Evaluating "Bite" Evidence

State trial court erred by admitting expert testimony regarding identity of bite marks on homicide victim and the opinion that there was only a "3.5 million to one" possibility that the bite marks would match the dentition of someone other than the defendant; federal habeas corpus relief granted as the expert lacked data supporting his estimate of the rarity of the defendant's bite mark and because the expert testimony deprived the defendant of her Fifth Amendment due process right to a fair trial, in Ege v. Yukins, 485 F.3d 364 (6th Cir. April 24, 2007) (No. 05–2078)

Using bite marks as identification evidence appears to have received a mixed reception in the courts. Typically for this evidence, a dentist as an expert witness, comparing the bite marks on a victim with the defendant's teeth -- either through the use of impressions of the defendant's teeth, or by appearance of bite marks on the victim. While this forensic odontology has been used more occasionally in state court trials, the Sixth Circuit explained the need for caution because this evidence "carrie[s] an aura of mathematical precision pointing overwhelmingly to the statistical probability of guilt, when the evidence deserve[s] no such credence." Ege v. Yukins, 485 F.3d 364, 376 (6th Cir. April 24, 2007) (quoting district court opinion).

Bite Mark Evidence

In the case, defendant Ege was charged with having murdered a woman for whom she was "furiously jealous." The victim's body was found "bludgeoned and stabbed to death" and the initial police investigation was inconclusive concerning the identity of the perpetrator. Eight years later, in a second inquiry, investigators reexamined what was characterized as "a mark on the victims' cheek," which was identified to be a bite mark. As explained by the circuit, this evidence was based on an expert:

The prosecution's expert witness, Dr. Alan Warnick, [who] opined that the mark found on [victim] Thompson's cheek, which the original autopsy report had concluded was liver mortis, was actually a bite mark. Dr. Warnick was unable to examine the actual injury, because Thompson's body was too badly decomposed upon exhumation nine years after the murder. Thus, Dr. Warnick relied on photographs of the mark which had been taken at the time of the initial autopsy, in 1984. Dr. Warnick compared dentitions of several suspects raised by the defense and found that none of them could have made the bite mark. He also checked Ege's dentition and concluded that it was highly consistent with the bite mark.
Ege, 485 F.3d at 368.

Lack Of Foundation

The problem with this evidence at trial was that the expert's assessment that the bite mark was left by the defendant "was entirely without foundation), we cannot say that it should have been similarly obvious to Ege that the substance of the physical evidence—at least as presented by Dr. Warnick—was complete bunk." The circuit noted the presentation of this evidence was troublesome. First, in that it seemed to be so precise, for example the circuit noted the following exchange in the presentation of the evidence:

Now, Doctor, with regard to your testimony, you indicated that it's highly consistent with the dentition of Defendant Carol Ege; is that correct?
Okay. With regard to—let me ask you a question. Let's say you have the Detroit Metropolitan Area, three, three and a half million people. Would anybody else within that kind of number match like she did?
No, in my expert opinion, nobody else would match up.
The circuit noted that the lack of foundation for this evidence had been noted as well by the state appellate court, which wrote:
This Court agrees that the testimony regarding the probability that the bite matched the defendant lacked a proper foundation. Expert forensic testimony regarding identification of the defendant based upon a statistical analysis requires a proper foundation. To make a statistical evaluation it is necessary to know the frequency of a particular characteristic in the population. The probability of any combination of known characteristics is equal to the product of the frequency of each. In this case there was no evidence offered to support the expert's conclusion regarding the probability that the defendant made the mark. In other words, the expert did not testify that he had identified particular features of the bite mark that had a known rate of occurrence. Neither did the expert did [sic] testify that he had multiplied these values to reach his conclusion.
Ege, 485 F.3d at 374 (citing People v. Ege, Oakland Circuit Case No. 93–125655–FC, January 11, 2000, at 5 (internal citation omitted) (emphasis added in original)).

The Error Not Harmless

Where the federal courts differed from the state courts concerned whether the error in admitting the bite mark identification evidence was a harmless error. The circuit concluded that the error was extremely prejudicial:

Bite mark evidence may by its very nature be overly prejudicial and unreliable, but it may nevertheless be admitted under Michigan evidence law, and we do not question the Michigan courts' judgment with respect to admission of the bite mark evidence standing alone. However, Dr. Warnick's statement that among the 3.5 million residents of the Detroit metropolitan area, Ege's teeth, and only Ege's teeth, could have made the mark on Thompson's cheek, was without doubt highly prejudicial. It strains credulity to think that a jury hearing Dr. Warnick's testimony would not immediately place Ege at the scene of Thompson's violent murder, if only her teeth, and not those of 3,499,999 other Detroit residents, were linked to a bite mark on Thompson's cheek. Such “testimony expressing opinions or conclusions in terms of statistical probabilities can make the uncertain seem all but proven, and suggest, by quantification, satisfaction of the requirement that guilt be established ‘beyond a reasonable doubt.’ ” Furthermore, the injurious effect of Dr. Warnick's probability testimony was not in any way diffused by the experts put on by Ege's counsel. Both of these experts opined that the mark on Thompson's cheek was livor mortis, and not a bite mark, but neither directly refuted Dr. Warnick's methods in coming to his 3.5 million–to–1 probability determination. Thus, even if a majority of jurors did not believe Dr. Warnick's testimony that the mark was a bite mark, the minority who did would have been inclined to think that such a mark could only have come from Ege.
Ege, 485 F.3d at 376-77 (citing People v. Carlson, 267 N.W.2d 170, 176 (Minn. 1978)).


In Ege, the Sixth Circuit expressed several reservations about the merits of bite mark evidence. While acknowledging that a state was free to adopt evidence procedures that would permit use of bite evidence, the circuit noted a 1978 article that suggested that a major barrier to greater adoption of bite evidence was that it was a more "direct" sort of evidence. The impact of a mistake in its interpretation would have a greater impact on the case than would mistakes with other types of expert evidence. A mistake in the interpretation of many commonly accepted forms of expert evidence, such as fingerprint evidence, is rarely fatal since "they rarely decide a case alone, but tend to link a defendant to the scene of the crime or an object involved in the crime. By contrast, bite marks, in the usual case, will be conclusive of the guilt issue: the logical distance between the fact of biting and the ultimate issue of guilt is short. Thus, admission of irrelevant bite mark evidence may be particularly prejudicial to the defendant." Ege, 485 F.3d at 377 n.6 (quoting Adrienne Hale, The Admissibility of Bite Mark Evidence, 51 S. Cal. L. Rev. 309, 326 (1978)).


Federal Rules of Evidence