A comparison between direct and indirect methods available for human bite mark analysis

Comparison techniques used in bite mark analysis are many and varied, the choice of technique depending largely on personal preference. Until recently, no one technique has been shown to be better than the others, and very little research has been carried out to compare different methods. This study evaluates and compares the accuracy of direct comparisons between suspects' models and bite marks with indirect comparisons in the form of conventional traced overlays of suspects' models or a new method using photocopier-generated overlays. Artificial bite marks in pigskin were made using standardized sets of models and recorded as photographs and fingerprint powder lifts on tape. The bite mark photographs and fingerprint lifts were coded and randomized so that a blind comparison could be made with the models, traced overlays, and photocopier-generated overlays using a modified version of the American Board of Forensic Odontology Scoring (ABFO) System for Bite Marks. It was found that the photocopier-generated overlays were significantly more accurate at matching the correct bite mark to the correct models irrespective of whether the bite mark was recorded photographically or as a fingerprint lift. The photocopier-generated overlays were also found to be more sensitive at matching the correct bite marks to the correct models than the other two methods used. The modified ABFO scoring system was able to discriminate between a correct match and several incorrect matches by awarding a high score to the correct match.