Schyma Christian, Lux Constantin, Madea Burkhard, Courts Cornelius
Institute of Forensic Medicine, University of Bern, Bern, Switzerland,
Int J Legal Med. 2015 Sep;129(5):1027-33. doi: 10.1007/s00414-015-1151-0. Epub 2015 Jan 24.
In practical forensic casework, backspatter recovered from shooters' hands can be an indicator of self-inflicted gunshot wounds to the head. In such cases, backspatter retrieved from inside the barrel indicates that the weapon found at the death scene was involved in causing the injury to the head. However, systematic research on the aspects conditioning presence, amount and specific patterns of backspatter is lacking so far. Herein, a new concept of backspatter investigation is presented, comprising staining technique, weapon and target medium: the 'triple contrast method' was developed, tested and is introduced for experimental backspatter analysis. First, mixtures of various proportions of acrylic paint for optical detection, barium sulphate for radiocontrast imaging in computed tomography and fresh human blood for PCR-based DNA profiling were generated (triple mixture) and tested for DNA quantification and short tandem repeat (STR) typing success. All tested mixtures yielded sufficient DNA that produced full STR profiles suitable for forensic identification. Then, for backspatter analysis, sealed foil bags containing the triple mixture were attached to plastic bottles filled with 10% ballistic gelatine and covered by a 2-3-mm layer of silicone. To simulate backspatter, close contact shots were fired at these models. Endoscopy of the barrel inside revealed coloured backspatter containing typable DNA and radiographic imaging showed a contrasted bullet path in the gelatine. Cross sections of the gelatine core exhibited cracks and fissures stained by the acrylic paint facilitating wound ballistic analysis.
在实际法医案件工作中，从枪手手上回收的逆向飞溅物可能是头部自伤枪伤的一个指标。在这类案件中，从枪管内部回收的逆向飞溅物表明在死亡现场发现的武器与头部受伤有关。然而，到目前为止，缺乏对影响逆向飞溅物的存在、数量和特定模式的因素进行系统研究。在此，提出了一种逆向飞溅物调查的新概念，包括染色技术、武器和目标介质：开发、测试并引入了“三重对比法”用于实验性逆向飞溅物分析。首先，制备了不同比例的用于光学检测的丙烯酸漆、用于计算机断层扫描中放射性对比成像的硫酸钡和用于基于聚合酶链反应的DNA分型的新鲜人血的混合物（三重混合物），并对其进行DNA定量和短串联重复序列（STR）分型成功率测试。所有测试混合物都产生了足够的DNA，生成了适合法医鉴定的完整STR图谱。然后，为了进行逆向飞溅物分析，将装有三重混合物的密封箔袋附着在装满10%弹道明胶的塑料瓶上，并用2 - 3毫米厚的硅胶覆盖。为了模拟逆向飞溅物，对这些模型进行近距离射击。对枪管内部进行内窥镜检查发现含有可分型DNA的有色逆向飞溅物，射线成像显示明胶中有对比明显的子弹路径。明胶核心的横截面显示出被丙烯酸漆染色的裂缝，便于进行伤口弹道分析。
