Accuracy of bite mark overlays: a comparison of five common methods to produce exemplars from a suspect's dentition

Physical comparison of a suspect's teeth to a bite mark injury using hollow volume comparison overlays is a common forensic odontology technique. Several methods are used to record characteristics of the size, shape and position of the teeth and to generate overlays. These include computer-based, radiographic, xerographic and hand-traced methods. Five common overlay production methods were compared using digital images of dental study casts as a reference standard. Area of the biting edges of the anterior teeth and relative rotation of each anterior tooth were measured and compared. The computer-based production method was determined to be the most accurate of those studied. It produced accurate representations of the biting edges of the teeth in an objective manner. The radiographic method was determined to be more accurate than the xerographic method with respect to tooth area measurement. The opposite is true with respect to tooth rotation. Hand-traced methods, from either wax impressions of teeth or directly from study casts, were determined to be inaccurate and subjective. It is recommended that forensic odontologists discontinue the use of hand-traced overlays in bite mark comparison cases.