Department of Forensic Medicine, University of Helsinki, P.O. Box 21, FI-00014, Helsinki, Finland.
Forensic Medicine Unit, Finnish Institute for Health and Welfare, P.O. Box 30, FI-00271, Helsinki, Finland.
Int J Legal Med. 2024 Mar;138(2):671-676. doi: 10.1007/s00414-023-03062-6. Epub 2023 Jul 17.
Computed tomography (CT) may have a crucial role in the forensic documentation and analysis of firearm injuries. The aim of this forensic ballistics case study was to explore whether two types of expanding bullets and a full metal-jacketed bullet could be differentiated by inspecting bullet fragments and fragmentation pattern in CT. Three types of .30 caliber bullets (full metal-jacketed Norma Jaktmatch, expanding full-copper Norma Ecostrike, and expanding soft-point Norma Oryx) were test fired from a distance of 5 m to blocks of 10% ballistic gelatine. CT scans of the blocks were obtained with clinical equipment and metal artifact reduction. Radiopaque fragments were identified and fragmentation parameters were obtained from the scans (total number of fragments, maximum diameter of the largest fragment, distance between entrance and the closest fragment, length of the fragment cloud, and maximum diameters of the fragment cloud). The fragmentation patterns were additionally visualized by means of 3D reconstruction. In CT, the bullet types differed in several fragmentation parameters. While the expanding full-copper bullet Ecostrike left behind only a single fragment near the end of the bullet channel, the soft-point Oryx had hundreds of fragments deposited throughout the channel. For both expanding bullets Ecostrike and Oryx, the fragments were clearly smaller than those left behind by the full metal-jacketed Jaktmatch. This was surprising as the full metal-jacketed bullet was expected to remain intact. The fragment cloud of Jaktmatch had similar mediolateral and superoinferior diameters to that of Oryx; however, fragments were deposited in the second half of the gelatine block, and not throughout the block. This case study provides a basis and potential methodology for further experiments. The findings are expected to benefit forensic practitioners with limited background information on gunshot injury cases, for example, those that involve several potential firearms or atypical gunshot wounds. The findings may prove beneficial for both human and wildlife forensics.
计算机断层扫描（CT）在法医记录和分析枪击伤方面可能具有重要作用。本项法医学弹道学案例研究旨在探讨在 CT 下检查子弹碎片和碎裂模式是否可以区分两种类型的扩张型子弹和全金属被甲弹。从距离 5 米处向 10%的弹道凝胶块测试发射了三种类型的.30 口径子弹（全金属被甲 Norma Jaktmatch、扩张型全铜 Norma Ecostrike 和扩张型软尖 Norma Oryx）。使用临床设备和金属伪影减少技术对凝胶块进行 CT 扫描。识别不透射线的碎片，并从扫描中获取碎裂参数（碎片总数、最大碎片直径、入口和最近碎片之间的距离、碎片云长度和碎片云最大直径）。通过 3D 重建进一步可视化碎裂模式。在 CT 中，子弹类型在几个碎裂参数上存在差异。扩张型全铜子弹 Ecostrike 在子弹通道末端仅留下单个碎片，而软尖 Oryx 则在整个通道中沉积了数百个碎片。对于扩张型子弹 Ecostrike 和 Oryx，碎片明显小于全金属被甲 Jaktmatch 留下的碎片。这令人惊讶，因为预计全金属被甲子弹会保持完整。Jaktmatch 的碎片云与 Oryx 的碎片云具有相似的内外径；然而，碎片沉积在凝胶块的后半部分，而不是整个块中。本案例研究为进一步实验提供了基础和潜在的方法。对于背景信息有限的枪击伤案例，例如涉及多种潜在枪支或非典型枪击伤的案例，研究结果有望为法医从业人员带来益处。研究结果可能对人类和野生动物法医学都有益。
