Seyfang Kelsey E, Kobus Hilton J, Popelka-Filcoff Rachel S, Plummer Andrew, Magee Charles W, Redman Kahlee E, Kirkbride K Paul
College of Science and Engineering, Flinders University, Sturt Road, Bedford Park, 5042 Adelaide, South Australia, Australia.
Forensic Services Branch, South Australia Police, South Australia 5000, Australia.
Forensic Sci Int. 2018 Dec;293:47-62. doi: 10.1016/j.forsciint.2018.10.017. Epub 2018 Oct 29.
The majority of 0.22 calibre rimfire ammunition available in Australia, and overseas, tends to use glass powder rather than antimony sulfide frictionator in the primer. This glass can be the nucleus of a GSR particle, with other primer components condensing around and onto the glass structure. As the composition of glass frictionator remains largely unaltered during ammunition discharge [1] there is the possibility that frictionator composition could be used in GSR examinations to either correlate or discriminate between samples, thereby providing valuable information to an investigation. In this study, the composition of glass frictionator from a wide variety of ammunition was analysed by time-of-flight - secondary ion mass spectrometry (ToF-SIMS), sensitive high-resolution ion microprobe (SHRIMP) and scanning electron microscopy - energy dispersive X-ray spectrometry (SEM-EDS). Refractive index (RI) was measured using glass refractive index measurement (GRIM). Across the population of ammunition studied, it was found that the elemental and isotopic composition of frictionator varied. ToF-SIMS was able to discriminate 94.1% of brands in a pairwise comparison and SEM-EDS achieved a pairwise discrimination power of 79.4%. If SHRIMP was combined with the other two techniques, 95.6% of brands could be discriminated. Refractive index measurements supported the elemental data showing that there appeared, in most cases, to be only one population of glass within a cartridge. The results suggest that there is scope for frictionator analysis to contribute valuable, new capability to forensic GSR examinations.
在澳大利亚及海外，市面上大多数0.22口径边缘发火式弹药倾向于在底火中使用玻璃粉而非硫化锑摩擦剂。这种玻璃可能成为枪击残留物（GSR）颗粒的核心，其他底火成分会围绕并附着在玻璃结构上。由于在弹药发射过程中玻璃摩擦剂的成分基本保持不变[1]，因此有可能在GSR检验中利用摩擦剂成分来关联或区分不同样本，从而为调查提供有价值的信息。在本研究中，采用飞行时间二次离子质谱（ToF-SIMS）、灵敏高分辨率离子微探针（SHRIMP）以及扫描电子显微镜-能量色散X射线光谱法（SEM-EDS）对多种弹药的玻璃摩擦剂成分进行了分析。使用玻璃折射率测量仪（GRIM）测量了折射率（RI）。在所研究的弹药群体中，发现摩擦剂的元素和同位素组成存在差异。在两两比较中，ToF-SIMS能够区分94.1%的品牌，SEM-EDS的两两区分能力达到79.4%。如果将SHRIMP与其他两种技术结合使用，则可以区分95.6%的品牌。折射率测量结果支持了元素数据，表明在大多数情况下，弹药筒内似乎只有一种玻璃。结果表明，摩擦剂分析有潜力为法医GSR检验提供有价值的新能力。
