Investigating Fracture Morphology in Gunshot Trauma

As gunshot trauma becomes more prevalent in forensic anthropology casework, updated methods for the analysis and interpretation of gunshot trauma are needed. Skeletal trauma analysis has recently seen a shift in methodology from a morphological approach to a more biomechanically informed approach. Fractography, the study of how materials fracture and ultimately fail, has been recently applied as a framework for skeletal trauma analysis in forensic anthropology. Few fractographic studies have focused on gunshot trauma, however. This thesis adds to fractographic research on gunshot trauma through the examination of experimentally produced gunshot defects and their relationships to extrinsic variables including bullet kinetic energy, caliber, and firearm-to-target distance. This thesis examined experimentally generated gunshots in 30 pig (Sus scrofa) scapulae. Three different firearms were used – a .32 pistol (n = 10), a .40 pistol (n = 10), and a .308 rifle (n = 10) – to achieve a range of bullet kinetic energies. Experiments were performed from two distances: 0.1 meters (n = 15) and 1.1 meters (n = 15). Data was collected on number of radiating fractures, total fracture length, entrance diameter dimensions, exit diameter dimensions, entrance and exit symmetry, the number of crack branching points, and presence of cone cracks, and circumferential fractures. Results indicate that the number of radiating fractures, crack branching points, and total fracture length increases as the kinetic energy increases with statistically significant differences between the lowest (.32 pistol) and highest (.308 rifle) kinetic energy impacts. Statistically significant differences in the entrance defect dimensions were found between the .40 pistol and other two firearms, indicating that caliber influences defect size to an extent. Distance was not found to have a statistically significant effect on fracture morphology. This study provides baseline information about the relationships between bullet kinetic energy, caliber, distance, and several characteristics of fracture morphology. These results build upon current knowledge of gunshot trauma and can serve as a starting point for further investigations into the effect of kinetic energy, caliber, and distance on gunshot trauma morphology. Finally, this study demonstrates the utility of fractographic and quantitative approaches in studying gunshot trauma. Application of fractography allowed for the identification of features related to fracture initiation and propagation while quantitative data allowed for the testing of relationships between specific fracture characteristics and extrinsic factors. While this research focused on kinetic energy, further research should be conducted to investigate velocity and mass separately, as knowledge of their independent effects on fracture morphology will provide a more detailed understanding of fracture initiation and propagation in gunshot trauma.