Institute of Forensic Medicine of the University of Bern, Murtenstrasse 26, 3008, Bern, Switzerland.
Criminal Investigation Service, Cantonal Police Department of Bern, Nordring 30, 3013, Bern, Switzerland.
Int J Legal Med. 2024 May;138(3):1149-1156. doi: 10.1007/s00414-023-03141-8. Epub 2023 Dec 13.
Biological traces inside firearm barrels were observed as a result of contact shots to the head. The present study was conducted to investigate the influence of the muzzle to target distance on staining inside the anterior and posterior part of firearm barrels. Ninety-nine shots were fired to so-called reference cubes (10% gelatine, 12 cm edge length, embedded paint-blood-pad) using three current handguns. Shot range was varied from contact to 50 cm distance. High-speed cameras recorded external backspatter. Endoscopic examination assessed visible staining along the barrel. Each two swabbings were gathered from the anterior and the posterior part of the barrel. The first swabs were submitted to quantitative PCR, the second ones to DNA-RNA-co-extraction. Thorough mechanical and chemical cleaning was performed to avoid any contamination which was controlled by negative zero swabs after each cleaning. In single shots up to 50 cm distance, minimal, but DNA-positive sporadic traces were detected inside the barrel in vicinity of the muzzle. Visible complex staining varying in extent was observed in the anterior barrel part for 10 cm or less distance in dependence of the calibre. The posterior part showed detectable traces only after close range shots (< 5 cm). Generally staining inside the barrel decreased from the muzzle to the rear end, which correlated with the yield of DNA. Some contact shots did not cause any staining in the posterior part of the barrel despite massive external backspatter. Blood-specific miRNA was primarily found where DNA was detected. This experience encourages to take a second swab for RNA analysis. The amount of nucleic acids in the barrel at varying muzzle to target distances is subject to large variations between individual shots and therefore appears not suitable for a reliable determination of the shot distance in a particular case on its own. Instead, shot range estimation should also take into account morphology and distribution of traces inside the barrel.
生物痕迹在枪管内被观察到是由于接触射击到头部。本研究旨在调查枪口到目标距离对枪支枪管前后部染色的影响。使用三把当前的手枪向所谓的参考立方（10%明胶，边长 12 厘米，嵌入油漆-血液-垫）发射了 99 发子弹。射击范围从接触到 50 厘米的距离不等。高速摄像机记录外部后喷。内窥镜检查评估了枪管上可见的染色。从前部和枪管的后部收集了每个两个拭子。第一个拭子用于定量 PCR，第二个用于 DNA-RNA 联合提取。进行了彻底的机械和化学清洁，以避免任何污染，每次清洁后用阴性零拭子进行控制。在 50 厘米距离内的单次射击中，在枪口附近的枪管内检测到最小但 DNA 阳性的零星痕迹。在距离枪口 10 厘米或更短的距离内，在前部枪管部分观察到可见的复杂染色，其程度取决于口径。在后部只有在近距离射击（<5 厘米）后才能检测到痕迹。总的来说，从枪口到后端，枪管内的染色减少，这与 DNA 的产量相关。尽管有大量的外部后喷，但有些接触射击并没有在枪管的后部造成任何染色。血液特异性 miRNA 主要在检测到 DNA 的地方发现。这种经验鼓励进行第二次拭子 RNA 分析。在不同枪口到目标距离的情况下，枪管中的核酸量在个体射击之间存在很大的差异，因此仅凭自身不太适合对特定情况下的射击距离进行可靠的确定。相反，射击范围的估计还应考虑到枪管内痕迹的形态和分布。
