GIST: "There is little evidence that bite marks on a crime victim’s skin allow reliable identification of the perpetrator. For 19 years, Gerard Richardson sat in prison in New Jersey wondering how forensics experts had got his case so wrong. His conviction for a 1994 murder was based on a bite mark on the victim’s body that seemed to match his own teeth; it was the main physical evidence linking him to the crime. Last year, he was exonerated when DNA taken from the same bite mark turned out not to be his. According to the Innocence Project in New York, which tracks wrongful convictions, more than half of DNA exonerations involve faulty forensic evidence from crime labs and unreliable methods such as bite-mark analysis. Cases such as Richardson’s are one reason why the US Department of Justice and the National Institute of Standards and Technology (NIST) have now created the first US national commission on forensic science. The panel of 37 scientists, lawyers, forensics practitioners and law-enforcement officials met for the first time this week in Washington DC, and aims to advise on government policies such as training and certification standards. In March, NIST will begin to set up a parallel panel, a forensic-science standards board that will set specific standards for the methods used in crime labs.........The value of certain techniques is often overstated in court cases, says Simon Cole, who studies the history of science in the criminal justice system at the University of California, Irvine. Finger­print comparison, for instance, is often presented as an exact science, but researchers have only recently begun to study just how well people can do the matching. A 2011 study found that professional examiners matched two finger­prints incorrectly once in every 1,000 times, and missed a correct match 7.5% of the time (B. T. Ulery et al. Proc. Natl Acad. Sci. USA 108, 7733–7738; 2011). Cole would like the standards board to define a ‘match’ precisely, and to assess the extent to which different methods yield different results. The standards board could also question how widely some of the more dubious techniques should be used. Mary Bush, a forensic dentist at the State University of New York in Buffalo, says that there is little evidence that bite marks left in skin can reliably identify perpetrators. In her lab, moulds of different sets of teeth were clamped into the skin of cadavers. Digital images of the marks were then analysed. Often, the marks could not be used to identify the teeth responsible. Gregory Golden, president of the American Board of Forensic Odontology, argues that the method is useful for eliminating suspects or determining whether a bite mark is human. According to the Innocence Project, however, at least 15 people whose convictions involved bite marks and who served time in prison have been exonerated through DNA evidence since 1993. That alone suggests that the method should be investigated, says Bush. “We’re fighting 30 years of precedent.”"

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