Transfer and Distribution of Gunshot Residue through Glass Windows

Research into the deposition patterns of primer gunshot residue (GSR) beyond a primary target was previously nonexistent. This study aimed to determine the deposition patterns of GSR once a bullet passed through an initial target and continued on its path into additional targets. Multiple repetitions were performed to assess the GSR deposition patterns after a bullet was shot through a closed window into either a dummy or a wall within an enclosed room. Samples were taken from both the primary and secondary target holes as well as from nontarget areas. Significant amounts of GSR were found on all samples. The results show that GSR continues to be deposited along the path of the bullet after passing through a primary glass target. These findings reiterate the lack of probative value in collecting GSR samples from gunshot victims even if they are in an enclosed area separate from the shooter.     

Validation of Toolmark Comparisons Made At Different Vertical and Horizontal Angles

Numerous studies have focused on determining whether objective statistical methods can be used to discriminate between known matches and nonmatches when comparing laboratory prepared toolmarks. This study involved an analysis of striated toolmarks made as a function of varying vertical and horizontal angles of attack. Comparisons based on experimental data show that replicate toolmarks from the same tool show high correlation values at identical vertical and horizontal angles, with the correlation decreasing as the angular difference increases, especially for horizontal angular changes. Comparisons between nonmatching samples produce low correlation values that remain unchanged as horizontal angular differences increase. While complete statistical separation was not achieved between matching and nonmatching samples, there is evidence demonstrating that toolmarks can be identified if the variation in horizontal angle is within 10°. The experiment shows that computer‐aided comparison techniques could be viable for identification with the proper statistical algorithm.     

微波消解-扫描电镜联用检测脏器内硅藻

目的介绍一种微波消解-扫描电镜联用检测脏器内硅藻的新方法。方法大白兔30只,随机分为生前溺死组（n=15）和死后溺尸组（n=15）。提取兔肺、肝、肾、股骨骨髓和现场珠江水样,采用建立的微波消解-扫描电镜联用法检测脏器组织和水样中的硅藻,并与硝酸乙醇消解-扫描电镜联用的方法进行比较。结果生前溺死组的兔肺、肝、肾、股骨骨髓组织中大多数观测到与现场珠江水样一致的硅藻,微波消解-扫描电镜联用法检测脏器内硅藻的平均含量分别为：2505.2个/2g肺,18.7个/10g肝,6.5个/10g肾,6.3个/0.5g骨髓;肺与肝、肾、骨髓检出硅藻的阳性比例为86.7%,脏器硅藻检出含量和硅藻检验阳性比例均明显高于硝酸乙醇消解-扫描电镜联用法所测值。死后溺尸组的兔脏器组织均未观测到硅藻。结论微波消解-扫描电镜联用法检测脏器内硅藻,高效、安全、环保,硅藻检验灵敏度高,降低了劳动强度,提高了定性定量分析准确度,且能有效避免污染,在法医学溺死鉴定中具有良好的应用价值。     

Detection of Gunshot Residue in Blowfly Larvae and Decomposing Porcine Tissue Using Inductively Coupled Plasma Mass Spectrometry (ICP‐MS)*

Abstract: Blowfly larvae and porcine tissue contaminated with gunshot residue (GSR) were collected during summer and winter months, over a 37‐day and a 60‐day sampling period, respectively. Wound samples were microwave‐digested and analyzed by inductively coupled plasma mass spectrometry (ICP‐MS) for the detection of antimony, barium, and lead. During summer, the 37‐day sampling period encompassed all stages of decomposition, except skeletonization. The three elements were detected in larvae only on days 3 and 4 after death but were detected at significant levels in tissue samples throughout the entire sampling period. In winter, no significant decomposition was observed throughout the 60‐day sampling. Although temperatures were too low for blowfly activity, the three elements were detected in the tissue samples at relatively constant, significant levels. Hence, GSR determination in tissue was more dependent on decomposition stage rather than time since death.     

Automated SEM/EDS Analysis of Airbag Residue. II: Airbag Residue as a Source of Percussion Primer Residue Particles

Abstract:  Automated scanning electron microscopy with energy dispersive spectroscopy has been used to analyze airbag residue particles. Analysis of airbag residue from some passenger side airbags revealed some residue particles which are consistent with gunshot residue (GSR) samples. The source of these particles was determined to be percussion primers used to initiate the chemical reaction for deployment. This article identifies some vehicles which contain this type of airbag and demonstrates the types of particles which could be misidentified as being GSR. The low numbers of GSR particles in among the large particle populations of zirconium and/or copper–cobalt particles, which are clearly airbag residue, allow the trained analysts to distinguish the correct source of this residue. Particles containing high aluminum levels, elevated levels of allowable elements in GSR particles, or the presence of elements that are rare in GSR particles stand out as indications that the particles are not GSR in origin. This study serves as a guide to analysts who perform particle analysis in forensic investigations.     

绵羊肺泡毛细血管的扫描电镜观察

运用血管铸型和扫描电镜技术对绵羊肺实质内微血管的构筑特征进行了观察,旨在揭示绵羊肺泡毛细血管的分布特征,为哺乳动物肺微血管的研究积累资料,并为牦牛肺微血管的进一步研究奠定基础。观察结果显示,低倍镜下,在截面上可见肺实质内的微血管网均呈大小不等的蜂窝状结构,肺泡囊和肺泡的轮廓清晰可见;高倍镜下肺泡毛细血管网呈网络状,视野内大部分肺泡毛细血管网伸展良好。经与文献中有关动物肺泡毛细血管的研究结果相比较,本试验中绵羊肺泡毛细血管的构筑特征与新生牦牛、双峰驼相近,而与人、犬、猴、兔、鼠等动物差别较大。     

用SEM观察真皮浅层微小刺伤的研究

本文报道了一种用酶水解表皮与真皮的连接,然后用扫描电镜观察微小损伤在真皮乳头层的损伤特点的新方法。研究结果表明,这种方法有利于微小刺伤的鉴定,并提供一些具体的鉴定指标。     

Fast gas chromatography of explosive compounds using a pulsed-discharge electron capture detector

The detection of a mixture of nine explosive compounds, including nitrate esters, nitroaromatics, and a nitramine in less than 140 sec is described. The new method employs a commercially available pulsed-discharge electron capture detector (PDECD) coupled with a microbore capillary gas chromatography (GC) column in a standard GC oven to achieve on-column detection limits between 5 and 72 fg for the nine explosives studied. The PDECD has the benefit that it uses a pulsed plasma to generate the standing electron current instead of a radioactive source. The fast separation time limits on-column degradation of the thermally labile compounds and decreases the peak widths, which results in larger peak intensities and a concomitant improvement in detection limits. The combination of short analysis time and low detection limits make this method a potential candidate for screening large numbers of samples that have been prepared using techniques such as liquid-liquid extraction or solid-phase microextraction.     

毒鼠强中毒实质性器官组织超微病理变化研究

目的观察不同浓度毒鼠强中毒大鼠实质性器官的超微病理变化。方法采用灌胃方法使大鼠毒鼠强染毒,制作大鼠中毒模型,并以健康大鼠灌服生理盐水为对照,提取大鼠的脑皮质、脑干桥脑部、心、肝、脾、肾等实质性器官,进行超微病理观察。结果不同浓度的毒鼠强可对心肌细胞、脑神经细胞、神经纤维和肝细胞造成一定损伤,而对肾、脾组织细胞损伤不明显。脑皮质神经元细胞结构模糊,内质网轻度扩张,线粒体扩张水肿,且无明显的剂量-反应关系;脑干桥脑部可见多处弥散性软化灶,神经细胞核溶解,神经纤维细胞有坏死,血管内皮细胞肿胀,血管周围有间隙出现,脑干损伤有明显的剂量-反应关系;心肌细胞表现为不同程度的心肌细胞坏死、线粒体弥漫性崩解或肿胀、肌丝断裂溶解、肌溶灶普遍存在等变化,并呈现出明显的剂量-效应关系;肝细胞表现弥漫性肿胀,细胞模糊,肝窦狭小,内皮细胞肿胀,结构模糊不清,细胞质内线粒体明显肿胀,糖原含量减少,与中毒剂量和时间均呈明显相关性。结论脑、心、肝可能为其毒性作用的主要靶器官或靶组织。     

对签字笔墨水的分析回顾及展望

文章叙述了目前国内外签字笔墨水的发展及主要成分,并介绍了分析签字笔墨水的方法。通过化学法和TLC法可以确定签字笔墨水是水性还是中性;利用GC／MS法可以确定签字笔墨水中溶荆成分及其变化;利用拉曼光谱法可以鉴别墨水中染料或颜料成分;利用红外反射法可将29种墨水分为三类;利用扫描电镜法可以通过颜料形态的差别鉴别颜料基墨水。