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Study Reveals Unreliability of Bitemark Analysis in Trials

New research, published in the Journal of the California Dental Association, highlights the lack of scientific support for bitemark analysis as evidence in trials. The study, which includes an analysis of existing literature and 12 new studies, suggests that this forensic science has led to wrongful convictions, including cases where individuals were sentenced to death.

Key Points

  • Lead author Mary Bush, Associate Professor at the State University of New York in Buffalo, emphasizes that the scientific community does not endorse the fundamental premises of bitemark analysis. She states, “The scientific community does not uphold the underlying premises that human teeth are unique and their unique features transfer to human skin.”
  • The research reveals that relying on bitemark transfer to identify perpetrators is unreliable. In a dataset of 1,100 individuals, even with just 25% distortion, a significant number of the population could potentially have created the bite.
  • The study’s findings serve as a cautionary tale about the dangers of relying on bitemark evidence in trials.

Wrongful Convictions and Exonerations

The case of Keith Allen Harward, who spent 33 years in prison for a crime he did not commit, illustrates the serious consequences of bitemark analysis. Harward’s conviction relied heavily on a bitemark found on the victim’s skin. Professor Bush explains, “Results from DNA testing proved that Harward could not have committed the crime, and the real perpetrator was identified. Harward was subsequently released from prison.”
– Another case highlighted in the study involves Eddie Lee Howard, a black man sentenced to death in 1994 based on bitemark evidence. After spending 26 years on death row, Howard was exonerated through new forensic opinions, powerful alibi witnesses, and DNA evidence. He was released from Mississippi’s death row in December 2020.

History and Recognition of Unreliability

The reliance on bitemark evidence stems, in part, from the conviction of serial killer Ted Bundy, who was mainly convicted based on bitemark evidence. The national attention given to Bundy’s trial in 1979 contributed to the prominence of bitemark evidence.

The authors’ findings align with prior studies, including a comprehensive report by the National Academy of Sciences (NAS). In 2009, the NAS released a report stating that there was no scientific basis for dentists to positively identify perpetrators by matching dental patterns to marks on victims’ bodies.

Additionally, a recent review by the U.S. National Institute of Standards and Technology (NIST) supports the study’s conclusions. The NIST review found a lack of support for the key premises of bitemark analysis, including the uniqueness of human dentition, accurate transfer of uniqueness to human skin, and reliable interpretation of identifying characteristics.

Raising Awareness and Implications

The authors aim to raise awareness of the unreliability of bitemark evidence by presenting their findings at national meetings and publishing in peer-reviewed journals. They emphasize the need to reconsider the use of bitemark analysis in trials and address the potential liabilities associated with testifying based on this type of evidence.




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