Reverse engineering in forensic investigations: a new approach to bite mark analysis.

The study of bite marks provides crucial elements that contribute towards identifying the biter. In many cases, it assumes importance when bite marks are detected on the body of a victim of violence, but it could also be relevant when the bite marks are seen on food substances at the crime scene. In both circumstances, comparing the bite marks with a suspect's dentition can be decisive in confirming or excluding the culpability. In this case report, a bun (bread roll) with the sign of a bite was found at the crime scene. We report a pilot study using 3D reproduction of the bite mark on the bun and dental models of the alleged biter and the victim. A reverse engineering process was used to obtain digital 3D models of the bitten bun and the dental models by taking numerous photographs and stitching them together using a software called Metashape by Agisoft. The last step was to compare the bitemark to the two dental models, evaluating the spatial distance, the degree of overlap, and the degree of interpenetration. The results confirmed the usefulness of reverse engineering in forensic investigations showing the compatibility between the victim's teeth and the bite mark on the bun.

Reverse engineering techniques applied to a human skull, for CAD 3D reconstruction and physical replication by rapid prototyping.

The production of a copy of an existing object of complex shape is one of the typical applications of the integration between two modern computer-based technologies, reverse engineering (RE) and rapid prototyping (RP). The method is extremely versatile and can be used in various applicative domains (e.g. replacement of anatomical parts with artificial prostheses, replication of skeletal remains). Two different acquisition techniques of images of a skull, by laser and by CT scan, were compared to ascertain which enabled more accurate reproduction of the original specimen. The skull was chosen due to it being the body part most often used in medico-legal investigations (for personal identification, skull-photo superimposition techniques, forensic art, etc). Comparison between the copy and the original yielded satisfactory results for both techniques. However, CT scanning demonstrated some advantages over the laser technique, as it provided a cleaner point cloud, enabling shorter pre-reproduction processing times, as well as data on the internal parts, which resulted in the reproduction of a more faithful copy.