Abstract
An evaluation of the stabbing intensity including the degree of force necessary to cause a particular injury is a common task for forensic pathologists in court. Biomechanical analyses are essential for collecting objective data, serving as a baseline comparison among the highly individual circumstances of each case. However, previous investigations have utilized instruments only resembling the murder weapons as well as tissues from individuals other than the victim, including animal tissues or substitutes, which limits their applicability to forensic casework. In this study, a homicidal head stab case is presented, in which the blade penetrated over its full width, crossing the midline and injuring the brainstem and the contralateral hemisphere. A skull sample from the victim's contralateral side corresponding to the injured region was retrieved during the autopsy. For the stabbing experiments, a pendulum setup incorporating the original blade was employed. Three consecutive stabs were executed on the bone sample of the victim obtained at autopsy. Additionally, two other skull samples from different cadavers were each subjected to a single stab. The stabbings were performed at varying bone thicknesses (3-8 mm) and momenta (3.1-13.4 Ns) to account for mild, moderate, and strong impacts. High impact velocities resulted in either a blade entry across its full width, resembling the homicide case, or a multi-fragmental destruction of the bone. Mild and moderate impacts were insufficient to achieve full-thickness penetration of the skull. When stabbings were performed on a considerably thicker skull sample than that involved in the homicide case, only the blade tip penetrated the bone without achieving full-thickness perforation. By utilizing tissue from the victim and the real weapon for biomechanical analysis of the stabbing intensity including the minimum degree of force and momenta in homicidal stab cases, this experimental setup closely mimics the conditions of the actual case. Forensic investigators should proactively recommend such biomechanical analyses and secure appropriate tissue samples during autopsy to obtain objective experimental data relevant to legal questions.