GPSolo September 2007
Bite Mark Evidence
Courts have admitted bite mark comparison evidence in homicide, rape, and child abuse cases. In virtually all the cases, the evidence was first offered by the prosecution. A typical case involves the identification of a defendant by matching his dentition with a mark left on the victim. In several cases, however, a victim’s teeth have been compared with marks on a defendant’s body. A few cases have involved bite impressions on foodstuffs found at a crime scene, and one case involved a dog bite. No reported case has rejected bite mark evidence. Indeed, its acceptance is so well established that courts have taken judicial notice of the validity of bite mark evidence.
Given recent DNA exonerations, it is critical that bite mark evidence be challenged.
Empirical research. Despite this judicial acceptance, there is little empirical research supporting bite mark identification. As one commentary points out, “the fundamental scientific basis for bite mark analysis has never been established.” Even supporters acknowledge shortcomings: The research suggests that bite mark evidence, at least that which is used to identify biters, is a potentially valid and reliable methodology. It is generally accepted within the scientific community, although the basis of this acceptance within the peer-reviewed literature is thin. Only three studies have examined the ability of odontologists to utilize bite marks for the identification of biters, and only two studies have been performed in what could be considered a contemporary framework of attitudes and techniques.
Theory of uniqueness. Identification of a suspect by matching his dentition with a bite mark found on the victim of a crime rests on the theory that each person’s dentition is unique. In this respect, bite mark comparisons are based on the same principle as the identification of a deceased person by means of his dentition. Although the courts have accepted this theory, there are significant differences in the application of these two uses of forensic dentistry. In 1976, when bite mark comparisons were first studied, one authority noted the following problems:
[Bite] marks can never be taken to reproduce accurately the dental features of the originator. This is due partially to the fact that bite marks generally include only a limited number of teeth. Furthermore, the material (whether food stuff or human skin) in which the mark has been left is usually found to be a very unsatisfactory impression material with shrinkage and distortion characteristics that are unknown. Finally, these marks represent only the remaining and fixed picture of an action, the mechanism of which may vary from case to case. For instance, there is as yet no precise knowledge of the possible differences between biting off a morsel of food and using one’s teeth for purposes of attack or defense (S. Keiser-Nielsen, Forensic Odontology, 1 U. Toledo L. Rev. 633, 636 (1969)).
In sum, bite mark identification depends not only on the uniqueness of each person’s dentition but also on “whether there is a [sufficient] representation of that uniqueness in the mark found on the skin or other inanimate object.”
Subjectivity. It is easier to conclude that a person’s dentition and a bite mark do not match than it is to find a match. This is due to the fact that any unexplainedinconsistency between the bite mark and the dentition means that the suspect could not have made the bite mark. According to some experts, a positive identification may still be possible even though some inconsistencies are present, provided the inconsistencies can be explained. One commentator has written:
There may, of course, be slight variations that are consistent—i.e., all of the bite marks are on a larger (or smaller) arch than the teeth themselves. In other words, depending on the location of the bite marks, whether the person (victim or suspect) was passive, unconscious, or struggling, the degree of sucking that occurred during the biting and manual manipulation, the forensic odontologist may be able to explain “consistent variations” in the comparison. (Norman D. Sperber, Forensic Odontology, in Practising Law Institute, Scientific and Expert Evidence 721, 747-48 (E. Imwinkelried ed., 1981).
Although the expert’s conclusions are based on objective data, the opinion is essentially a subjective one. Given the subjective character of bite mark comparisons, it is not surprising to find qualified experts disagreeing in individual cases. Often, the disagreement is over whether a wound is even a bite mark.
DNA exonerations. The availability of DNA analysis has altered the debate on the reliability of bite mark evidence. In State v. Krone, 897 P.2d 621, 622 (Ariz. 1995), two experienced experts concluded that the defendant had made the bite mark found on a murder victim. Their testimony was crucial because there was little other evidence of the defendant’s guilt. However, he was later exonerated through DNA testing. In Ege v. Yukins, 380 F. Supp. 2d 852 (E.D. Mich. 2005), the court reviewed an expert’s testimony in other cases, noting that the expert had opined in one case that “the chances of someone else having made the mark would be 4.1 billion to one. Mr. Otero [the defendant in that case] was subsequently exonerated when DNA from semen found in the victim’s body was shown to be from someone other than Mr. Otero and the prosecution dismissed its case against him.” In Otero v. Warnick, 614 N.W.2d 177, 178 (Mich. App. 2000), a forensic dentist’s testimony suggested that the “plaintiff was the only person in the world who could have inflicted the bite marks on [the murder victim’s] body. However, the Detroit Police Crime Laboratory released a supplemental report that concluded that the plaintiff was excluded as a possible source of DNA obtained from swabs taken from [the victim’s] body.”
In Burke v. Town of Walpole, 405 F.3d 66 (1st Cir. 2005), the expert said “Burke’s teeth matched the bite mark on the victim’s left breast to a ‘reasonable degree of scientific certainty.’ That same morning . . . DNA analysis showed that Burke was excluded as the source of male DNA found in the bite mark on the victim’s left breast.”
Given this background, it is critical that bite mark evidence be challenged. In Ege, the district court found ineffective assistance where counsel failed to object to bite mark evidence involving an overwhelming mathematical probability. The court observed: “In this case, it is difficult to conceive of a reason for not objecting to the bite mark evidence and the statistical opinion. . . . Since the bite mark evidence was the only physical evidence connecting the petitioner to the crime scene at the time of the murder, challenging its admissibility likely would have been a sound decision with no adverse consequence.” In Wilhoit v. State, 816 P.2d 545, 546 (Okla. Crim. 1991), even trial counsel stated in an affidavit that “there was no strategic reason for his not pursuing the bite-mark evidence nor for not using a bite-mark expert.” The court found that counsel’s omission was “even less excusable in light of the fact that the Wilhoit family had hired a forensic odontologist who was available to examine the bite-mark evidence.”
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Paul C. Giannelli is the Albert J. Weatherhead III and Richard W. Weatherhead Professor of Law at Case Western Reserve University School of Law.