A study of multiple bitemarks inflicted in human skin by a single dentition using geometric morphometric analysis

Area of Science:

• Forensic science
• Dental identification
• Biometrics

Background:

• Bitemark analysis is a forensic discipline used for identification.
• Previous criticisms highlight the lack of scientific data on skin distortion in bitemarks.
• No systematic statistical studies have quantified the range of distortion in skin bitemarks.

Purpose of the Study:

• To scientifically investigate the range of distortion in human skin bitemarks.
• To compare the accuracy of bitemark impressions in skin versus wax and digital dental scans.
• To assess the reliability of bitemark analysis in forensic identification.

Main Methods:

• Created 89 bitemarks in human cadaver skin using a single dentition.
• Created wax impressions and obtained 2D scanned images of the same dentition.
• Utilized geometric morphometric methods, including Procrustes superimposition, to analyze landmark data from teeth and impressions.
• Compared bitemarks to the original dentition, wax impressions, and a database of 411 scanned dentitions.

Main Results:

• Measurement error was substantially lower for wax impressions and digital scans compared to skin bitemarks.
• None of the 89 skin bitemarks precisely matched the original dentition within error margins.
• In comparisons with a larger dentition database, the closest match to a bitemark was not always the producing dentition.
• Statistical analyses (PCA, CVA) showed clear segregation between skin bitemarks, wax impressions, and dentition shapes, indicating significant distortion.

Conclusions:

• Skin distortion significantly alters bitemark shape, affecting accuracy.
• Bitemark analysis may be unreliable, especially when multiple suspects have similar dentitions.
• Forensic bitemark identification requires a cautious approach due to unreliability.