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.     

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。     

Identification and comparison of electrical tapes using instrumental and statistical techniques: I. Microscopic surface texture and elemental composition

Comparisons of polyvinyl chloride electrical tape typically rely upon evaluating class characteristics such as physical dimensions, surface texture, and chemical composition. Given the various techniques that are available for this purpose, a comprehensive study has been undertaken to establish an optimal analytical scheme for electrical tape comparisons. Of equal importance is the development of a quantitative means for sample discrimination. In this study, 67 rolls of black electrical tape representing 34 different nominal brands were analyzed via scanning electron microscopy and energy dispersive spectroscopy. Differences in surface roughness, calendering marks, and filler particle size were readily apparent, including between some rolls of the same nominal brand. The relative amounts of magnesium, aluminum, silicon, sulfur, lead, chlorine, antimony, calcium, titanium, and zinc varied greatly between brands and, in some cases, could be linked to the year of manufacture. For the first time, quantitative differentiation of electrical tapes was achieved through multivariate statistical techniques, with 36 classes identified within the sample population. A single-blind study was also completed where questioned tape samples were correctly associated with known exemplars. Finally, two case studies are presented where tape recovered from an improvised explosive device is compared with tape recovered from a suspect.     

Interpretation of automotive light bulb examination results: an intriguing case

During the examination of light bulbs from a vehicle involved in a road accident, the headlights did not reveal any evidence regarding whether they were energized or not. Additionally, a police officer turned the lights on after the accident to verify their functioning, thus damaging some of the evidence. By examining the vehicle, it was determined that the park lights could provide answers regarding the conditions of the headlights. After observations, it was concluded that the park lights and headlights were off at the time of the impact. This case report demonstrates how important it is to integrate the circumstances surrounding the case into the interpretation of the results. Nevertheless, it also demonstrates the necessity for examining both the vehicle and all light bulbs in order to reach the most pertinent and proper conclusion.     

Simultaneous detection and image capture of biological evidence using a combined 360° camera system with single wavelength laser illumination

Forensic investigators frequently utilise light sources to detect and presumptively identify biological evidence. The instrumentation typically deploys single or multiple wavelength exposures at various intensities, which interact with constituents of biological material, initiating fluorescence or improving contrast between the material and substrate. Documentation using sketches and/or photographic approaches follows detection, which are essential for scene reconstruction. Recent research has demonstrated the simultaneous detection and capture of biological evidence using a 360° camera system combined with an alternate light source exhibiting broad wavelength ranges of light. Single wavelength light sources reportedly offer enhanced sensitivity, due to the increased light intensity and narrower bandwidth of light, although their combined use with a 360° camera system has not yet been explored.Samples of human blood, semen, saliva, and latent fingermarks were deposited on to a variety of substrates. A 360° camera system combined with a laser light source was used to detect and capture the samples. Ten participants were asked to detect the samples on images of the substrates without ground truth knowledge. It was possible to detect and capture biological evidence, although success varied according to substrate colour and light intensity. Advantageously, presumptive screening for biological fluids and the simultaneous location and visualisation of such evidence as part of a 360° panorama of the scene for contextual purposes was permitted. There was no fluorescent response from the fingermarks, although the oblique lighting effects appeared sufficient to aid mark detection in some circumstances. The use of single wavelength illumination clearly facilitates identification of a range of forensically important material. When coupled with a 360-degree camera, this allows for simultaneous identification and recording of such evidence in the context of the whole environment.     

A Novel Application of a Cryosectioning Technique to Aid Scat Hair Microanalysis

Scat hair presents a diverse profile of hairs for morphological assessment that may find versatile applications in wildlife forensic investigations. Successful morphological assessment of scat hair microstructure, however, depends on a robust sectioning methodology. We assessed the feasibility and efficacy of a cryosectioning technique compared to that of a gold standard hand‐sectioning technique. Scat hairs were embedded in paraffin wax and hand‐sectioned, while cryopreserved scat hairs were sectioned with a cryostat. The results showed that cryosectioning preserved the pristine morphology of the scat hair and provided cross sections more amenable to high‐resolution imaging of hair internal microstructure than hand‐sectioning. The cryosectioning technique may find novel applications as a more reliable and robust technique to aid (i) scat hair internal microstructure analysis for cross‐referencing with species identification keys in wildlife forensic studies and (ii) downstream toxicological analysis in wildlife forensic studies as hair biochemistry is not altered during cryopreservation.     

Development and Validation of a Virtual Examination Tool for Firearm Forensics, ,

The transition from 2D imaging to 3D scanning in the discipline of firearms and toolmark analysis is likely to provide examiners an unprecedented view of microscopic surface topography. The digital examination of measured 3D surface topographies has been referred to as virtual microscopy (VM). The approach offers several potential advantages over traditional comparison microscopy. Like any new analytic method, VM must be validated prior to its use in a crime laboratory. This paper describes one of the first validation studies of virtual microscopy. Fifty‐six participants at fifteen laboratories used virtual microscopic tools to complete two proficiency‐style tests for cartridge case identification. All participating trained examiners correctly reported 100% of the identifications (known matches) while reporting no false positives. The VM tools also allowed examiners to annotate compared surfaces. These annotations provide insight into the types of marked utilized in comparative analysis. Overall, the results of the study demonstrate that trained examiners can successfully use virtual microscopy to conduct firearms toolmark examination and support the use of the technology in the crime laboratory.     

A Case of Contested Cremains Analyzed Through Metric and Chemical Comparison

Since the 1980s, cremation has become the fastest growing area of the U.S. funeral industry. At the same time, the number of litigations against funeral homes and cremation facilities has increased. Forensic anthropologists are often asked to determine whether the contents of an urn are actually cremated bone, and to address questions regarding the identity of the remains. This study uses both metric and chemical analyses for resolving a case of contested cremains. A cremains weight of 2021.8 g was predicted based on the decedent's reported stature and weight. However, the urn contents weighed 4173.5 g. The urn contents also contained material inconsistent with cremains (e.g., moist sediment, stones, ferrous metal). Analysis using XRD and SEM demonstrated that the urn contained thermally altered bone as well as inorganic material consistent with glass fiber cement. Although forensically challenging, cremains cases such as this one can be resolved using a multidisciplinary approach.     

Chemical Differentiation of Osseous and Nonosseous Materials Using Scanning Electron Microscopy–Energy-Dispersive X-Ray Spectrometry and Multivariate Statistical Analysis

Identification of osseous materials is generally established on gross anatomical features. However, highly fragmented or taphonomically altered materials may be problematic and may require chemical analysis. This research was designed to assess the use of scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM/EDX), elemental analysis, and multivariate statistical analysis (principal component analysis) for discrimination of osseous and nonosseous materials of similar chemical composition. Sixty samples consisting of osseous (human and nonhuman bone and dental) and non-osseous samples were assessed. After outliers were removed a high overall correct classification of 97.97% was achieved, with 99.86% correct classification for osseous materials. In addition, a blind study was conducted using 20 samples to assess the applicability for using this method to classify unknown materials. All of the blind study samples were correctly classified resulting in 100% correct classification, further demonstrating the efficiency of SEM/EDX and statistical analysis for differentiation of osseous and nonosseous materials.     

Timing and Appearance of Postmortem Root Banding in Nonhuman Mammals,

A study was undertaken using nonhuman mammal specimens to better understand environmental influences on postmortem hair root band (PMRB) formation and to see whether PMRBs would occur in nonhuman mammal hairs in a similar fashion to human hairs. Carcasses from surrounding roadways were the primary source of specimens for this study, augmented by donated deceased domestic pets. Sections of pelt from each specimen were placed in controlled environmental conditions while the remainder of the carcass was left in a secure outdoor setting. Hair samples were collected daily from outdoor and control specimens and examined for evidence of PMRBs. Several environmental factors were also recorded on a daily basis. Results demonstrate PMRBs can occur in nonhuman mammal hairs, and they have microscopic characteristics similar to human PMRBs. Factors found to correlate with PMRB formation include postmortem interval, temperature, pH, and the formation and subsequent volatilization of ammonia from the surrounding tissue.