Bite marks have been used for decades by forensic scientists in criminal cases to help establish the identity of offenders.
But the fact it is a tried and tested method, does not mean it’s a reliable one. Now Texas is leading the way in developing guidelines on whether this evidence should be admissible at all in criminal cases.
A number of exonerations in Texas have raised serious questions over bite mark forensics.
Recently, the Dallas Morning News reported how Steven Mark Chaney, was released from prison in October after 28 years. Forensic dentists argued before the Texas Forensic Science Commission, whether bite patterns on the skin of a victim on a murder, rape and child abuse case can provide accurate clues to the perpetrator’s identity.
Chaney received a life sentence in 1987 on murder charges after a dental expert testified before a court that it was virtually certain that his teeth caused bite marks on an arm of the drug dealer victim of the crime who was stabbed to death. The New York Times reported on how the same expert has now said his testimony was unfounded. “Chaney is one of more than a dozen people around the country who have been released or exonerated in cases involving bite-mark testimony that was later debunked,” stated the New York Times.
Texas Forensic Science Commission is now seeking to develop guidelines on whether bite-mark comparisons should play a role of any description in the courtroom.
The New York Times reported this is just the latest example of the “turmoil” surrounding a number of types of evidence that are becoming discredited. Those involved in criminal justice are questioning evidence that has been used for some time, like handwriting analysis and microscopic hair comparisons, methods that are “based more on tradition than science.”
Scientists even say methods such as fingerprinting and some kinds of DNA matches are not nearly as foolproof as many once believed.
Bite mark evidence became famous during the televised trial Ted Bundy in 1979 but it’s now under fire.
The Texas agency is leading the way in the re-examination of forensic methods and testimony. “Some aspects of forensic science have never been validated,” said Vincent Di Maio, a medical examiner and retired doctor and who has been chairman of the Texas commission since 2012. “That’s a problem that had to be addressed, and nobody else was going to do it for us.”
Nationally forensic testing is increasingly under scrutiny. Earlier this year, the FBI informed crime labs across the country that investigators had discovered laboratories were using outdated protocols to interpret DNA results,
The issue meant some prosecutors were overstating the reliability of DNA evidence in court, which is often presented as accurate to within a fraction of a percent in cases.
A report issued in 2009 by the National Academy of Sciences, “Strengthening Forensic Science in the United States,” proved to be a turning point. An expert panel warned of massive disparities around the country both in the quality of crime laboratories and stated many methods had not been scientifically validated.