The punched-out tissue complex (skin-bone "imprimatum") in shots from captive-bolt guns: does it act as a secondary projectile?

From the first half of the twentieth century to the present day, injuries and fatalities from captive-bolt livestock stunners are a major topic in forensic medicine. The vast majority of cases account for suicides with the frontal, temporal, parietal, and occipital regions being the most common sites of entrance (in descending order of frequency). Due to the limited length of the bolt, the corresponding wound channel within the braincase is only several centimeters long. It has been a controversial subject for a long time, whether the skin-bone complex punched out by the conically grooved end of the steel rod may act as a "secondary projectile" being propelled beyond the actual path of the bolt. To answer this question, experimental shots from various types of captive bolt-guns were fired to simulants. Video-documentation employing a high-speed motion camera showed that the punched-out pieces of skin and bone did not move further than the bolt. Thus, a secondary extension of the total wound channel could not be observed. However, the suction effect caused by the bolt's rearward movement may induce a slight retrograde displacement of the skin-bone complex.