1.1 Introduction
Forensic science is simply defined as the application of science to the law or legal matters. In today’s CSI and Forensic Files world, this area of science is much more widely known to the general public. However, it is also misunderstood due to Hollywood’s resolve to complete every case within the context of a one-hour, commercials included, pseudo-real-life crime drama.
When the actual real-life judicial system needs science to resolve a question, the person who is called upon to bring science into the courtroom is often a forensic scientist. The law and science are strange bedfellows. Science is an empirical method of learning, anchored to the principles of observation and discovery as to how the natural world works. Scientific knowledge increases human understanding by developing experiments that provide the scientist with an objective answer to the question presented. Through the scientific method of study, a scientist systematically observes physical evidence and methodically records the data that support the scientific process. The law, on the other hand, starts out with at least two competing parties with markedly different views who use the courthouse as a battleground to resolve factual issues within the context of constitutional, statutory, and decisional law.
1.2 Science
The essence of any scientific study involves developing an alternative hypothesis, devising an experiment or series of experiments to test the accuracy of the hypothesis (question presented), and finally, carrying out the scientific experiment so as to yield an unbiased result. Science meets the law only to the extent that the legal system must look to science to help resolve a legal dispute. Scientists in today’s world no longer maintain the fiction that all science is equal. This inequality is often played out in courtrooms throughout the United States. The fundamental paradigm of the judicial system in America is that science is an open process, collegial in nature, unlike the legal system, which is adversarial in nature and legal strategies are developed in secret. The overriding objective of the parties in a legal dispute is to win.
With a scientist, the objective of the scientific endeavor is to reach a correct result that will withstand scrutiny from fellow scientists who can review the methodology and examine the data. Science is premised upon observable phenomena, logical deductions, and inferences that are transparent and open to scrutiny. The inherently conflicting underpinnings between science and the law frequently make forensic science controversial and the courthouse an open arena in which forensic scientists are used as pawns in the resolution of legal disputes. To complicate the legal process, each of the nonscientist parties has an interest in the outcome, be it significant sums of money, personal freedom, or even life itself in cases involving the death penalty. At the center of legal cases there sits a person who wears a long black robe to whom we refer as a judge. The judge’s job, usually with the help of a jury, is to keep the adversarial parties at bay long enough to accomplish the orderly resolution of the factual questions raised by the warring litigants using applicable law.
The logic of the legal system is further complicated for the forensic scientist because often conflicting forensic scientific evidence that is generated by the opposing parties is ultimately submitted to the review and decision of twelve citizens, known as a trial jury. Those jurors are selected on the basis of each juror not having any knowledge or understanding of forensic or real-world science other than that occasional episode of CSI or Forensic Files.
The most common question asked by the legal system of a forensic scientist is a request to provide proof of identity of an item or person, which is a component of criminalistics. This area of forensic science involves the association of an evidentiary item that is typically related to a crime. A forensic identification has two essential steps: The first step is a comparison between an unknown evidentiary item and a known item and having the forensic scientist render a judgment as to whether there is a sufficient concordance to say there is a “match.” Examples of these comparative sciences include latent prints located at a crime scene thereafter compared to the known prints of science, the law, and Forensic identification a person, and bullet(s) collected from a body at autopsy compared to test bullets fired from suspected weapons. The second part to the identification analysis should give some meaning to the concordance (match) by providing a scientific statement that would allow the trier of fact, a judge or jury, to weigh the significance of the matching association and answer a simple question for the benefit of the trier of fact: What does “match” mean?
A forensic investigation requires a skillful blend of science using both proven techniques and common sense. The ultimate effectiveness of the scientific investigation depends upon the abi lity of the forensic scientist to apply the scientific method to reach a valid, reliable, and supportable conclusion about a question in controversy. Overall, science and the law must coexist within the framework of our judicial system, although each discipline may and often does have conflicting and competing interests. Any expert who is interested in the practice of a forensic science specialty must have a clear understanding not only of the fundamental principles of science, and presumably his or her chosen field, but also of the applicable legal standards relating to that area of forensic science; they must know quite a lot about that area of the law.
1.3 The Law
Expert testimony is a common and essential component in both civil and criminal trials. Every forensic scientist who is called into court to give the results of his or her study must first be qualified as an expert witness. Courts allow expert testimony out of necessity to assist the fact finder. A witness qualifies as an expert by reason of “knowledge, skill, experience, training, or education.”
The trial judge determines if a witness is qualified as an expert and in what field of areas of science the expert may testify.
The forensic scientist may qualify as an expert on the basis of education, background, or study.
Evidence being offered by a qualified forensic expert is subject to admissibility standards for the specific scientific evidence being presented. A judge must determine admissibility of that scientific evidence. Before a judge can make that determination, the proffered scientific evidence must first pass a simple test of relevancy. Relevant evidence is defined by the Federal Rules of Evidence and most state court jurisdictions as “evidence having any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence.
Once a court determines that the proffered scientific evidence is relevant, there are two different legal standards that courts apply in determining the admissibility of evidence: the Frye general acceptance standard and the Daubert scient ific rel iabi l ity standard. The original scientific admissibility test developed in the case of Frye v. United States held that, to be admissible, scientific evidence must be “sufficiently established to have gained general Forensic dentistry acceptance in the particular field in which it belongs.”
After the development of the Frye general acceptance standard, federal and state courts attempted to apply the rule to a wide variety of scientific evidentiary issues with mixed results. Courts often struggled with the Frye standard because the inquiry did not focus on the reliability of the particular scientific evidence; instead, the Frye test focused upon the general reliability of the scientific testing as a whole and its acceptance by others in the field. Another problem was that it was difficult to identify the appropriate expert community to answer the question of general acceptance. Some courts became concerned with the correctness of the Frye standard because the standard unfairly discredited new tests and accepted scientific principles. In 1993, the Supreme Court developed a new standard for scientific evidence in Daubert v. Merrell Dow Pharmaceuticals.
In Daubert, the Supreme Court concluded that in order for scientific evidence to be admissible, it must be shown to be scientifically valid and relevant to at least one issue in the case.
The Supreme Court offered numerous factors to aid federal judges in making the determination of scientific admissibility. These factors included whether the technique has been or can be tested, whether the technique has been subjected to peer review or publication, the known or potential rate of error, whether the technique is generally accepted in the community, and whether the technique was created outside of the litigation process. The Daubert test still allows courts to consider the issues addressed in the Frye standard because the “generally accepted” prong is one of many factors—instead of the sole factor in the analysis. By replacing Frye with Daubert, the U.S. Supreme Court made the trial judge a “gatekeeper” for the admissibility of any scientific evidence.
1.4 Forensic Identification and Forensic Dentistry
The field of forensic dentistry or the more professional term, forensic odontology, is the application of dentistry to the law. Forensic dentistry now has been an integral part of the American judicial system for well over three decades. Overall, forensic dentistry includes multiple areas of scientific study, where the legal system and dentistry coincide. This specialized area of dentistry includes the gathering and interpretation of dental and related evidence within the overall field of criminalistics. Forensic dental evidence ranges from the identification of persons using dental records to the identification and analysis of bitemarks on an object such as a food item, or a bitemark on a victim compared to a suspect, or on a suspect compared to a victim, to the estimation of a person’s age based upon dental development or other characteristics.
The forensic dentist is often an expert witness in civil disputes where dental injuries are at issue or there is a question of dental malpractice. Legal science, the law, and Forensic identification liability cases relating to injuries to the teeth, mouth, or jaw may involve the expertise of a forensic dentist (odontologist). A qualified dental expert can provide opinion testimony on issues relating to the loss or damage to teeth and the effect of the loss or damage to an injured individual. For example, if a person was involved in an automobile accident or an altercation where
legal liability is in question, the forensic dentist may explain to the jury how the accident or assault caused the dental injury to occur. In criminal cases, the forensic dentist will assist the judge or jury by relating expert testimony concerning a dental identification examination or by identifying bitemarks and giving an opinion as to who may have made the bitemark.
Dental identification of a person from dental records by a qualified forensic dentist has long been established and accepted by courts as a means to prove the identity of an individual. A question as to the identification of a person may arise from a mass disaster, such as an airplane crash, natural disaster, or a situation where multiple people died in a fire and the bodies are not otherwise recognizable. Dental identifications relying on x-rays and dental records universally have been considered to be a reliable identification method and rarely has a legal challenge been raised in court. Age estimation using dental evidence is necessary when a question arises as to a person’s correct age as it relates to court proceedings. Typically, if a person is accused of a crime, it may be significant to determine if the individual is a minor and therefore subject to the juvenile court jurisdiction or whether the person has reached adulthood, where he or she would be prosecuted as an adult (Chapter 13). Each of these subdisciplines of forensic dentistry is discussed in one or more of the chapters of this book.
One area of forensic dentistry merits additional discussion. Forensic bitemark evidence to determine identity has become controversial over the last decade and has undergone a fundamental challenge by the greater scientific community. The catalyst for this change was the development and acceptance of DNA identification genetic testing, which is now considered to be the gold standard of biological human identification. Genetic DNA identification began to be used in the late 1980s and, in cases where the traditional fingerprint or dental identification cannot be done, has dominated the field of human identification.
DNA profiling over the past decade is the most significant advance in forensic science since the development of fingerprinting in the 1900s. DNA analysis has now set a high standard against which other forensic sciences are being judged. A working knowledge and understanding of the development and use of forensic DNA identification sciences is therefore essential to all scientists who practice in other areas of the forensic sciences. Not only has DNA identity testing redefined the standard of acceptability of other scientific evidence, but it has also fostered an awareness among juries that non-DNA-based identification techniques are less supported scientifically 6 Forensic dentistry and, in some cases, should be less accepted than DNA profiling as a method of scientific investigation.
Understanding all of the identification sciences, including DNA typing, how each developed, and how they are applied to specific casework, is essential to the forensic dentist. They are discussed in the following chapters.
Forensic DNA typing evolved from medical diagnostic techniques.
Medical diagnostic DNA typing involves clean samples from known sources.
In contrast, forensic DNA typing involves samples that are often degraded, contaminated, and may originate from multiple, unknown sources. Forensic DNA analysis also involves matching of samples from a wide range of alternatives present in the population. Except in cases where the DNA evidence excludes a suspected donor, assessing the significance of an apparent match requires a statistical analysis of population frequencies using a scientifically reliable database.
There are different types of DNA that are of interest to forensic scientists. They include nuclear DNA, mitochondrial DNA, and Y chromosome DNA. The DNA sequence, or order, of the base pairs is the same for every cell in a person’s body that has a nucleus, with the exception of reproduc-
tive cells (ova and sperm), each of which contains only one-half of that person’s DNA.
Approximately 99.9% of the sequence of the 3.3 billion bases is identical for all humans and performs the same function. However, approximately 1/1,000 of the sequence of the DNA molecule is different among al l individuals, with the except ion of ident ical mult iple birth sibl ings
(twins, triplets, etc.). The fact that people vary to this extent allows forensic scientists to determine whether DNA from a particular evidence sample could or could not have originated from a known person. DNA profiling is a catchall term for a wide range of methods for studying genetic variations.
DNA technology for human identity purposes was designed for detection of variation (polymorphism) in specific DNA sequences. Forensic scientists have identified multiple small segments, or loci, where the DNA strand varies among groups of people. Highly variable loci are called polymorphic and are useful to identify biological material as unique.
Mitochondrial DNA (mtDNA) is a small genome that is found multiple times in the cytoplasm of each cell surrounding the nucleus. Mitochondrial DNA is passed from a mother to each of her children. A man’s mtDNA is inherited from his mother, but he does not pass it on to his children. This
maternal inheritance pattern has two important implications in forensic testing. The first implication is advantageous; the mtDNA of only a single maternal relative, even distantly related, can be compared to the mtDNA of another individual, for instance, the skeletal remains of an unidentified body, and help to solve both a missing person case and an unidentified body case.
The second implication is disadvantageous; mtDNA is not a unique identifier. science, the law, and Forensic identification Because maternal relatives share the same mtDNA type, the individual source of a biological sample can never be conclusively identified with mtDNA.
In a similar manner to how mtDNA is inherited from the maternal parent , the Y chromosome is inherited (only by males) from the male parent.
All members from the same paternal lineage will therefore have the same Y-STR (short tandem repeat) profile. The STR genetic markers present on the Y chromosome may be used to obtain the genetic profile of the male donor(s) in mixtures of body fluids from males and females. Y-STR analysis will only target the Y chromosome; the DNA from the female contributor will be ignored.
Other mixture cases in which Y-STR analysis may be useful include sexual assaults involving saliva/saliva and saliva/vaginal secretion mixtures and instances in which the postcoital interval between the incident and the collection of intimate samples from the victim is greater than two days. DNA and DNA profiling are discussed in detail.
In order to understand the present status of forensic dentistry as a forensic identification science within the overall forensic science community , it is helpful to understand and trace the history of the development of forensic dentistry. As with many changes in our American society, forensic dentistry emerged as the result of landmark events (cases) that established and shaped forensic dentistry as a useful scientific tool within the greater forensic science legal community. The issue of the scientific admissibility of bitemark evidence was established in 1976 in a landmark case in California. The use of bitemark evidence after that case grew dramatically and bitemark evidence became a sought-after identification technique by law enforcement and prosecutorial agencies. Additional new bitemark identification methods were developed and used in thousands of cases throughout the United States and around the world.
In a noteworthy case from the state of Florida, a clean-cut serial killer, originally from Washington state, was convicted and eventually sentenced to death based upon bitemark evidence. The bitemarks identified at autopsy were ultimately pivotal evidence against him. The significance of this case sent a clear message to law enforcement in the United States and elsewhere that bitemark evidence could be a critical link in establishing proof of identity and obtaining a conviction. The case received widespread media attention , which resulted in public acknowledgment and acceptance of bitemark evidence (see Bundy in Chapter 14).
Beginning in the later half of the 1990s, the forensic science community was shaken by numerous instances where errors occurred in cases and individuals were exonerated after a determination was made that they were wrongfully convicted. The problem of innocent people being convicted and unjustly imprisoned for crimes they did not commit became a growing national concern that received public acknowledgment by politicians and caught the attention of the general public, with more cases arising in which DNA identity
testing technology exonerated factually innocent people. A number of DNA exoneration cases involve forensic science errors relating to evaluation of trace and biological evidence such as hair comparison and serology evidence.
DNA exonerations also occurred where the person was convicted by forensic dentistry using expert bitemark identification analysis. In the discipline of forensic dentistry, a milestone case of a wrongful conviction was the case of Ray Krone, convicted and sentenced to death for a
capital murder. He was the hundredth person in the United States who had been sentenced to death to walk free from prison since the reinstatement of the death penalty in the United States in 1977. The bitemark evidence was evaluated independently for the prosecutors by two forensic dentists, one of which was an American Board of Forensic Odontology (ABFO) board-certified forensic dentist who said positively, “better than a fingerprint,” the bitemark matched the suspect. “The bite marks on the victim were critical to the State’s case. Without them, there likely would have been no Jury submissable case against Krone.
Again, this case and its unusual and provocative outcome will be examined in the bitemark chapter.
Another bitemark conviction followed by a DNA exoneration will also be discussed. The suspect was sentenced to death for the murder of his girlfriend’s three-year-old daughter. Even though other forensic dentists concluded that the marks were not even bitemarks, the jury found him guilty.
The case demonstrated again that DNA collected from a crime victim can prove actual innocence in cases even where seemingly reliable evidence persuaded a jury to convict a person and sentence that person to death.
1.5 Conclusion
The investigation of bitemark cases by forensic dentists has necessarily evolved as the result of deficiencies uncovered after convictions that relied on bitemark evidence were overturned by DNA evidence. Improved technology and an increasing awareness of previously untested assumptions by forensic dentists have developed. This is the result of a concerted effort by some forensic dentists to build a solid scientific foundation and reliable protocols for bitemark comparisons. As a direct result of past mistakes there is now a better understanding by forensic dentists of the inherent variability and resulting distortion of marks left by human teeth in human skin. Although much work remains ahead, progress has been made. There is an increasing acceptance by forensic dentists that there is rarely, if ever, a scientific basis to justify an opinion that a specific person in an open population made a bitemark on human skin with scientific certainty, be it total or reasonable, science, the law, and Forensic identification based solely on the analysis of the pattern information. Therefore, a “positive match” in these cases is not scientifically supportable.
Those forensic dentists who have accepted the lessons of DNA exoneration cases have promoted an emphasis on conducting objective empirically based scientific research that will support bitemark opinion evidence and hold that evidence to a higher, more reliable scientific standard. One suggested approach being discussed by some forensic dentists is to unify the bitemark pattern analysis to the DNA profile testing as part of a single scientific study rather than independent scientific investigations.
This proposed method would avoid situations were the DNA and bitemark analysis are not in agreement. Scientific studies being performed by forensic dentists are expected to demonstrate that there are reliable methods and approaches to comparing bitemark evidence that minimize the potential for subjective bias and other factors that have, in the past, led to errors. As these studies are examined and other studies are undertaken by the forensic dental community they are expected to improve this troubled area of forensic science.
References
1. Federal Rule of Evidence 702.
2. Federal Rule of Evidence 104(a).
3. J. Wigmore, Evidence §556 at 751 (Chadbourn RN Rev. 1979).
4. Federal Rule of Evidence 401.
5. Frye v. United States (D.C. Cir. 1923) 293 F. 1013.
6. Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) 509 U.S. 579.
7. Frye v. United States (D.C. Cir. 1923) 293 F. 1013.
8. Frye v. United States (D.C. Cir. 1923) 293 F. 1013.
9. Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) 509 U.S. 579.
10. Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) 509 U.S. 579.
11. Kumho Tire Co., Ltd. v. Carmichael, et al. (1999) 526 U.S. 137.
12. U.S. Congress, Office of Technology Assessment, Genetic Witness: Forensic Uses of DNA Tests, OTA-BA-438 (Washington, DC: U.S. Government Printing Office, July 1990), 3–4.
13. State of Arizona v. Ray Milton Krone (1995) 182 Ariz. 319, at pp. 322, 897, P.2d 621, at p. 624.
14. Vale, G., “Coordinating the DNA Pattern Analysis Studies in Bite Mark Cases,” in Proceedings of the American Academy of Forensic Sciences, Vol. XIII, February 2007.
