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Decision on bite-mark analysis in Texas may cause nationwide domino effect in courtrooms

Peter and Mary Bush.

Research by Peter and Mary Bush has found that a single bite-mark could point to different people, including an innocent suspect, or even exclude the guilty. Photo: Douglas Levere

By MARCENE ROBINSON

Published February 11, 2016 This content is archived.

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“The decision will be influential and should cause other states to take notice. Texas may start a domino effect for much needed reform. ”
Peter Bush, director
South Campus Instrument Center

The fates of hundreds of men and women, including many on death row, hang in the balance of an imminent decision by the Texas Forensic Science Commission on the legitimacy of bite marks as evidence.

With arguments growing over the validity of bite-mark analysis, the Texas commission will gather today to determine if there is any science supporting the analysis, a decision that could be the turning point in the battle to remove this form of evidence from courtrooms, says Peter Bush, director of UB’s South Campus Instrument Center, and Mary Bush, associate professor of restorative dentistry, School of Dental Medicine.

“The decision will be influential and should cause other states to take notice. Texas may start a domino effect for much needed reform,” says Peter Bush.

Bite-mark analysis, which compares the teeth of crime suspects to the bite-mark patterns on victims, is widely accepted in criminal courts and often is presented as key evidence in prosecutions.

If the Texas Forensic Science Commission rules the science behind the analysis flawed, the “Lone Star” state would be the first to remove the form of evidence from the courtroom.

The analysis relies on the theory that dental impressions are like fingerprints, unique to every individual, and that human skin can accurately record that uniqueness.

However, research by the Bushes, which analyzed the biting surfaces of more than 1,000 sets of human dentition, found that some arrangements can be remarkably similar, making it difficult to distinguish between them.

The researchers also used scientific instrumentation to create hundreds of bite marks on cadaver skin. Results showed the pattern of an inflicted bite mark can be dramatically different than the set of teeth that created it.

In other words, a single bite-mark could point to different people, including an innocent suspect, or even exclude the guilty.

“We found the distortion in skin to be a large factor in the reliability of this forensic discipline. Skin simply doesn’t retain, with fidelity, the pattern of the teeth,” says Mary Bush.

The studies, completed with H. David Sheets, professor of physics at Canisius College, and Raymond Miller, clinical associate professor of oral diagnostic science at UB, are among the largest conducted on bite-mark analysis, and the first to use human-skin models.

The research was presented before the congressional hearing “Scientific Rigor for the Courtroom” on Capitol Hill and the U.S. President’s Council of Advisors on Science and Technology. It also was cited in significant court cases, including the trials of Douglas Prade and Clarence Brian Dean, and by the Innocence Project, an organization committed to exonerate wrongly convicted people.

At least 24 people convicted with bite-mark evidence were later exonerated after DNA testing, according to the Innocence Project.

“With no scientific basis supporting this technique, the analysis can amount to no more than subjective guessing,” says Mary Bush. “As such, it should be no surprise to see that a number of tragic errors have resulted. To date, a significant number of people have been exonerated, some after spending more than 25 years in prison for crimes they didn’t commit.”

The possibility of hundreds more false convictions adds weight to the future decision by the Texas Forensic Science Commission, a state agency that investigates complaints about misuse or neglect regarding crime laboratories.

The last investigation held by the commission, in 2010 after the much-questioned 1992 conviction and execution of Cameron Todd Willingham, led to sweeping change in arson forensic analysis.

The commission found the forensic techniques used to convict Willingham were flawed, but the investigation wasn’t completed until six years after his death.

A decision acknowledging the flaws of bite-mark analysis could spark the beginning of the end of its use as evidence in courtrooms, and potentially overturn convictions for many people while there is still time left, the Bushes say.