Karger B, Hoekstra A, Schmidt P F
Institute for Legal Medicine, University of Münster, Germany.
Int J Legal Med. 2001 Aug;115(1):16-22. doi: 10.1007/s004140000202.
Contact of a fired bullet with an intermediate target of sufficient resistance commonly causes the bullet to ricochet, fragment or perforate together with a deviation in trajectory. The transfer of intermediate target material to bullets and subsequent detection on the bullet surface after recovery from a bullet collector, were examined using a scanning electron microscope and an energy-dispersive X-ray spectrometer (SEM/EDS). A total of 76 gunshots (9 mm Luger FMJ RN bullets) were fired at various intermediate targets and at combinations of intermediate targets and tissue located in line. Elements already present on unfired bullets and elements from the bullet collector, the jacket, the charge and primer could be consistently detected as a "background". Abundant deposits of "fragile" (brittle) materials such as concrete, flat glass, asphalt and gypsum board could be visualised on every bullet by SEM. The transfer dynamics involved a direct imprint of target material on the bullet surface and thus preferential locations at the tip but also indirect deposition over the entire surface ("powder effect"). X-ray microanalysis demonstrated matching spectra of the elemental composition of these deposits and of the targets contacted. After perforation of "ductile" (flexible) materials such as wood and car body parts, the deposits on the bullets did not show characteristic spectra. If multi-layered car metal targets were hit, few and uncharacteristic fragments were scattered over the bullet surface and titanium indicative of paint-work could be determined on only a minority of bullets. The elemental composition of wood itself was heterogeneous but the fibrous morphology of the deposits was typical. The SEM/EDS findings in gunshots including subsequent perforation of tissue were similar. In particular, the trace evidence primarily transferred to the bullets was not eliminated by secondary contact and the determination of the fragile target materials was not affected. So when a person is killed or injured by a gunshot, the presence of a ricochet and the target material can be determined. This possibility needs to be considered before an evidential bullet is cleaned or contaminated.
发射的子弹与具有足够阻力的中间目标接触通常会导致子弹发生跳弹、破碎或穿孔，并伴有弹道偏差。使用扫描电子显微镜和能量色散X射线光谱仪（SEM/EDS）检查了中间目标材料转移到子弹上以及从子弹收集器回收后在子弹表面的后续检测情况。总共向各种中间目标以及位于同一直线上的中间目标与组织的组合发射了76发子弹（9毫米鲁格全金属被甲圆头子弹）。未发射子弹上已存在的元素以及来自子弹收集器、弹壳、装药和底火的元素可以作为“背景”被一致检测到。通过扫描电子显微镜可以在每颗子弹上看到大量“易碎”（脆性）材料的沉积物，如混凝土、平板玻璃、沥青和石膏板。转移动力学涉及目标材料在子弹表面的直接印记，因此在尖端有优先位置，但也有在整个表面的间接沉积（“粉末效应”）。X射线微分析表明，这些沉积物的元素组成与所接触目标的光谱相匹配。在穿透“韧性”（柔性）材料，如木材和汽车车身部件后，子弹上的沉积物没有显示出特征光谱。如果击中多层汽车金属目标，很少有且无特征的碎片散落在子弹表面，只有少数子弹上能确定指示漆面的钛元素。木材本身的元素组成是不均匀的，但沉积物的纤维形态是典型的。包括随后穿透组织的枪击事件中的扫描电子显微镜/能量色散X射线光谱仪结果相似。特别是，主要转移到子弹上的微量证据不会因二次接触而消除，并且对易碎目标材料的测定也不受影响。因此，当一个人被枪击中致死或受伤时，可以确定是否存在跳弹以及目标材料。在清洗或污染作为证据的子弹之前，需要考虑这种可能性。
