Indirect fractures in long bones resulting from gunshot trauma: Occurrence, characterization, and need for additional research

Indirect fractures from gunshot wounds can occur when a projectile impacts soft tissue without making direct contact with the bone. Existing biomechanical and clinical research suggests that indirect fractures result in lower levels of comminution, and that resultant fracture patterns can resemble those seen in blunt force trauma (e.g., wedge-shape, oblique, transverse). In this paper, we document the occurrence, characterize fracture patterning, and highlight challenges in the analysis of indirect fractures using three independent sources of data: (1) forensic cases from the New Mexico Decedent Image Database (NMDID); (2) experimental data from gunshot trauma in animal bone; and (3) a survey of forensic practitioners on gunshot wound interpretation. Our analysis demonstrates that indirect fractures from gunshot trauma in long bones are indeed present in forensic casework, and that, in the absence of other lines of evidence (e.g., presence of defects on other bones, recovered bullet fragments, information about the scene), they are predominantly identified by analysts as resulting from non-gunshot mechanisms of injury. Indirect fractures therefore represent a significant challenge for interpreting the mechanisms and circumstances of injury, as they may be misclassified as blunt force trauma rather than gunshot related; this may produce incorrect conclusions impacting both the direction of the forensic investigation and type of prosecution. Research into the biomechanical conditions contributing to indirect fracture formation is therefore imperative to strengthen anthropological understanding of fracture morphological variability in gunshot trauma.