A bullet striking the vault tangentially produces an irregular opening, termed a "keyhole defect," with the circular portion of the defect being the initial point of impact. The irregular morphology produced by a tangential bullet trajectory may be confusing. The wound itself exhibits characteristics of both gunshot entrance and exit wound trauma. Thus, a cursory examination of soft tissue around a tangential wound may be misinterpreted as an exit wound. The key to the accurate interpretation of gunshot trauma, especially in complex cases, lies in the complete recovery of bone fragments at the crime scene and at autopsy and an accurate reconstruction of the bone in question. A gross examination of the reconstructed specimen may be enhanced by low-power magnification and radiology. Fractured margins should be closely examined for crushing, fragments of metal, or metal streaking indicating evidence of the bullet impact site. Tubular bone exhibiting keyhole defects is useful in determining bullet direction and more useful in determining body position. 6 figures and 7 references