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Looming decision over bite-mark analysis in Texas may cause nationwide domino effect in courtrooms, say UB forensics researchers

UB forensics researchers Mary and Peter Bush at the South Campus Instrumentation Center. Photo: Douglas Levere

Texas commission’s decision on validity of bite-mark evidence could lead push for exonerations for hundreds of people across country, starting in Texas

Release Date: February 11, 2016

“With no scientific basis supporting this technique, the analysis can amount to no more than subjective guessing.”
Mary Bush, associate professor of restorative dentistry in the UB School of Dental Medicine, on the validity of bite-mark evidence.

BUFFALO, N.Y. – 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, Feb. 11, 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 the University at Buffalo South Campus Instrument Center, and Mary Bush, associate professor of restorative dentistry in the UB School of Dental Medicine.

“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.”

Bite-mark analysis, which compares the teeth of crime suspects to the bite-mark patterns on victims, is widely accepted in criminal courts and is often 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 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 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 that 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 research, completed with H. David Sheets, PhD, professor of physics at Canisius College, and Raymond Miller, DDS, clinical associate professor of oral diagnostic science in the UB School of Dental Medicine, are among the largest studies conducted on bite-mark analysis, and are the first to use human-skin models.

The studies were 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. They were also 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 on bite-mark evidence were later exonerated after DNA testing, according to the Innocence Project.

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.

A previous 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 their end as evidence in courtrooms, and potentially overturn convictions for many people while there is still time left, say the Bushes.

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