Keyhole lesion caused by a fatal self inflicted headshot with a modified flare gun

In the following case report, we discuss the scene examination and autopsy results of an 86-year-old man who committed suicide in his closed garage by shooting himself in the head with a modified flare gun while seated in the passenger seat of his car. During the external examination of the autopsy an atypical injury on the scalp and skull showed the characteristics of both an entry and exit wound simultaneously, consistent with the phenomenon of a keyhole fracture. There are differing forensic interpretations regarding the mechanism of this fracture. One possible explanation is that it forms because of a tangential gunshot. In such cases, the kinetic energy of the bullet is transmitted to the bone surface at an oblique angle, combined with the pressure wave simultaneously affecting the calvaria and intracranial space, and secondary projectiles (bone fragments) contribute to the characteristics of this special injury as well. Other authors state that a keyhole fracture can also occur when the bullet strikes the bone perpendicularly. In our case, by comparing the findings from the scene investigation and the autopsy, it was determined that the keyhole fracture was a result of a tangentially directed shot. Moreover, considering the suicidal intent, the injury was found at an atypical location - the occipital part of the skull. Given the highly atypical injury location, injury pattern and firearm, we hope that the present case study will be of assistance to colleagues in the forensic evaluation of similar atypical gunshot injuries.