The National Institute of Standards and Technology (NIST) recently released a draft report questioning the scientific foundation of bitemark analysis, a widely used forensic technique. This technique involves comparing bite marks on a victim’s skin with the dental impressions of a suspected biter. The report, titled Bitemark Analysis: A NIST Scientific Foundation Review, highlights significant concerns regarding the accuracy, reliability, and validity of this forensic method.
Key Findings: Insufficient Scientific Foundation
According to the NIST review, bitemark analysis lacks a solid scientific basis because the three core premises underpinning the field are not supported by sufficient data:
- Non-unique Dental Patterns: The assumption that a person’s front teeth create a unique dental pattern has not been substantiated by studies. No large-scale population studies have been conducted to identify distinguishing features of human dentition. Additionally, no studies assess how common or rare such features are.
- Inconsistent Transfer of Dental Patterns to Skin: Bitemark analysis assumes that the pattern left by a bite is a direct and accurate representation of the biter’s dental features. However, the elasticity of human skin and potential victim movement during an attack distort these marks. Swelling, healing, and other factors further alter the pattern over time, making an accurate comparison difficult.
- Challenges in Analyzing Bitemarks: The report questions the ability of bitemark examiners to accurately analyze the marks left on a victim’s skin. Studies, including a 2016 report, showed that experts often disagreed on whether certain injuries were bitemarks. When they did agree, they could not consistently identify whether the marks were caused by adults, children, or animals.
Guidelines and Findings by the ABFO
Current guidelines from the American Board of Forensic Odontology (ABFO), the primary body representing bitemark examiners in the United States, allow three possible conclusions: “exclude,” “not exclude,” and “inconclusive.” An “exclude” finding means the suspect’s teeth could not have caused the bitemark, while a “not exclude” finding means it is possible that the suspect’s teeth could have made the mark. However, the draft report notes that these conclusions are drawn based on the unsupported premises of bitemark analysis.
Extensive Review and Expert Insights
The NIST draft report represents an exhaustive examination of more than 400 publications. It includes scientific articles, conference presentations, professional standards, and book chapters. The review was led by Kelly Sauerwein. She is a biological anthropologist at NIST. The review sought to determine the validity of bitemark analysis. It aimed to identify any existing knowledge gaps. Additionally, the review was informed by a 2019 meeting of forensic experts. Challenges and shortcomings in the field were discussed during this meeting.
Moving Forward: A Call for Research and Regulation
The NIST report is not intended to regulate forensic practices. It aims to guide forensic laboratories in making informed decisions about the methods they use. It also highlights the need for future research to address the identified gaps in the field of bitemark analysis.
Public Comment and Upcoming Webinar
The draft report will be open for public comment until December 12, 2022. This allows experts and the public to share feedback. They can do so before the final version is published. Additionally, NIST will host a webinar on October 27, 2022, to discuss the report and its findings. More details about submitting comments and webinar registration are available on the NIST website.
