California Innocence Project

Bite Mark Evidence

Bite mark evidence has been introduced in trials all over the country, and sometimes has been the smoking gun leading to a conviction. Bite mark evidence, or forensic odontology, is the process by which odontologists (dentists) attempt to match marks found at crime scenes with the dental impressions of suspects. If a victim is bitten by a perpetrator during a crime and police have a suspect, odontologists can attempt to “match” the bite mark to the suspect’s teeth.

Although bite mark evidence has been used across the country in many criminal prosecutions, there is no real scientific support or research into the accuracy or reliability of bite mark evidence. Although bite mark evidence is often introduced as being close to DNA in terms of accuracy, there has been no scientific validation for the notion that a person’s dentition is unique to him or her in the same way that fingerprints or DNA are unique to each individual. Bite marks are often found at the scene of violent crimes – murders, assaults, and sexual assaults – and are extremely difficult to accurately investigate. Part of this is because victims of violent crimes can suffer multiple injuries, and what looks like a bite can actually be an unrelated injury. This is because, unlike a dental impression at a doctor’s office, bite marks are found on materials like skin, clothing, and soft tissue. Human skin is elastic; it swells, heals, and it can deform or warp a bite so that it does not align properly. Furthermore, “experts” often use pictures to compare a person’s dentition to the bite mark on the victim, increasing the unreliability of bite mark evidence.

Another problem with bite mark evidence is its similarity to other “sciences” such as fingerprint analysis (link) and firearm analysis (link): they are subjective to the person evaluating the evidence. Different experts have found widely different results when looking at the same bite mark evidence. Such subjectivity has no place being touted as science in the courtroom, as it is extremely persuasive to a jury, especially where someone has been wrongfully accused.

One of the most notable exonerations involving bite mark evidence is the Ray Krone case.  In 1992, Krone was wrongfully convicted of murder and sentenced to death.  There was no physical evidence linking Krone to the crime except for a unique bite mark found on the victim's body.  At trial, a bite mark expert testified that Krone's teeth matched the bite mark on the victim.  Upon further investigation, several experts told Krone's attorneys that the trial testimony was unreliable and the analysis was done incorrectly.  Eventually, DNA evidence proved Krone's innocence and he was released from prison in 2002.

Bite mark evidence led to the conviction of William Richards. At his trial in 1997, a forensic odontologist analyzed Richards’ teeth and a bite mark found on his wife’s body. The expert testified that only one to two percent of the population could have left this bite mark, and he could not exclude Richards as having given the bite mark. This led to Richards’ conviction. Today, the same expert says that Richards could not have left the bite mark. This recantation led to Richards’ exoneration, which has since been appealed by the District Attorney’s Office. Today, Richards remains in prison.


 

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