Bite-Mark Analysis is Not Scientifically Valid and Leads to Wrongful Convictions

September 9, 2016 | Erica Tennenhouse

Photo credit: David Shankbone/Wikimedia (CC BY-SA 3.0)

New report is critical of pattern-matching forensics.

The President’s Council of Advisors on Science and Technology (PCAST) has produced a report condemning the use of forensic bite-mark matching to convict criminals.

According to The Intercept, which obtained a draft of the report prior to its public release, it states “available scientific evidence strongly suggests that examiners cannot consistently agree on whether an injury is a human bitemark and cannot identify the source of [a] bitemark with reasonable accuracy.”

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Forensic dentists analyze bite marks left on the flesh of victims or perpetrators after a violent attack, and the idea is that the impressions are unique enough to identify the biter. But as The Intercept explains, there is no science backing up the uniqueness of human bite marks, and the skin’s elasticity and propensity to heal means that markings in the skin will change shape over time.

Perhaps unsurprisingly, bite-mark analysis has led to more than two-dozen wrongful arrests or convictions to date.

The report states that although finding a way to scientifically validate bite-mark analysis would be the ideal solution, “PCAST considers the prospects of developing bitemark analysis into a scientifically valid method to be low.”

The report is generally critical of pattern-matching forensics, including shoe-print matching, firearms analysis, tool-mark analysis, and fingerprint matching, as these analyses are subjective and the observed patterns are not certain to be unique, according to The Washington Post.

But where pattern matching may be flawed, new promising forensic identification techniques are in the works. Just this week, a study demonstrating how unique protein markers in hair could be used in tandem with DNA for identification was published in PLOS ONE.

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