The Cautionary Instruction: Bite mark analysis devoured by the courts

Matthew T. Mangino
Pittsburgh Post-Gazette/Ipso Facto
June 21, 2013

At least 24 men convicted or charged with murder, or rape, based on bite marks on the flesh of victims have been exonerated since 2000, many after spending considerable time in prison.

A small, mostly ungoverned, group of dentists carries out bite mark analysis, and the findings are often key evidence in prosecutions -- even though there is no scientific proof that teeth can be matched definitively to a bite into human skin.

The FBI doesn't use it, and the American Dental Association does not recognize it.

"Bite mark evidence is the poster child of unreliable forensic science," Chris Fabricant, director of strategic litigation at the New York-based Innocence Project told the Associated Press.

One notable case of faulty bite mark analysis involved a Pennsylvania native convicted in Arizona.

Ray Krone, the so-called "Snaggletooth Killer," was convicted in 1992, and after winning a new trial was convicted again in 1996, of the murder of a Phoenix woman. Krone’s conviction was based principally on bite mark identification. He was exonerated in 2002 after spending 10 years in prison, three on death row.

In 2004, I participated in a forum on the death penalty with Krone at Albright College in Reading, Pennsylvania. His case is a tragic example of forensic science run amok.

As far back as 1985 researchers were questioning the reliability of bite mark science, “There is effectively no valid documented scientific data to support the hypothesis that bite marks are demonstrably unique,” suggested a report at the time.

Twenty-eight years later the criticism has only increased. In 2009, the National Research Council found that there is “no science on the reproducibility of the different methods of analysis” of bite marks. The report concluded, “Different experts provide widely differing results.”

Now, a case in California may further impact the use of bite mark analysis in criminal trials.

In 1997, William Richards was convicted of murdering his wife -- two previous trials resulted in hung juries. Dr. Norman Sperber a top forensic dentist certified by the American Board of Forensic Odontology, testified during trial that a suspected bite mark on the victim’s body was consistent with a rare abnormality in Richards' teeth.

During an evidentiary hearing in 2009, Sperber recanted his testimony and said he had been wrong. The court reversed Richards' conviction, finding that the evidence “points unerringly to innocence." Prosecutors appealed, and the California Court of Appeals ordered Richards to remain in prison pending the outcome.

Richards’ appeal is still pending and appears to mark yet another setback for Forensic Odontology. Some “experts” in the field now argue that bite marks are best used to exclude suspects, not identify them.

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