Bite Mark Testimony Comes under Fire Yet Again


By Andrew Z. Giacalone

The practice of using bite marks to secure convictions in the court of law is coming under increasing scrutiny following a series of wrongful convictions based almost entirely on the unreliable and “controversial” practice, according to an article in

Texas Monthly


“The truth is, there was never any conclusive data or rigorous studies to back up bite mark evidence, which has been under fire from scientists and defense lawyers ever since it was first allowed in court in 1974,” says the Austin-based publication, noting that forensic odontologists—or forensic dentists—“sometimes can’t even agree” on whether marks found on skin come from teeth or not.


Texas Monthly’s

article on what is regarded as unreliable forensic science by the Innocence Project and the National Academy of Sciences, comes on the heels of the release of Steven Mark Chaney—a Dallas man who had his 1987 murder conviction reversed by a court last week due to discredited bite mark testimony. Chaney was convicted of the murder of John Sweek based largely on the testimony of two forensic dentists who claimed that his teeth matched to a mark on Sweek’s body. As a result, Chaney spent 28 years in prison for a crime he did not commit.

Nevertheless, testimony from forensic dentists who inspect the injuries of victims and attempt to match them to the dental patterns of alleged perpetrators has long been admissible in court and is often the prosecutor’s only physical evidence, reports the

Texas Monthly

. Jurors are often confronted with bite mark testimony and the forensic experts who tout it as full-proof even though a 2009 report issued by the National Academy of Sciences confirmed that “the scientific basis is insufficient to conclude that bite mark comparisons can result in a conclusive match.” This discredited practice has contributed to sending innocent people to prison. According to

Texas Monthly

, when asked why he voted to convict Chaney, one juror admitted: “The bite mark.”

Beyond Chaney’s wrongful conviction, however, the article observes that bite mark evidence was also used in Texas’ wrongful convictions of Calvin Washington and Joe Sidney Williams— two co-defendants in a 1987 rape and murder case—as well as the wrongful conviction of David Spence in his tragic death penalty case two years earlier. It adds that in both cases, the effect of the forensic dentist’s testimony on the jury was “powerful.”

The dubious credibility of bite mark evidence and its use in Chaney’s wrongful conviction has prompted his lawyers to ask the Texas Forensic Science Commission to “go back and vet” cases where bite mark testimony was used across the state. When it does so, the

Texas Monthly

warns, the commission will “almost certainly” find other “troublesome” cases.

According to Chris Fabricant, director of strategic litigation at the Innocence Project and one of Chaney’s attorneys:

Mr. Chaney’s case and the 25 other known wrongful convictions and indictments based on bite mark analysis, including at least two capital cases, demonstrates the public safety risk the continued use this forensic technique poses, and the urgent need to revisit cases that have relied on this evidence to secure convictions.  There is no basic or applied research supporting any of the assumptions of bite mark analysis, which has nonetheless been passed off as “scientific” evidence for decades, leading to these unconscionable, yet preventable, miscarriages of justice.”



for the Texas Monthly story.

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