How the flawed ‘science’ of bite mark analysis has sent innocent people to prison

"The field of forensics has reached an important moment. In 2009, the National Academy of Sciences published a congressionally commissioned report on the state of forensic science in the courtroom. The report was highly critical of a wide range of forensic specialties, from fingerprints to hair and fiber analysis to blood spatter analysis. It found that many of the claims forensic analysts have been making in courtrooms for decades lacked any scientific foundation to back them up. Yet judges and juries have taken and continue to take those claims as foolproof science, often because the experts themselves frame them that way.

The report was particularly critical of an area of forensics loosely known as pattern matching. That area encompasses a group of largely subjective specialties in which an analyst looks at two pieces of evidence, such carpet fibers, hair fibers or marks made by tools, and simply declares based on his or her experience and expertise whether the two are a match.

Bite mark analysis is also part of this group. But even within the pattern matching disciplines, the NAS report singled out bite mark matching for some especially harsh criticism. The report found “no evidence of an existing scientific basis for identifying an individual to the exclusion of all others.” The problem is that this is precisely what bite mark analysts do — and what they have been doing for decades."