猎枪射击弹壳痕迹检验

An Example of Examining the Shotshell Marks

在火台及火药气体压力的作用下,猎枪射击弹壳击针痕迹的底部多发生变形、凸起、开裂或击穿,其稳固性受到不同程度的破坏,给检验工作增加了不确定因素,可能误导检验者对击针头真实形态的认识而作出错误判断。本案通过比对检材与样本的击针痕底面特征和痕底边缘特征以及后膛痕迹,得出现场两枚弹壳分别为查获的唧筒式猎枪及立式双管猎枪的下枪管射击的结论。特别介绍了上枪管射击弹壳击针痕迹口部的擦痕,该痕迹是击针倾斜打击所致,属于初生痕迹而非次生的"舌痕",其价值除了可用于区分枪种、上(下)枪管外,还可用作定位基准及同一认定。

Frequently, the firing pin marks may be distorted, bulged, cracked or penetrated due to the pressure from the anvil and the gas of gunpowder. This may cause damage to the reproducibility of firing pin marks in different degrees, and may cause greater uncertainty to the examination and even misguide to a false judgment on the marks. In the case reported here, two shells from crime scene were collected and two types of suspected shotguns were recovered（one is a pump shotgun and another is a double-barrel（up and under one） shotgun）. By comparison of the marks on bottom and edge parts of the firing pin and those on the breech face, a conclusion was made that one shell was fired from the pump shotgun and the other from the double-barrel one. Specially, the scratch marks on the edge of the firing pin impression were introduced onto the shell that was fired from the up barrel of the double-barrel shotgun during the process of the firing pin tilting against the primer. These scratch marks are primary marks, different from the drag marks by the firing pin. With the scratch marks, not only can the type of shooting gun and even the barrel（up or under） be distinguished but the firearms can be identified as well.