Mathematical matching of a dentition to bitemarks: use and evaluation of affine methods

Skin is a less than ideal medium for recording bitemark impressions, and assessing the causes and magnitude of distortion has long been a question in forensic odontology. Affine methods have been suggested as a mathematical means to attempt to quantify the deformation typically seen with a bitemark. Thirty-six bites were created on unembalmed human cadavers with a single dentition. Three mathematical affine methods were evaluated to determine if the distortion could be described mathematically and effectively removed. A measure of mismatch of a dentition to a bitemark was developed based on landmark measurements establishing a numerical basis for comparisons of dentitions to bitemarks. Results indicate high levels of distortion in the bitemarks not attributable to affine deformations or measurement error, suggesting that non-uniform anisotropic properties of skin mostly contribute to the distortion seen, thus concluding that bitemark distortion cannot be corrected by using affine transformations.