Differentiation between bullet types by means of a 3D analysis of gunshot cavitation and bullet fragmentation - A computed tomography study in ballistic gelatine

Identification of the projectile type is among the main objectives in the forensic investigation of a gunshot incident, even if the projectile itself cannot be recovered. Medical imaging, primarily computed tomography (CT), has become a valuable tool in the examination and documentation of gunshot injuries. Bullet types often exhibit distinct patterns of fragment deposition and wound cavitation. In this study, we examined the potential of a CT-based digital three-dimensional (3D) analysis of cavitation and fragmentation patterns to distinguish between four bullets of.223 Remington ammunition (one soft point, one full metal jacket, and two expanding monolithic bullets). We utilized 20 x 20 x 25 cm blocks of ballistic gelatine as tissue simulant, with artificial skin on entry and exit walls of the blocks. Test firing was performed from a distance of 50 m. The gelatine blocks were CT-scanned and 3D reconstructions of the blocks, demonstrating both air cavitation and metal fragments, were generated. In addition, other parameters of cavitation and fragmentation were obtained from the CT scans, including the volume and internal surface area of the air cavity within the gelatine block. Entry and exit defects of the skin simulant were also documented. Our results indicated that different bullet types exhibited different cavitation and fragmentation patterns. We also detected differences in exit wounds in the skin simulant. Further studies are needed to confirm our preliminary findings that a digital 3D analysis may aid to distinguish the bullet type in certain forensic scenarios.