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UPDATE

On March 19, 2014, after At Buffalo went to press, Ohio’s Ninth District Court of Appeals reversed the decision exonerating Douglas Prade. His lawyers have filed a notice of appeal in the Ohio Supreme Court.

False Impressions

Mary and Peter Bush of the UB dental school had no intention of entering the controversial bite mark debate. Now they’re at the forefront of a movement to free wrongfully convicted prisoners and banish bite mark evidence from the courtroom.

 Mary and Peter Bush

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

Story by Nicole Peradotto

“In recent years, increasingly sophisticated DNA testing has resulted in numerous exonerations of people convicted on bite mark evidence.”
Chirs Fabricant, Director of strategic litigation at the Innocence Project

On the morning of Nov. 26, 1997, Margo Prade, a prominent doctor in Akron, Ohio, was found slumped behind the wheel of her minivan in a parking lot outside her medical office. She had been shot six times.

There were no witnesses. Investigators didn’t find fingerprints at the scene or locate the gun. But the killer in one of Akron’s most notorious crimes left behind physical evidence that would become central to the state’s case against Prade’s ex-husband: a bite mark imprinted on her left arm.

During the trial, a forensic dentist testified that Douglas Prade’s teeth matched the impression made through his ex-wife’s blouse and lab coat. Based largely on the bite mark evidence, the former police captain was convicted and sentenced to life in prison.

Fourteen years later, as Prade continued to maintain his innocence from inside the Madison Correctional Institution, Mary Bush (DDS ’99), associate professor of restorative dentistry at UB’s School of Dental Medicine, received a call that would propel her into the campaign to overturn his conviction.

When she and her husband, Peter, began reporting the results of their research on bite marks in 2009, they anticipated that their findings would reverberate beyond academic circles. What they didn’t foresee was how quickly it would happen—or how deeply enmeshed they’d become in the high-stakes debate over the validity of bite mark analysis.

“The impact of any research can take years to realize, so we thought it would be some time before we’d see that impact,” says Peter, a microscopy expert who directs the South Campus Instrumentation Center at the dental school. “We were contacted to testify in our first trial a year after the first study was published. It all happened very quickly and had some unintended consequences.”

Former Akron Police Capt. Douglas Prade

Former Akron Police Capt. Douglas Prade gets emotional while answering questions during an interview with the Columbus Dispatch before being released from prison. Photo: The Columbus Dispatch/ MCT /LANDOV

The Bushes’ findings spilled off the pages of scholarly journals and into the criminal courts because they challenged two essential assumptions on which the forensic discipline of bite mark analysis rests: first, that human skin reliably records the patterns of one’s teeth, and second, that dental impressions, like fingerprints, are distinct enough to be linked to specific individuals.

When he read the Bushes’ work, Chris Fabricant, director of strategic litigation at the Innocence Project, recognized it as powerful ammunition in the organization’s efforts to exonerate wrongfully convicted people through DNA testing.

“This is groundbreaking and desperately needed foundational research in an area of forensic science that previously had none, despite its admissibility in criminal courts,” says Fabricant, who recruited Mary Bush to testify in the Prade hearing in 2012 and helped coordinate her testimony in a pivotal New York City case that same year. “Their findings call into doubt convictions that rest entirely on bite mark evidence and underscore the steady drumbeat of wrongful convictions based on bite mark evidence that are later overturned based on DNA evidence. There are at least one, two, three cases a year.”

Although bite mark analysis—the practice of comparing dental impressions made on a victim’s flesh with a suspect’s dentition—has not been subjected to rigorous scientific scrutiny, it has been allowed in criminal courts for more than 40 years. It was most famously used to prosecute Ted Bundy, the 1970s serial killer responsible for the deaths of at least 30 women.

Forensic odontologists who analyze bite marks point to cases like Bundy’s, arguing that the practice has led to the conviction of many notorious criminals. When done by well-qualified, highly trained experts, they say, bite mark analysis can play a critical role in cases of abuse and murder—not only to determine culpability but to exclude suspects as well.

In recent years, however, increasingly sophisticated DNA testing has resulted in numerous exonerations of people convicted on bite mark evidence, bolstering critics’ claims that it’s junk science and should be cast out of criminal proceedings.

Against this backdrop, the Bushes and their research team initiated their first forensic studies in 2006, not in bite mark analysis, but in the field of victim identification. Their efforts resulted in an innovative database that helps identify dead people by the chemical compounds in their dental fillings, technology first applied after the crash of Flight 3407 in Clarence, N.Y., in 2009.

“We always said that we were never going to get involved in bite mark analysis because it is such a contentious issue,” Mary says. “But in 2007, a student in the dental school’s summer research project wanted to conduct bite mark research and asked us to serve as his mentors. That’s what got us started.”

During that summer, the research team set out to determine how long fabric patterns remain imprinted on the skin after someone has been bitten through clothing. Prior to the Bushes’ experiments, scientists had conducted these types of investigations with dental molds engineered to bite into a surface that serves as a surrogate for human skin—such as pig skin or dog skin—or a non-elastic biting substrate, such as Styrofoam or wax. The UB researchers were among the first to seek answers to their questions using human skin, from cadavers donated for approved academic research.

An example of bite mark research conducted on a cadaver model.

An example of bite mark research conducted on a cadaver model. Photo: © 2009 American Academy of Forensic Sciences

“As opposed to animals, the cadaver model has advantageous aspects in that you’re studying human skin, but it doesn’t bruise or swell,” Mary explains. “So you’re able to isolate some variables and look at clear indentations.”

The Bushes never intended to extend their research into bite mark analysis beyond the fabric study. But what Mary saw in that initial experiment made her realize they were only at the beginning of their inquiry.

“We made 23 impressions in the skin, and they all looked different,” she says. “There wasn’t any consistency, even though we were using the same model. And the model we used was one of my own teeth. I know what my pattern looks like, and these impressions didn’t look anything like it.”

In January of 2009, the Bushes published their first study on dental impressions in the Journal of Forensic Sciences, the peer-reviewed journal on whose editorial board Mary now serves.

A month later, a committee of the National Academy of Sciences (NAS) issued a report on forensic sciences that found significant deficiencies in the field of bite mark analysis. These included the pressure on forensic odontologists to match a bite mark to a suspect and, as with other experience-based forensic methods, the potential for “large bias” among experts in evaluating such marks.

The paper underscored the lack of rigorous research in the field, particularly large population studies to establish the uniqueness of bite marks—coincidentally, the very research the Bushes had by then started conducting, using computer analyses of dental shapes. “Our research actually anticipated the questions the NAS had,” Peter says. Those studies, also published in the Journal of Forensic Sciences, found a “significant match rate” among the dentitions of 1,100 people. In other words, a single bite mark could point to many different individuals.

“We don’t know whether people are innocent or guilty, but we know that to put someone away for years based on bite mark evidence is unjust.”
Peter Bush

In 2010, the Bushes received their first request to testify about their bite mark research. In an admissibility hearing in Alabama, the defense was challenging bite mark evidence introduced in a capital murder case against a man accused of killing his girlfriend’s 1-month-old son.

Peter Bush describes his testimony as “the most stressful two hours of my life.” Ultimately, the judge did not have to rule on the matter; the defendant pleaded guilty.

Two years later, Mary Bush testified in a potentially precedent-setting pretrial challenge in New York City. Because it was one of the first-ever hearings on the admissibility of bite mark evidence, opponents believed that a successful argument could help expel the practice from courtrooms nationwide.

The case involved the murder of 33-year-old Kristine Yitref, whose beaten and strangled body was found under a bed in a hotel near Times Square. A forensic dentist concluded that a bite mark on her body matched the teeth of Clarence Dean, a fugitive sex offender.

“I knew the opposing attorney would try to challenge my research and look for ways to discredit me,” Bush says of her two days on the stand. “But it’s still hard to be spoken to in a derogatory manner. You’re treated like you don’t know what you’re doing. The opposing side used language that denigrated our work, like saying that we were pinching dead skin using Home Depot vice grips. That’s difficult to hear.”

In a decision that the Innocence Project’s Fabricant decried as “a victory for the Flat Earth Society,” the judge ruled that the bite mark evidence would be allowed at the trial.

After returning from New York City, Mary Bush looked forward to an ebb in the bite mark controversy. It didn’t happen. Instead, criticism of both her credentials and her research methodology—initiated by advocates of bite mark analysis unhappy with her testimony in the Dean case—intensified and grew increasingly mean-spirited.

After a heated exchange that occurred in February 2013, in front of 200 scientists gathered to hear her research presentation at a session of the American Academy of Forensic Sciences’ annual meeting, Bush didn’t want to look at bite marks or accept an attorney’s call for a while.

“I didn’t anticipate that the backlash would be so vicious,” she says. “I thought I would have my professional opinion, and it would differ with the other side’s. I thought, ‘We’re professional individuals, and we’ll act in a professional manner.’ But then I was handling these nasty letters and public attacks. I guess we were naïve going into this.”

When they testify, the Bushes do so pro bono. If they accept a fee, it’s only to cover travel expenses. They never address the bite mark evidence in question, instead presenting the nature and findings of their research.

Prade hugs Jodi Shorr, administrative director for the Ohio Innocence Project, following a news conference after his release from the Madison Correctional Institution.

Prade hugs Jodi Shorr, administrative director for the Ohio Innocence Project, following a news conference after his release from the Madison Correctional Institution. Photo: Akron Beacon Journal/ MCT /LANDOV

“We don’t know whether people are innocent or guilty, but we know that to put someone away for years based on bite mark evidence is unjust,” Peter says. “Are you going to convict someone on evidence that’s shaky at best? That’s always been a motivating factor for me.”

So, too, for the Bushes, is this statistic, from an Associated Press investigative report released last year: Since 2000, at least 24 men convicted or charged with murder or rape based on bite marks have been exonerated, largely as a result of DNA testing.

On the afternoon of Jan. 29, 2013, three months after Mary Bush testified in his postconviction hearing, former police captain Douglas Prade made that list.


Nicole Peradotto is a writer and editor in UB’s School of Medicine and Biomedical Sciences.