Widely accepted in criminal courts and often presented as key evidence in prosecutions, bite mark analysis is "far from an exact science" and can lead to false convictions, according to a new study.
Bite-mark analysis compares the teeth of crime suspects to bite-mark patterns on victims.
Historically, forensic odontologists (dentists who provide forensic dental identifications in criminal investigations and mass disasters) operate under two general guidelines when interpreting bite-mark evidence.
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First, that everyone's dental impression is unique to the individual, "similar to fingerprints," said H David Sheets, from Canisius College, New York.
Second, that human skin - the most common material on which a bite mark is inflicted - reliably records an individual's dental impression.
Bite-mark analysis is widely accepted in criminal courts and often presented as key evidence in prosecutions.
"People assume that it's close to fingerprints in terms of accuracy," said Sheets.
"But the notions that a person's dentition is unique or that the human skin can accurately record an individual's bite mark have never been validated scientifically," said Sheets, adding that bite-mark analysis is "far from an exact science."
Using a variety of dental impressions, Sheets and colleagues examined more than 1,000 human dentitions and studied hundreds of bite marks in cadaver skin.
With the help of computer analysis and applied statistics, the team then worked to match its database of bite marks to the correct dental impressions.
"When the dental alignments were similar, it was difficult to distinguish exactly which set of teeth made which bites," Sheets said.
"That tells us that a single bite mark is not distinct enough to be linked to a specific individual. It can actually point to many different individuals," he said.
This means that a false identification is possible, which can lead a police investigation away from the real perpetrator and towards an innocent individual, researchers said.
