Criminalistics_CH3.pdf

Chapter 3 Physical Evidence KEY TERMS...

Chapter 3 Physical Evidence KEY TERMS class characteristics comparison identification individual After studying this chapter, you should be able to: characteristics Learning Objectives product rule 3.1 Review the common types of physical evidence encountered rapid DNA at crime scenes 3.2 Summarize the significance of physical evidence and the steps involved in its analysis 3.3 Explain the function of national databases available to forensic scientists  Headline News Bruce McArthur: A Mountain of Physical Evidence Over the course of a decade, gay men were vanishing off the streets of Toronto, Canada. The last in the string of unexplained disappearances was Andrew Kinsman, who went missing on January 26, 2017. As part of the investigation, police combed through his belongings for information on his whereabouts the day he went missing. On his calendar, there was just one entry—the name “Bruce.” Police were able to pull surveillance footage To Come of Kinsman getting into a red 2004 Dodge Caravan on the day he disappeared. When investigators cross-referenced those pieces of information, there was only one person named “Bruce” who owned a red 2004 Dodge Caravan. Police began to monitor Bruce McArthur, a 66-year-old landscaper from Toronto. After weeks of surveillance, officers observed a young man entering McArthur’s apartment. Fearing for the man’s safety, police decided to make entry. Once inside, they discovered the young man tied up but otherwise unharmed. It was at this time that Bruce McArthur was taken into custody on suspi- cion of murder. The subsequent search yielded a trove of physical evidence that linked McArthur to the killings of eight men with ties to Toronto’s Gay Village. A search of his van yielded blood that matched the DNA profiles of some of his victims. Police found a black duffel bag containing duct tape, a surgical glove, rope, zip ties, a black bungee cord, and syringes in McArthur’s bedroom. He shaved his victims’ heads and beards before burying them and kept hair from the men in bags. He buried the remains of his dismembered victims in planter pots at the home of a landscaping client. In the face of the “unprecedented amount of real, forensic, digital and documentary evidence” described by the prosecutor in the case, Bruce McArthur pled guilty to eight counts of murder in a Toronto courtroom on January 29, 2019. During the sentencing hearing, the prosecutor walked through each piece of physical evidence amassed by investigators, stating: “For years, members of the LGBTQ community in Toronto believed they were being targeted by a killer and they were right.” McArthur was sentenced to life in prison without the possibility of parole for his crimes.  PHySICAL EvIDENCE 63 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 history, circumstances, and problems. It is practical, however, to list items whose scientific ex- amination 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 are also included. 11. Organs and physiological fluids. Body organs and fluids are submitted for toxicology to detect the possible existence of drugs and poisons. This category includes blood to be ana- lyzed 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 object to another during the commission of a crime. A common example is the transfer of paint from one vehicle to another during an automobile collision. 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.  64 CHAPTER 3 19. Tool marks. This category includes any object suspected of containing the impression of another object that served as a tool in a crime. For example, a screwdriver or crowbar could produce tool marks by being impressed into or scraped along a surface of a wall. 20. Vehicle lights. Examination of vehicle headlights and taillights is normally conducted 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, shav- ings, 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 Mikael Karlsson/Alamy Stock Photo 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, FIGURE 3–1 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— The gun is fired at a set distance from the target and the gunpowder left for example, dynamite or TNT. Also, the identification of blood, semen, hair, or on the target is compared to powder wood would, as a matter of routine, include a determination of species origin. For stains found on a victim’s clothing. The example, did an evidential bloodstain originate from a human as opposed to a dog or density and shape of the powder stains cat? Each of these requests requires the analysis and ultimate identification of a spe- vary with the distance the gun was fired. cific 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 identification results have been established, they may be permanently recorded and used repeatedly to prove The process of determining a the identity of suspect materials. For example, to ascertain that a particular suspect powder is substance’s physical or chemical heroin, the test results on the powder must be identical to those that have been previously ob- identity. Drug analysis, species tained from a known heroin sample. Second, identification requires that the number and type of determination, and explosive tests needed to identify a substance be sufficient to exclude all other substances. This means that residue analysis are typical the examiner must devise a specific analytical scheme that will eliminate all but one substance examples of this undertaking in from consideration. Hence, if the examiner concludes that a white powder contains heroin, the a forensic setting. 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 different 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 identifica- tion. 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 substanti- ated beyond any reasonable doubt in a court of law. Comparison comparison A comparison analysis subjects a suspect specimen and a standard/reference specimen to the same The process of ascertaining tests and examinations for the ultimate purpose of determining whether they have a common origin. whether two or more objects have For example, the forensic scientist may place a suspect at a particular location by noting the simi- a common origin. larities 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  PHySICAL EvIDENCE 65 Dr. Chris Palenik/Microtrace LLC FIGURE 3–2 Side-by-side comparison of hairs. a vehicle suspected of being involved in the incident. The forensic comparison is actually a two-step procedure. First, combinations of select properties are chosen from the suspect and the standard/ reference specimen for comparison. The question of which and how many properties are selected 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 com- pleted, 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 50 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. Examples individual characteristics of this are the ridge characteristics of fingerprints, random striation markings on bullets or tool Properties of evidence that can marks, irregular and random wear patterns in tire or footwear impressions, handwriting charac- be attributed to a common source teristics, irregular edges of broken objects that can be fitted together like a jigsaw puzzle (see with an extremely high degree of certainty. 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 mathemati- cal 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 by the practical experience of the examiner. For example, the French scientist Victor Balthazard has mathematically deter- mined that the probability of two individuals having the same fingerprints is one out of 1 × 1060, or 1 followed by 60 zeros. This probability is so small as to exclude the possibility of any two 66 CHAPTER 3 Peter Diaczuk/John Jay College of Criminal Justice FIGURE 3–3 The body of a woman was found with evidence of a stablike wound in the neck. A pathologist found a knife blade tip in the wound in the neck. The knife blade tip was compared with the broken blade of a knife found in the trousers pocket of the accused. A close examination reveals the fit of the indentations on the edges and individual characteristics of stria from the sharpening procedure. Richard Saferstein, Ph.D. 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. individuals having the same fingerprints. This contention is also supported by the experience of fingerprint examiners who, after classifying millions of prints over the past hundred years, have never found any two to be exactly alike. class characteristics Properties of evidence that can be CLASS CHARACTERISTICS One disappointment awaiting the investigator unfamiliar with the lim- associated only with a group and itations of forensic science is the frequent inability of the laboratory to relate physical evidence to never with a single source. a common origin with a high degree of certainty. Evidence is said to possess class characteristics  PHySICAL EvIDENCE 67 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 sim- ilar 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 ex- ample, 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 factors that occur independently of each other, one can apply the product rule to calculate the overall frequency of product rule occurrence of the blood in a population. Multiplying together the frequen- For example, in the O. J. Simpson case, a bloodstain located at the crime scene was found to cies of independently occurring contain a number of factors that compared to O. J.’s blood: genetic markers to obtain an over- all frequency of occurrence for a genetic profile. Blood Factors Frequency A 26 percent EsD 85 percent PGM 21 22 2 percent 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 16, 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 or an identical twin. 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 evi- dence 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, criminal 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. 68 CHAPTER 3 Often, most of the evidence gathered is subjective in nature, prone to human error and bias. The extent to which cognitive biases may influence decision-making in forensic science is an im- portant question with implications for training and practice. There have been a number of studies that support the idea of susceptibility of forensic science practitioners to various types of confirma- tion bias. As a result, it has been recommended that forensic laboratories implement procedures designed to reduce access to unnecessary information, use of multiple comparison samples rather than a single suspect exemplar, and replication of results by analysts blinded to previous results. The believability of eyewitness accounts, confessions, and informant testimony can all be disputed, maligned, and subjected to severe attack and skepticism in the courtroom. Under these circum- stances, 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 63–64, 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 Dr. Chris Palenik/Microtrace LLC FIGURE 3–5 Side-by-side comparison of fibers.  PHySICAL EvIDENCE 69 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 collective 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 probability of involve- ment increases––dramatically. A classic example of this situation can be found in the evidence presented at the trial of Wayne Williams. Wayne Williams was charged with the murders of two individuals in the Atlanta, Georgia, metropolitan area; he was also linked to the murders of 10 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.” Williams’s case is discussed in more detail in Chapter 11. Before moving beyond the subject of the nature and values that contrast individual and class evidence, one major concern must be addressed. In 2009, the report entitled Strengthening Forensic Science in the United States: A Path Forward was issued by the National Research Council (NRC) of the National Academy of Sciences.1 The report addressed an overarching concern that has permeated the foundation of forensic evidence; that is, whether certain items of class or individual evidence is worthy of admission in a court of law. Putting aside concerns about the lack of a statistical basis to define probabilities to support the comparative significance of many types of physical evidence, the NRC report decries the fact that many forensic determinations involve subjective evaluations, whose correctness is not readily verifiable and whose accuracy is highly dependent on the experience and training of the examiner. While the NRC report encourages research to put forensic science on a more objective footing, this goal will be painstakingly slow. Alternatively, crime laboratories have been encouraged to implement quality assurance measures to measure the competency of their examiners; these include peer review, proficiency testing, analyst certification, and periodic external audits. Cautions and Limitations in Dealing with Physical Evidence In further evaluating the contribution of physical evidence, one cannot overlook one important reality in the courtroom: the weight or significance accorded to physical evidence is a determina- tion left entirely to the trier of fact, usually a jury of laypeople. Given the high esteem in which sci- entists 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 factor in reinforcing or overcoming lingering doubts about guilt or innocence. In fact, a num- ber of jurists have already cautioned against giving carte blanche approval to admitting scientific testimony 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 eliminated 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 ultimately 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 individual is a difficult question to answer and is often the source of heated debate and honest disagreement among forensic scientists. How many striations are necessary to individualize a mark to a single tool and no other? How many color layers individualize a paint chip to a single car? How many ridge characteristics individualize a fingerprint, and how many handwriting characteristics 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. 1 National Research Council, Strengthening Forensic Science in the United States: A Path Forward, Washington, D.C.: National Academies Press, 2009, http://books.nap.edu/openbook.php?record_id=12589&page=R1 70 CHAPTER 3 There are practical limits to the properties and characteristics the forensic scientist can select for comparison. Carried to the extreme, no two things in this world are alike in every detail. Modern analytical techniques have become so sophisticated and sensitive that the criminalist must be careful to define the limits of natural variation among materials when interpreting the data gathered from a comparative analysis. For example, we will learn in Chapter 10 that two properties, 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 within a single pane of glass. Certainly, this goes beyond the desires of a criminal- ist 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). Richard Saferstein, Ph.D. (a) Richard Saferstein, Ph.D. (b) 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×.  PHySICAL EvIDENCE 71 Distinguishing evidential variations from natural variations is not always an easy task. Learning how to use the microscope and all the other modern instruments in a crime laboratory properly is one thing; gaining the 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. 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 criminalist in a criminal investigation. Of course, a one-to-one comparison requires a suspect. Little or nothing of evidential value can be accomplished if crime-scene investigators acquire fingerprints, 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 investigators to uncover clues about who may have committed a crime. Today, the crime laboratory is on the forefront of the investigation seeking to identify perpetrators. This dramatic reversal of the role of forensic sci- ence in criminal investigation has come about through the creation of computerized databases that not only link all 50 states but also tie together police agencies throughout the world. Fingerprint Databases The premier model of all forensic database systems is the Integrated Automated Fingerprint Identification System (IAFIS), a national fingerprint and criminal history system maintained by the FBI. In 2014, the IAFIS was effectively replaced and integrated into the Next Generation Identification (NGI) system. The expanded capabilities of NGI beyond fingerprints will be dis- cussed in Chapter 7. IAFIS, which first became operational in 1999, contains fingerprints and access to corresponding criminal history information for nearly 75 million subjects (or 750 mil- lion 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 NGI system. 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 NGI system 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 the NGI system, and within minutes the search is completed against all fingerprint images in the NGI system; the examiner may receive a list of potential candidates and their cor- responding fingerprints for comparison and verification (see Figure 3–7). Many countries throughout the world have created national automated fingerprint identifica- tion systems that are comparable to the FBI’s model. For example, the United Kingdom has also recently created an integrated system that links police and justice agencies called IDENT1. Its primary capabilities include finger and palm print analysis, print search capabilities with access to international databases, verification of the identities of arrested persons, and information sharing capabilities between state, local, and federal agencies throughout England, Scotland, and Wales. IDENT1 provides the basis for future integrated technologies such as biometric or facial imaging. 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 en- acted legislation to establish a data bank containing DNA profiles of individuals convicted of fel- ony sexual offenses (and other crimes, depending on each state’s statute). CODIS creates inves- tigative leads from three indexes: the forensic, offender, and arrestee indices. The forensic index currently contains about 915,000 DNA profiles from unsolved crime-scene evidence. Based on a match, police in multiple jurisdictions can identify serial crimes, allowing coordination of 72 CHAPTER 3 Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC, www.sirchie.com 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 characteris- tics serve as a basis for comparing the latent print against file fingerprints. investigations and sharing of leads developed independently. The offender index contains the profiles of more than 13.6 million convicted individuals. The FBI has joined numerous states that collect DNA samples from those awaiting trial and will collect DNA from detained immi- grants. This information will be entered into the arrestee index database, presently at 3.4 million.2 Ultimately, the success of the CODIS program is measured by the crimes it helps to solve. To this end, CODIS has produced more than 451,000 hits assisting in more than 440,000 investigations. Constitutional issues regarding the appropriateness of collecting DNA from arrestees not convicted of any crime, but who nevertheless were the subject of a CODIS search against DNA collected from unsolved crimes, was decided in the case of Maryland v. King.3 When officers make an arrest supported by probable cause to hold for a serious offense and bring the suspect to a station to be detained in custody, taking and analyzing a cheek swab of the arrestee’s DNA is, like fingerprinting and photographing, a legitimate police booking procedure that is reasonable under the Fourth Amendment. With the Supreme Court sanctioning the collection of cheek or buccal swabs from arrestees, the necessity for the analysis of a swab as close to the time of arrest as possible becomes appar- Rapid DNA ent. The term Rapid DNA has become part of the lingo of forensic science and describes ap- A process for developing DNA proaches for rapidly obtaining a DNA profile from a buccal swab. A number of compact instru- profiles from a buccal swab in 90 ments are already commercially available and others are being developed. These allow for the minutes or less that are compatible development of a DNA profile from a buccal swab in less than 90 minutes. Experts envision that with a CODIS search. rapid DNA devices will take their place alongside fingerprinting units for the routine process- ing of arrestees. Recently, the FBI permitted profiles collected by Rapid DNA into the CODIS database (see Figure 3–8). Unfortunately, hundreds of thousands of samples are backlogged, still awaiting DNA analy- sis and entry into the offender index. Law enforcement agencies search this index against DNA 2 https://www.fbi.gov/services/laboratory/biometric-analysis/codis/ndis-statistics 3 133 S.Ct. 1236 (2013).  PHySICAL EvIDENCE 73 Buccal swab Rapid DNA DNA DNA profile CODIS or swab containing instrument profile evaluation database evidential DNA FIGURE 3–8 The process of taking genetic material recovered from a crime scene and entering that information into the CODIS database for comparison. profiles recovered from biological evidence found at unsolved crime scenes. This approach has proven to be tremendously successful in identifying perpetrators because most crimes involving biological evidence are committed by repeat offenders. Several countries throughout the world have initiated national DNA data banks. The United Kingdom’s National DNA Database, established in 1995, was the world’s first national data- base. Currently it holds more than 6 million profiles, and DNA can be taken for entry into the database from anyone arrested for an offense likely to involve a prison term. The National DNA Data Bank, housed in Ottawa, Canada, contains more than 379,000 DNA profiles from convicted individuals and has assisted in more than 54,000 cases, including more than 3,500 murders and more than 5,900 sexual assaults. Genealogy Databases An emerging use of forensic DNA profiles from crime scene samples involves searching unknown profiles through genealogy databases, like GEDmatch, to identify close relatives. These databases contain samples that are processed by commercial genealogy companies and uploaded by private citizens. The availability of commercial DNA testing kits, from companies like 23andMe and Ancestry.com, is credited with increasing the size and popularity of these genealogy databases. The primary purpose of these databases is to assist professional and amateur genealogists in identifying potential relatives, but because they contain DNA profiles from a wide cross sec- tion of the population, they have proved to be extremely useful in cases where investigators have DNA profiles but have not yet matched it to a source. Searching the databases is akin to a familial search, where a link can be established to a particular family lineage. Once a family lineage has been identified, the family tree can then be further examined to determine if there are individuals that fit the description of the potential person of interest. 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 scenes. Since the program’s inception in 1999, NIBIN partners have processed approximately 99,000 NIBIN leads and 110,000 NIBIN hits. Approximately 16 million images in the net- work include 3.3 million pieces of evidence. 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 posi- tively 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. The International Forensic Automotive Paint Data Query (PDQ) database contains chemical and color information pertaining to original automotive paints. This database, de- veloped and maintained by the Forensic Laboratory Services of the Royal Canadian Mounted  74 CHAPTER 3 Police (RCMP), contains information about make, model, year, and assembly plant on more than 21,000 samples corresponding to over 85,000 layers of paint. Contributors to the PDQ include 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 database has found its greatest utility in the investigation of hit-and-runs by pro- viding 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).4 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 3–9). Shoe print images can be entered into SICAR by either a scanner or a digital camera. This product has a comprehensive shoe sole database (Solemate) that includes more than 39,000 footwear entries providing inves- tigators with a means for linking a crime-scene footwear impression to a particular shoe manu- facturer. A second database, TreadMate, has been created to house tire tread patterns. Currently, it contains 8,500 records. Gerald Wallace Case Files a cigarette pack found in Wallace’s house and kept for 16 years in the police files, was entered into the Pennsylvania In 1975, police found Gerald Wallace’s body on his liv- State Police AFIS database. Within minutes, it hit a match. ing room couch. He had been savagely beaten, his hands That print, police say, gave investigators the identity of a bound with an electric cord. Detectives searched his ran- man who had been at the house the night of the murder. sacked house, cataloging every piece of evidence they could Police talked to him. He led them to other witnesses, who find. None of it led to the murderer. They had no witnesses. led them to the man police ultimately charged with the mur- Sixteen years after the fact, a lone fingerprint, lifted from der of Gerald Wallace. The Center City Rapist Case Files resulted in the arrest of Graves. However, his DNA profile inex- tricably identified him as Philadelphia’s notorious “Center City Fort Collins, Colorado, and Philadelphia, Pennsylvania, are sep- rapist.” This assailant attacked four women in 1997 and brutally arated by nearly 1,800 miles, but in 2001 they were tragically murdered Shannon Schieber, a Wharton School graduate stu- linked through DNA. Troy Graves left the Philadelphia area in dent, in 1998. His last known attack in Philadelphia was the 1999, joined the Air Force, and settled down with his wife in rape of an 18-year-old student in August 1999, shortly before Colorado. A frenzied string of eight sexual assaults around the he left the city. In 2002, Graves was returned to Philadelphia, Colorado University campus set off a manhunt that ultimately where he was sentenced to life in prison without parole. 4 Foster & Freeman Limited, http://www.fosterfreeman.co.uk  PHySICAL EvIDENCE 75 NIBIN Links Handgun to Suspects Case Files The Missing Persons Database contains information about missing persons that can be entered by anyone; how- After a series of armed robberies in which suspects fired ever, before a person appears as a case on NamUs, there shots, the sheriff’s office of Broward County, Florida, en- must be a verification by law enforcement prior to publica- tered the cartridge casings from the crime scenes into NIBIN. Through NIBIN, four of the armed robberies were tion in NamUs. When a new missing person is entered into linked to the same.40-caliber handgun. A short time later, NamUs, the system automatically performs cross-matching sheriff’s deputies noticed suspicious activity around a local with links to state clearinghouses, medical examiners’ and business. When they attempted to interview the suspects, the coroners’ offices, law enforcement agencies, and victim as- suspects fled in a vehicle. During the chase, the suspects at- sistance groups to check potential matches between cases. tempted to dispose of a handgun; deputies recovered the gun The Unidentified Persons Database contains in- after making the arrests. The gun was test-fired and the re- formation entered by medical examiners and coroners. sulting evidence entered into NIBIN, which indicated a pos- Unidentified persons are people who have died and sible link between this handgun and the four previous armed whose bodies have not been identified. Anyone can robberies. Firearms examiners confirmed the link through search this database using characteristics such as sex, examination of the original evidence. The suspects were ar- race, tattoos, and other distinctive body features, as well rested and charged with four prior armed robbery offenses. as dental information. However, sensitive case data is Over 600,000 individuals go missing in the United restricted and can be viewed only by select agencies. States every year. Medical examiners and coroners han- The Unclaimed Persons Database contains infor- dle approximately 4,000 unidentified human decedent mation about deceased persons who have been identi- cases, 1,000 of which remain unidentified after one year. fied by name, but for whom no next of kin or family The National Missing and Unidentified Persons member has been identified or located to claim the body System (NamUs) was created in 2007 as a national for burial or other disposition. Only medical examiners centralized repository and resource center for missing and coroners may enter cases in this database. However, persons and unidentified decedent records. NamUs is the database is searchable by the public using a missing a free online system that can be searched by medical person’s name and year of birth. examiners, coroners, law enforcement officials, and the In 2011, the NamUs database was awarded to the general public from all over the country in hopes of re- University of North Texas Health Science Center for solving these cases. NamUs comprises three databases, system management and ongoing development. all of which are open to the general public. Aztec Gold Metallic Hit and Run Case Files matched the paint recovered in the case. The color, Aztec Gold Metallic, was determined to have been used only on 1997 Ford A 53-year-old man was walking his dog in the early morning Mustangs. hours. He was struck and killed by an unknown vehicle and The results of the examination were relayed via telephone later found lying in the roadway. No witnesses were present, to the investigating detective. The investigating detective and the police had no leads regarding the suspect vehicle. quickly determined that only 11,000 1997 Ford Mustangs were A gold metallic painted plastic fragment recovered from the produced in Aztec Gold Metallic. Only two of these vehicles scene and the victim’s clothing were submitted to the were registered, and had been previously stopped, in the juris- Virginia Department of Forensic Science for analysis. diction of the offense. Ninety minutes after the make, model, The victim’s clothing was scraped, and several minute and year information was relayed to the investigator, he called gold metallic paint particles were recovered. Most of these back to say he had located a suspect vehicle. Molding from particles contained only topcoats, whereas one minute particle the vehicle and known paint samples were submitted for com- contained two primer layers and a limited amount of colorcoat. parison. Subsequent laboratory comparisons showed that the The color of the primer surface layer was similar to that typi- painted plastic piece recovered from the scene could be physi- cally associated with some Fords. Subsequent spectral searches cally fitted together with the molding, and paint recovered in the Paint Data Query (PDQ) database indicated that the paint from the victim’s clothing was consistent with paint samples most likely originated from a 1990 or newer Ford. taken from the suspect vehicle. The most discriminating aspect of this paint was the unusual-looking gold metallic topcoat color. A search of au- Source: Based on information obtained from Brenda Christy, Virginia tomotive repaint books yielded only one color that closely Department of Forensic Science. 76 CHAPTER 3 Photo courtesy of Foster & Freeman FIGURE 3–9 The crime-scene footwear print on the right is being searched against eight thousand sole patterns to determine its make and model. Chapter Summary Physical evidence is usually examined by a forensic scientist investigation. As the number of different objects linking an for identification or comparison purposes. The object of iden- individual to a crime scene increases, so does the likelihood tification is to determine the physical or chemical identity with of that individual’s involvement with the crime. Importantly, a as near absolute certainty as existing analytical techniques person may be exonerated or excluded from suspicion if phys- will permit. Identification first requires the adoption of testing ical evidence collected at a crime scene is found to be different procedures that give characteristic results for specific standard from standard/reference samples collected from that subject. materials. Once this is done, the examiner uses an appropriate A dramatic enhancement of the role of forensic science number of tests to identify a substance and exclude all other in criminal investigation has come about through the cre- substances from consideration. The identification process is ation of computerized databases. The Integrated Automated normally used in crime laboratories to identify drugs, explo- Fingerprint Identification System (IAFIS), a national finger- sives, and petroleum products. Also, evidence such as blood, print and criminal history system, is maintained by the FBI. semen, or hair is routinely identified in a crime laboratory. The FBI’s Combined DNA Index System (CODIS) enables Normally, these identifications would include a determination federal, state, and local crime laboratories to electronically ex- for species origin (such as human blood or rabbit hair). change and compare DNA profiles, thereby linking crimes to A comparative analysis has the important role of deter- each other and to convicted offenders. The National Integrated mining whether a suspect specimen and a standard/reference Ballistics Information Network (NIBIN), maintained by the specimen have a common origin. Both the standard/reference Bureau of Alcohol, Tobacco, Firearms and Explosives, allows specimen and the suspect specimen are subject to the same firearms analysts to acquire, digitize, and compare markings tests. Evidence that can be associated with a common source made by a firearm on bullets and cartridge casings recovered with an extremely high degree of probability is said to pos- from crime scenes. The International Forensic Automotive sess individual characteristics. Evidence associated only with Paint Data Query (PDQ) database contains chemical and a group is said to have class characteristics. Nevertheless, the color information pertaining to original automotive paints. high diversity of class evidence in our environment makes SICAR (shoeprint image capture and retrieval) has a compre- their comparison significant in the context of a criminal hensive shoe sole database.