley, CA, www.imaging-forensics.com

Color interferences can pose a problem when analyzing an image. For example, a latent fingerprint found on paper currency or a check may be difficult to analyze because of the distracting colored background. With the imaging software, the colored background can simply be removed to make the image stand out (see Figure 8-21). If the image itself is a particular color, such as a ninhydrin-developed print, the color can be isolated and enhanced to distinguish it

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from the background.

Digital imaging software also provides functions in which portions of the image can be examined individually. With a scaling and resizing tool, the user can select a part of an image and resize it for a closer look. This function operates much like a magnifying glass, helping the examiner view the fine details of an image.

An important and useful tool, especially for fingerprint identification, is the compare function. This specialized feature places two images side by side and allows the examiner to chart the common features in both images simultaneously (see Figure 8-22). The zoom function is used in conjunction with the compare tool. As the examiner viewing the image on the screen zooms in to a portion of one image, the software automatically zooms in to the second image for comparison.

Digital imaging is undoubtedly an effective tool for enhancing and analyzing images, and the benefits of digital enhancement methods are apparent when weak images are made more distinguishable. However, the tools are only as useful as the images they have to work with. If the details do not exist on the original images, the enhancement procedures are not going to work.

Quick Review

• Once a latent print has been visualized, it must be permanently preserved for future comparison and for possible use as court evidence. A photograph must be taken before any further attempts at preservation are made. • A common method for preserving a print developed with a powder is lifting the print with an adhesive tape. • Digital imaging is a process in which a picture is converted into a series of square electronic dots known as pixels. Fingerprints can be enhanced with digital imaging.

FIGURE 8-22 Current imaging software allows fingerprint analysts to prepare a fingerprint comparison chart. The fingerprint examiner can compare prints side by side and display important features that are consistent between the fingerprints. This sort of digital display can be created in about thirty to sixty minutes.

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Virtual Lab Fingerprinting

To perform a virtual fingerprinting analysis, go to www.pearsoncustom.com/us/vlm/

CHAPTER REVIEW

• Fingerprints are a reproduction of friction skin ridges found on the palm side of the fingers and thumbs. • The basic principles underlying the use of fingerprints in criminal investigations are as follows: (1) A fingerprint is an individual characteristic because no two fingers have yet been found to possess identical ridge characteristics, (2) a fingerprint remains unchanged during an individual’s lifetime, and (3) fingerprints have general ridge patterns that permit them to be systematically classified. • All fingerprints are divided into three classes on the basis of their general pattern: loops, whorls, and arches. • The individuality of a fingerprint is determined not by its general shape or pattern but by a careful study of its ridge characteristics. The expert must demonstrate a point-by-point comparison in order to prove the identity of an individual.

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• A four-step process known as ACE-V (analysis, comparison, evaluation, and verification) is used to identify and individualize a fingerprint. • The final step in the process involves verification of the examiner’s conclusion by a second examiner.

• When a finger touches a surface, perspiration and oils are transferred onto that surface, leaving a fingerprint. Prints deposited in this manner are invisible to the eye and are commonly referred to as latent or invisible fingerprints. • The primary classification is the first step in classifying fingerprints under the FBI system. The presence or absence of the whorl pattern is the basis for the determination of the primary classification. • The fingerprint database known as AFIS converts an image of a fingerprint into digital minutiae that contain data showing ridges at their points of termination (i.e., ridge endings) and of branching into two ridges (i.e., bifurcations). • AFIS makes no final decisions on the identification of a fingerprint, instead leaving this function to a trained examiner. • Live Scan is an inkless device that captures digital images of fingerprints and palm prints and electronically transmits them to an AFIS. • Visible prints are made when fingers touch a surface after the ridges have been in contact with a colored material such as blood, paint, grease, or ink. • Plastic prints are ridge impressions left on a soft material, such as putty, wax, soap, or dust. • Latent prints deposited on hard and nonabsorbent surfaces (such as glass, a mirror, tile, and painted wood) are usually developed by the application of a powder, whereas prints on porous surfaces (such as papers and cardboard) generally require treatment with a chemical. • Examiners use various chemical methods to visualize latent prints, such as iodine fuming, ninhydrin, and Physical Developer. • Super Glue fuming develops latent prints on nonporous surfaces. • Latent fingerprints can also be treated with chemicals that induce fluorescence when exposed to a high-intensity light or an alternate light source. • Once a latent print has been visualized, it must be permanently preserved for future comparison and for possible use as court evidence. A photograph must be taken before any further attempts at preservation are made. • A common method for preserving a print developed with a powder is lifting the print with an adhesive tape. • Digital imaging is a process in which a picture is converted into a series of square electronic dots known as pixels. Fingerprints can be enhanced with digital imaging.

KEY TERMS

anthropometry 162

arch 167

digital imaging 182

fluoresce 178

iodine fuming 176

latent fingerprint 166

Live Scan 171

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loop 167

ninhydrin 177

Physical Developer 177

pixel 182

plastic print 173

portrait parle 162

ridge characteristics (minutiae) 164

sublimation 177

Super Glue fuming 177

visible print 173

whorl 167

REVIEW QUESTIONS

1.

The first systematic attempt at personal identification was devised and introduced by ______________.

2.

A system of identification relying on precise body measurements is known as ________________.

3.

The first book written on the subject of fingerprints, called Finger Prints, was written in 1892 by ________________ and discussed the anatomy of fingerprints and suggested methods for recording them.

4.

The fingerprint classification system used in most English-speaking countries was devised by ________________.

5.

True or False: The first systematic and official use of fingerprints for personal identification in the United States was adopted by the New York City Civil Service Commission. ________________

6.

The ________________ has the largest collection of fingerprints in the world.

7.

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Galton calculated that approximately ________________ different fingerprints could exist, and current figures are similarly high.

8.

________________ True or False: The individuality of a fingerprint is determined by its pattern. ________________

9.

A point-by-point comparison of a fingerprint’s ________________ must be demonstrated in order to prove identity.

10.

________________ are a reproduction of friction skin ridges.

11.

The form and pattern of skin ridges are determined by the skin layer called the ________________.

12.

Fingerprints deposited on a surface when oils and sweat are excreted from pores on the friction ridges are called ________________ fingerprints.

13.

A permanent scar forms in the skin only when an injury damages the ________________.

14.

True or False: Fingerprints cannot be changed during a person’s lifetime. ________________

15.

The three general patterns into which fingerprints are

16.

The most common fingerprint pattern is the

17.

Approximately 5 percent of the population has the ________________ fingerprint pattern.

18.

A loop pattern that opens toward the thumb is known as a(n) ________________ loop.

19.

The pattern area of the loop is enclosed by two diverging ridges known as ________________.

20.

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The ridge point nearest the type-line divergence is known as the ________________.

21.

True or False: All loops must have two deltas.

22.

The approximate center of a loop pattern is called the

23.

A whorl pattern has ________________ deltas and at least ________________ ridge(s) that make a complete circuit.

24.

If an imaginary line drawn between the two deltas of a whorl pattern touches any of the spiral ridges, the pattern is classified as a(n) ________________.

25.

The simplest of all fingerprint patterns is the

26.

True or False: Arches have type lines, deltas, and cores.

27.

The presence or absence of the ________________ pattern is used as a basis for determining the primary classification in the Henry system.

28.

________________ The largest category (25 percent) of the population has a ________________ primary classification, meaning all their fingers have loops or arches.

29.

True or False: A fingerprint classification system can unequivocally identify an individual. ________________

30.

True or False: Computerized fingerprint search systems match prints by comparing the positions of bifurcations and ridge endings. ________________

31.

By determining the degree of correlation between the location and relationship of the ________________ for both the search and file fingerprints, a computer can make thousands of fingerprint comparisons in a second.

32.

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________________ The digital-capture device called ________________ has eliminated ink and paperforthe collection of file fingerprints.

33.

________________ A fingerprint left by a person with soiled or stained fingertipsis called a(n) ________________.

34.

________________ fingerprints are impressions left on a soft material.

35.

Fingerprints on hard and nonabsorbent surfaces are best developed by the application of a(n) ________________.

36.

Fingerprints on porous surfaces are best developed with ________________ treatment.

37.

________________ vapors chemically combine with fatty oils or residual water to visualize a fingerprint.

38.

________________ The chemical ________________ visualizes fingerprints by its reaction with amino acids.

39.

________________ Chemical treatment with ________________ visualizes fingerprints on porous articles that may have been wet at one time.

40.

True or False: A latent fingerprint is first treated with Physical Developer followed by ninhydrin. ________________

41.

A chemical technique known as ________________ is used to develop latent prints on nonporous surfaces such as metal and plastic.

42.

________________ occurs when a substance absorbs light and reemits the light in wavelengths longer than the illuminating source.

43.

________________ High-intensity light sources, known as ________________, are effective in developing latent fingerprints.

44.

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Once a fingerprint has been visualized, it must first be preserved by ________________.

45.

Fingerprints on large immovable objects that have been developed with a powder can best be preserved by ________________ with a broad adhesive tape similar to Scotch tape.

APPLICATION AND CRITICAL THINKING

1.

Classify each of the following prints as loop, whorl, or arch.

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2.

Following is a description of the types of prints from the fingers of a criminal suspect. Using the FBI system, determine the primary classification of this individual.

Finger Right Hand Left Hand

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Finger Right Hand Left Hand

Thumb Whorl Whorl

Index Loop Whorl

Middle Whorl Arch

Ring Whorl Whorl

Little Arch Whorl

3.

While searching a murder scene, you find the following items that you believe may contain latent fingerprints. Indicate whether prints on each item should be developed using fingerprint powder or chemicals.

a. A leather sofa b. A mirror c. A painted wooden knife handle d. Blood-soaked newspapers e. A revolver

4.

Criminalist Frank Mortimer is using digital imaging to enhance latent fingerprints. Indicate which features of digital imaging he would most likely use for each of the following tasks:

a. Isolating part of a print and enlarging it for closer examination b. Increasing the contrast between a print and the background surface on which it is located c. Examining two prints that overlap each other

5.

The following are fingerprint patterns of three men and a woman with criminal records for robbery. Identify the following fingerprints according to the three groups and the subgroups of fingerprints.

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6.

Count the number of bifurcations in the following prints. Choose between 9, 11, and 13.

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Number of bifurcations:

7.

At the Museum of Culture Studies, a diary that belonged to Martin Luther King Jr. has been stolen and replaced by a fake. The only evidence is a fingerprint impression left by the thief on the fake diary. The police suspect four individuals who have had previous criminal records for similar crimes. Their fingerprints already exist in the police database. KJ, Ivan, Lisa, and Charlie are the four suspects. Carefully examine the criminal’s fingerprint impression and identify the suspect fingerprint that matches the most closely with it.

Crime Scene Fingerprint

KJ

Ivan

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Lisa

Charlie

ENDNOTES

1.

A tented arch is also any pattern that resembles a loop but lacks one of the essential requirements for classification as a loop.

2.

Smrz, M. A., et al., “Review of FBI Latent Print Unit Processes and Recommendations to Improve Practices and Quality,” Journal of Forensic

Identification 56 (2006): 402-433.

3.

J. Almag, Y. Sasson, and A. Anati, “Chemical Reagents for the Development of Latent Fingerprints II: Controlled Addition of Water Vapor to

Iodine Fumes—A Solution to the Aging Problem,” Journal of Forensic Sciences 24 (1979): 431.

4.

F. G. Kendall and B. W. Rehn, “Rapid Method of Super Glue Fuming Application for the Development of Latent Fingerprints,” Journal of

Forensic Sciences 28 (1983): 777.

5.

C. Roux et al., “A Further Study to Investigate the Effect of Fingerprint Enhancement Techniques on the DNA Analysis of Bloodstains,” Journal

of Forensic Identification 49 (1999): 357; C. J. Frégeau et al., “Fingerprint Enhancement Revisited and the Effects of Blood Enhancement

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Chemicals on Subsequent Profiler Plus™ Fluorescent Short Tandem Repeat DNA Analysis of Fresh and Aged Bloody Fingerprints,” Journal of

Forensic Sciences AS (2000): 354; P. Grubwieser et al., “Systematic Study on STR Profiling on Blood and Saliva Traces after Visualization of

Fingerprints,” Journal of Forensic Sciences 48 (2003): 733.

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9 Firearms Tool Marks, and Other Impressions

Image courtesy of National Atlas

LEARNING OBJECTIVES

After studying this chapter, you should be able to:

• Describe techniques for rifling a barrel. • Recognize the class and individual characteristics of bullets and cartridge cases. • Understand the use of the comparison microscope to compare bullets and cartridge cases. • Explain the concept of the NIBIN database. • Explain the procedure for determining how far from a target a weapon was fired. • Identify the laboratory tests for determining whether an individual has fired a weapon. • Explain the forensic significance of class and individual characteristics to the comparison of tool mark, footwear, and tire impressions. • List some common field reagents used to enhance bloody footprints.

THE BELTWAY SNIPERS

During a three-week period in October 2002, ten people were killed and three others wounded as two snipers terrorized

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the region in and around the Baltimore/Washington metropolitan area. The arrest of John Allen Muhammad, 41, and Lee Boyd Malvo, 17, ended the ordeal. The semiautomatic .223-caliber rifle seized from them was ultimately linked by firearm tests to eight of the ten killings. The car that Muhammad and Malvo were driving had been specially adapted with one hole in the trunk through which a rifle barrel could protrude, so that a sniper could shoot from inside the slightly ajar trunk.

The major break in the case came when a friend of Muhammad’s called police suggesting that Muhammad and his friend Malvo were the likely snipers. Muhammad’s automobile records revealed numerous traffic stops in the Beltway area during the time of the shootings. Another break in the case came when Malvo called a priest to boast of a killing that had occurred weeks before, in Montgomery, Alabama. Investigators traced the claim to a recent liquor store holdup that left one person dead. Fortunately, the perpetrator of this crime left a latent fingerprint at the murder scene. Authorities quickly tracked the print to Malvo, a Jamaican citizen, through his fingerprints on file with the Immigration and Naturalization Service. A description of Muhammad’s car was released to the media, leading to tips from alert citizens who noticed the car parked in a rest area with both occupants asleep.

The motive for the shooting spree was believed to be a plot to extort $10 million from local and state governments. Muhammad was sentenced to death, and Malvo is currently serving life imprisonment without parole.

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