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The controversial history of bite mark analysis

Crime Scene Investigation

In the late 1940s, the city of London was shaken by a series of unexplained disappearances. You might be surprised to learn that it was an oral appliance that finally brought the reign of terror to an end. John George Haigh, also known as the “Acid Bath Murderer,” had made every effort to eliminate evidence of his crimes. However, he missed the fact that his final victim had left behind a partial denture. Its discovery in his possession was instrumental in helping investigators identify the victim, leading to Haigh’s eventual arrest and conviction in 1949.

Dental remains are unique in their ability to be preserved almost indefinitely after death. The status of each person’s dentition is distinctive, as we saw in the aforementioned case, making these records a valuable way to identify remains if more standard forms of analysis and identification are not possible. Forensic odontology, more commonly known as forensic dentistry, is the application of dental science to the field of law. Forensic dentists fill a unique niche in the field of law enforcement and are responsible for managing dental records, identifying human remains, reporting signs of abuse and presenting dental evidence as an expert witness in legal cases.

Occasionally, forensic dentists study injuries caused by human bites to identify the persons involved. Use of bite mark evidence in the courtroom can be traced back to 1692, but it was wasn’t until 1984 that the American Board of Forensic Odontology established guidelines for bite mark analysis. Since then, this organization has expanded its workshops to standardize the way bite mark evidence is recovered, stored, analyzed and evaluated. Currently, bite mark evidence is recovered based on a written description, an examination of the victim and suspect, photography of the site of injury, saliva evidence, dental impressions and tissue samples. Use of 3D-scanning and other digital imaging methods are currently being researched, aimed at improving the accuracy of these analyses.

Such evidence is considered admissible in a court of law, but opinions on its validity and reliability have historically been highly controversial. There are multiple factors that can distort the accuracy of the bite mark, such inflammatory swelling of the skin, age of injury, aberrant muscle forces, and post-mortem tissue changes. Additionally, while bite mark analyses have resulted in positive identification for many legal cases, there are also a great number of instances where its use has resulted in misidentification. In 1989, a man named Steven Mark Chaney was convicted for murder and sentenced to life in prison based primarily on bite mark evidence and testimony given by a forensic dentist. However, it wasn’t until just this past fall that the the evidence was re-examined and found to be insufficient. After spending 28 years in prison, Chaney’s wrongful conviction was finally overturned.

Chaney’s case is but one of many that forensic experts are citing as a reason to reexamine the use of bite mark evidence in the courtroom. Following Chaney’s exoneration, the Texas Forensic Science Commission (TFSC) issued a moratorium on its use as evidence in criminal cases until reliability could be established with further research. In addition, the TFSC has decided to conduct an audit of all cases involving bite mark evidence.

The future of bite mark analysis is uncertain, but the development of the technology behind it will undoubtedly improve in the coming years. Yet, even among such uncertainty, a forensic dentist’s purpose remains clear: to bring justice to those who have been wronged and to bring closure to the families of those who have been lost.

~ Farnaz Hadaghian, predental

Farnaz Hadaghian

Farnaz graduated from Stony Brook University in 2015 with a B.S. in Biochemistry. She is presently working as a biology lab lecturer at SBU. In her spare time Farnaz volunteers in a research lab focusing on salivary gland stem cells. She plans on applying to dental school this summer.

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