Juries in Tennessee and around the country tend to find forensic evidence extremely compelling. This worries experts because modern forensics is sometimes based on incomplete, flawed or debunked science. About a quarter of the 2,601 people exonerated since 1989 were convicted based on forensic evidence, and 26 of them found themselves behind bars because experts claimed that they left bite marks on their alleged victims. The science surrounding bite marks has been largely discredited, and even state agencies like the Texas Forensic Science Commission have called for it to be excluded in criminal trials.
There are several problems with bite mark evidence. The way teeth are arranged cannot be used to conclusively identify an individual, and bite marks on human skin are notoriously difficult to identify. The American Board of Forensic Odontology conducted a study into bite mark evidence in 2015. Dentists asked to analyze images of bite marks were rarely able to say with any confidence that the wound was caused by a bite.
The questionable science of bite marks attracted media attention in 2015 when a Mississippi man was exonerated after spending 15 years in prison for a rape and murder that he did not commit. He was convicted in 1992 after a forensic odontologist testified with certainty that wounds on the victim’s body were his bite marks. Police found the body in a creek, and it is now believed that the wounds were caused by crawfish. The forensic odontologist was later suspended by the ABFO and ousted by the American Board of Forensic Pathology. This kind of mistake has prompted legislators in several states to pass laws allowing prison inmates to file appeals when new scientific discoveries raise questions about the evidence used to convict them. Tennessee currently has no such law.
Experienced criminal defense attorneys may pay close attention to developments in forensic science and studies like the one conducted by the ABFO. They could also call on experts of their own when prosecutors plan to introduce forensic evidence that may be based on flawed science.