Institute of Forensic Medicine, University of Zürich, Winterthurerstrasse 190/52, 8057, Zurich, Switzerland.
Department of Biotechnology and Biophysics, Julius-Maximilians-University Würzburg, Am Hubland, 97074, Würzburg, Germany.
Int J Legal Med. 2019 Jul;133(4):1115-1120. doi: 10.1007/s00414-018-1965-7. Epub 2018 Nov 14.
The pattern of gunshot residue (GSR) includes important information about muzzle-target distance since a larger GSR distribution diameter indicates a larger shooting distance. GSR may not be visible to the naked eye when, for example, it is located on dark textiles. In such cases, further procedures need to be performed in order to visualize the pattern of GSR. Besides chemical procedures, an alternative light source or infrared photography can be utilized for non-destructive GSR visualization. In the work presented, these two techniques are compared based on shooting experiments using 26 different dark textiles. Within the range of the alternative light source, the use of a 440-nm light in combination with an orange-colored filter led to the best visualization of GSR in the form of fluorescent particles. Infrared photography, on the other hand, visualized GSR as dark particles, whereas-ideally-the dark textile reflected the infrared light and appeared bright. The comparison of both techniques revealed that the GSR distribution visualized by infrared photography was not identical to the GSR distribution visualized with 440-nm illumination in combination with an orange-colored filter. We concluded that infrared photography visualizes the inner powder soot zone, whereas illumination at 440 nm leads to fluorescence of the outer powder soot zone, which can be visualized using an orange-colored filter. Knowledge of this difference in visualization of the two powder soot zones is important for forensic practitioners assessing firing distances. In the literature, however, this difference is not noted as clearly.
射击残留物（GSR）的分布模式包含有关枪口-目标距离的重要信息，因为较大的 GSR 分布直径表明射击距离较大。例如，当 GSR 位于深色纺织品上时，可能无法用肉眼看到。在这种情况下，需要进行进一步的程序才能观察到 GSR 的分布模式。除了化学程序外，还可以使用替代光源或红外摄影术对 GSR 进行非破坏性可视化。在本研究中，基于使用 26 种不同深色纺织品进行的射击实验，对这两种技术进行了比较。在替代光源的范围内，使用 440nm 光结合橙色滤光片导致 GSR 以荧光颗粒的形式得到最佳可视化。另一方面，红外摄影术将 GSR 可视化为暗颗粒，而理想情况下，深色纺织品会反射红外光并显得明亮。这两种技术的比较表明，红外摄影术可视化的 GSR 分布与 440nm 照明结合橙色滤光片可视化的 GSR 分布并不完全相同。我们得出结论，红外摄影术可视化内部粉末烟尘区，而 440nm 照明会导致外部粉末烟尘区的荧光，这可以使用橙色滤光片进行可视化。对于评估射击距离的法医从业人员来说，了解这两个粉末烟尘区的可视化差异非常重要。然而，在文献中，并没有如此明确地注意到这种可视化差异。
