The use of 3D-printed replicas of homicide weapons during autopsy.

A large percentage of homicides involve sharp or blunt weapons. Analyzing injuries and their mechanisms in such cases should include comparing the weapon with the injuries and evaluating the direction of impact(s). This is done typically through macroscopic observations, measurements, tool mark analysis or imaging techniques. Using replicas of weapons created via three-dimensional (3D) printing during autopsy can implement the application of these methods. Scaled photographs of weapons, routinely made during crime scene investigation, provide a perfect basis for 3D modelling. Three-dimensional objects such as hammers or axes, can be modeled with computer-aided design (CAD) software or 3D scanning methods like photogrammetry. Five case reports of homicides involving sharp or blunt weapons are presented to illustrate the routine application of 3D-printed replicas. The case reports illustrate how this technique can help demonstrate the mechanism, especially if combined with 3D reconstruction methods.