Let’s think for a moment concerning what our wish list would be for bitemark analysis, our profession’s only controversial subject. I would start with an admission and publication from the ABFO of the noted and significant weaknesses that exist at this time in the field. Inferring from its contents, the ABFO’s Guidelines and Standards imply that all things have not been going well. This document expresses some technique recommendations and establishes a few limits on the behavior and language used by forensic dentists. It is not comprehensive since it is silent regarding the scientific basis of dental “uniqueness” determinations by our membership, but its intentions are good and progress is being made. Now is the time to analyze the basic weaknesses and failings of this field’s scientific underpinnings. This article is a short discussion of the biggest weakness and contains a suggestion to minimize the current high degree of risk that exists when bitemark analysis is presented in court.
Taking a historical viewpoint, the early (Texas, 1954)(1) acceptance of bitemark analysis by the U.S. appellate courts really proved a disservice to all participants and future trials. For the sake of this discussion, discount the apparent details of the cases like Marx(2) (California, 1975) which generally contained significant three-dimensional patterns in skin injuries or foodstuffs. The quality of these cases of precedent might not be representative of the majority which followed. There was, however, little science involved in the ultimate opinions dentists delivered in any of these cases. The appellate opinion in Marx realized this when bitemark admissibility was approved on the basis of the “trier of fact” (usually the jury) making their own determination from the evidence presented. Jury acceptance of bitemark testimony is no substitute for population studies and reliability testing. The “generally accepted” methods in use haven’t changed much and the glaring weakness is in the lack of pragmatic determination of “uniqueness” as seen in bitemarks on skin and inanimate objects. Hundreds of cases have occurred since the 1970′s and the issue of individuation has not been resolved scientifically. This place’s odontology at the bottom of the list of other forensic disciplines. Maybe Questioned Document Examination is worse off. There is no reliable way of saying, other than colloquially, that one or more tooth marks seen in a wound are conclusively unique to just one person in the population. Because of this vacuum, value judgements abound in our discipline. Proffering the testifying expert’s years of experience is a popular means of “proving” uniqueness.” He or she has seen more bitemarks. This misses the scientific point and is misleading to a lay jury that is given the responsibility of filtering good science from bad. The confidence level of expert testimony must be based on data available to BOTH the dentist and the court. This scientific data does not exist. Until this changes, the admissibility of bitemark analysis should be limited to a “possible” determination. The odontologist doesn’t have a basis to expand an opinion beyond that. Marks in skin can be spatially associated to the edges of teeth by trained dentists. That is within the realm of physical comparison methodology. The “unique” or “reasonable dental certainty” description currently used to characterize a positive match are not supported by anything other than personal opinion. That is the reason for this proposed limitation on bitemark testimony.
There have been and will continue to be cases where the defendant’s teeth and an unknown bite pattern shows a common pattern and shape. The determination of common similarities equaling a finding of uniqueness can’t be made on such general features. The equation using values of 1 to 4 (one being common) for these generic features such as arch width and tooth width should not be 1x1x1x1=4. The Milone(3) case and its derivative commentaries(4),(5) should be read by everyone to underscore this limitation.
I also propose that a bifurcation must take place in possible value of different types of bitemarks. A three dimensional bite, as in Marx (on a nose), allows for much more accuracy in the “wound to teeth” comparison. Questions of spatial relationships are substantially answered and discrepancies leading to subjective visualization are minimized. The answer is demonstrable and the commonly used syllogism of “its much like a toolmark” is applicable. A two-dimensional wound is a separate and much greater challenge. These cases lack “toolmark” clarity and are the foundation for uncontrolled opinion and poor sensitivity and specificity in analysis.
Research must progress to raise the current anecdotal level of individuation in contemporary bitemark analysis. A concerted effort to find funding and research facilities has to be done by this organization. It will be the cheapest assurance that our future in court will be positive, rather than controversial. After the research is done, the “possible”might then become “unique.”
1. Doyle v. State, 159 Tex. C.R.310, 263 S.W.2d 779 (Jan 20, 1954)
2. People v. Marx, 54 Cal.App3d 100, 126 Cal.Rptr. 350 (Dec. 29, 1975)
3. People v. Milone, 43 Ill.App.3d 385, 356 N.E.2d 1350 (Nov. 12, 1976)
4. U.S. ex rel. Milone v. Camp, Slip opinion (U.S. Dist. Court, N.D.IL; Sept 29, 1992)
5. Milone v. Camp, 22 F.3d 693 (7th Cir.) (Apr. 21, 1994)
About the Author: C.Michael Bowers provides expert and criminal litigation support in matters pertaining to forensic dentistry and DNA profiling. Originally published at Vol. 4, No. 2, December 1996; American Board of Forensic Odontology Newsletter.