Of all of the methods studied in the 2009 National Academy of Sciences’ report on forensic science, forensic odontology — the analysis of bite marks to identify the perpetrators of crimes — has come under some of the harshest criticism. And now an effort is underway to keep it out of courtrooms for good.
This article by the Associated Press examined “decades of court records, archives, news reports and filings by the Innocence Project in order to compile the most comprehensive count to date of those exonerated after being convicted or charged based on bite mark evidence.” Typically, the evidence consisted of testimony by forensic dentists identifying marks on the bodies of victims (usually in cases of murder or sexual assault) as coming from the defendant’s teeth. According to the AP, since 2000, DNA identification has overturned one after another of these cases, throwing the entire “discipline” into question, and rendering it nearly obsolete.
Critics make two main claims against forensic odontology. First, there’s no scientific proof that a bite mark can be matched to any particular set of teeth. There is no data, no experimental evidence — nothing — on which to base the idea that forensic odontology can make reliable identifications. Second, human skin — almost always the site of the bite mark in question — does not reliably “record” bite marks, since the skin itself changes over time, even after death. Because the skin changes shape, consistency, color, and even size after the mark is made, this makes bite marks, and the method itself, inherently unstable.
Yet the dentists, who belong to the American Board of Forensic Odontology, insist that their methods of making identifications of the source of bite marks are reliable; it’s just that some forensic dentists are, well, not too good or biased. “The problem lies in the analyst or the bias,” said Dr. Frank Wright, a forensic dentist in Cincinnati. “So if the analyst is … not properly trained or introduces bias into their exam, sure, it’s going to be polluted, just like any other scientific investigation. It doesn’t mean bite mark evidence is bad.” It’s the familiar refrain: it’s just a few bad apples, not the whole barrel. But according to the AP:
Only about 100 forensic dentists are certified by the odontology board, and just a fraction are actively analyzing and comparing bite marks. Certification requires no proficiency tests. The board requires a dentist to have been the lead investigator and to have testified in one current bite mark case and to analyze six past cases on file — a system criticized by defense attorneys because it requires testimony before certification…The consequences for being wrong are almost nonexistent. Many lawsuits against forensic dentists employed by counties and medical examiner’s offices have been thrown out because as government officials, they’re largely immune from liability. Only one member of the American Board of Forensic Odontology has ever been suspended, none has ever been decertified, and some dentists still on the board have been involved in some of the most high-profile and egregious exonerations on record.
It’s worth noting that there’s nothing wrong with other uses of forensic dentistry, such as identifying human remains from teeth by matching them to existing dental records; that type of forensic work is generally rock solid and remains unchallenged by critics. But on identification of perpetrators through bite mark analysis, the question is different: when a forensic “science” has as dismal a record as forensic odontology does, and no scientific proof of its validity exists, can anything justify allowing the use of bite mark evidence to convict a person of a crime?