环境扫描电镜在法庭科学中的应用

介绍了环境扫描电镜中二次电子成像的原理及在非导电样品、含水含油样品、植物及生物样品中的应用.     

Forensic Investigation of a Shawl Linked to the “Jack the Ripper” Murders

A set of historic murders, known as the “Jack the Ripper murders,” started in London in August 1888. The killer's identity has remained a mystery to date. Here, we describe the investigation of, to our knowledge, the only remaining physical evidence linked to these murders, recovered from one of the victims at the scene of the crime. We applied novel, minimally destructive techniques for sample recovery from forensically relevant stains on the evidence and separated single cells linked to the suspect, followed by phenotypic analysis. The mtDNA profiles of both the victim and the suspect matched the corresponding reference samples, fortifying the link of the evidence to the crime scene. Genomic DNA from single cells recovered from the evidence was amplified, and the phenotypic information acquired matched the only witness statement regarded as reliable. To our knowledge, this is the most advanced study to date regarding this case.     

Resolving Reflection and Resolution in 3D Imaging of Fresh Bone

Structured light scanning is a noninvasive, accurate, and cost-effective 3D imaging technique, but due to reflection issues is yet to be utilized for tool mark analysis on fresh bone. During imaging, reflection from shiny surfaces, such as greasy bone, disrupts image formation. This study tested the David SLS-1 scanner's ability to image saw marks and explored six strategies to reduce reflection by [1] dulling the surface or [2] altering the projected light. The surface was dulled by freezing, talcum powder, dulling spray, or compressed air. The projected light was altered with a diffuser or limited to single pattern-coded. Results demonstrated that the resolution was insufficient for capturing minute details of striae. All six tests failed to reduce reflection sufficiently to produce complete images, but projecting vertical pattern-coded light showed the most promise. Future research is required concentrating on enhancing resolution and exploring the role of pattern-coded light in reducing reflection.     

Toner Particles as Forensic Evidence: Microanalytical Characterization of Known Toner and Recognition of Toner in Environmental Samples*†‡

Modern printing toners represent a prime example of subvisible particles that can be easily transferred to hands, clothing, and other surfaces. To explore the potential evidentiary value of toner particles, toner samples were collected from known printer cartridges and characterized by various microanalytical techniques to establish the properties most useful for recognition, identification, and comparison. Environmental samples (i.e., dust) were then collected from various locations at varying distances from toner-based printers, using both tape lifts and carbon adhesive stubs, to assess the possibility of detecting toner. By light microscopy, toner can be recognized on the basis of particle size and shape, as well as color. Further examination of the micromorphology in the field emission scanning electron microscope reveals characteristic morphologies and differences in surface texture and shape among toner sources. Raman spectroscopy provides chemical identification of the pigment (or pigment class) and, in some cases, also permits identification of the polymer component. While black and blue pigment chemistry remained constant among toner varieties that were studied (copper phthalocyanine and carbon black), variation in yellow and magenta pigments was observed. Analysis of dust samples collected from various environments demonstrated that while toner is consistently detectable in close proximity to printers (within 2 feet), it also can be detected in dust collected in nearby rooms. This research demonstrates that toner particles can be located, characterized, and discriminated, using a suite of microanalytical methods that are applicable to forensic casework.     

Computer controlled scanner for laser enhanced photography

The use of a scanner to control the photography of fingerprints, shoeprints and other trace contacts which fluoresce under irradiation from an argon ion laser is described. This scanner has been built to cover areas varying in size from a single fingerprint to a shoeprint and provides for variable speed, step size and angle of radiation which are all very important in this highly specialised area of photography.     

尸僵再形成的实验性研究

目的观察尸僵再形成中肌节长度的变化。方法应用扫描电镜测定不同条件下取材的40只大鼠股四头肌肌节长度,判断再僵直的强度。结果死后未破坏的尸僵肌节的长度明显小于尸僵再形成时的长度。结论肌节长度与尸僵强度呈负相关,说明肌节长度可确定尸僵强度,从而为推断死亡时间提供依据。     

地面三维激光扫描在交通事故勘查及重建中的应用进展

本文回顾了地面三维激光扫描技术的发展历程和应用场景,简要阐述了地面三维激光扫描系统的技术原理和作业流程,对地面三维激光扫描技术在交通事故领域的应用进行分类,并详细梳理了各类别下的最新研究成果与实例,结合交通事故勘查和重建发展需求,探讨了目前存在的问题和未来发展方向。     

MALDI-TOF-MS对DAI大鼠脑干蛋白质组学的分析

目的应用基质辅助激光解吸/电离-飞行时间质谱(matrix-assisted laser desorption/ionization timeof-flight mass spectrometry,MALDI-TOF-MS)技术建立弥漫性轴索损伤(diffuse axonal injury,DAI)诊断模型,筛选DAI相关蛋白或多肽,为寻找DAI的分子标志物提供理论基础。方法将15只雄性SD大鼠随机分为DAI组(n=10)和对照组(n=5),采用MALDI-TOF-MS技术对两组大鼠脑干组织的蛋白或多肽表达谱进行检测,运用Clin Pro Tools 2.2分析软件筛选出具有差异的分子峰,应用遗传算法建立诊断模型。结果筛选出有差异的分子峰61个(P0.05),其中DAI组有9个分子峰下调,52个分子峰上调。筛选出5个分子峰建立诊断模型,交叉验证的特异性为96.14%、敏感性为95.98%,盲法验证结果的特异性为73.33%、敏感性为70.00%。结论应用MALDI-TOF-MS技术不仅能够建立特异性和敏感性较高的DAI诊断模型,还可以筛选差异蛋白或多肽,为DAI的法医学鉴定奠定理论基础。     

Preparation of a Ytterbium‐tagged Gunshot Residue Standard for Quality Control in the Forensic Analysis of GSR

Preparation of a ytterbium‐tagged gunshot residue (GSR) reference standard for scanning electron microscopy and energy dispersive X‐ray spectroscopic (SEM‐EDS) microanalysis is reported. Two different chemical markers, ytterbium and neodymium, were evaluated by spiking the primers of 38 Special ammunition cartridges (no propellant, no projectile) and discharging them onto 12.7 mm diameter aluminum SEM pin stubs. Following SEM‐EDS microanalysis, the majority of tri‐component particles containing lead, barium, and antimony (PbBaSb) were successfully tagged with the chemical marker. Results demonstrate a primer spiked with 0.75% weight percent of ytterbium nitrate affords PbBaSb particles characteristic of GSR with a ytterbium inclusion efficiency of between 77% and 100%. Reproducibility of the method was verified, and durability of the ytterbium‐tagged tri‐component particles under repeated SEM‐EDS analysis was also tested. The ytterbium‐tagged PbBaSb particles impart synthetic traceability to a GSR reference standard and are suitable for analysis alongside case work samples, as a positive control for quality assurance purposes.     

An Investigation into the Effects of Force Applied During Deposition on Latent Fingermarks and Inked Fingerprints Using a Variable Force Fingerprint Sampler

Physical factors, including the magnitude of the force applied during fingermark deposition, may affect friction ridge surface area and clarity, and the quantity of residue transferred. Consistency between fingermarks may be required; for example, in research projects, yet differences between marks are likely to exist when physical factors are not controlled. Inked fingerprints and latent fingermarks were deposited at 1–10 N at 1 N increments using a variable force fingerprint sampler to control the force, angle of friction ridge and surface contact, and the duration of friction ridge and surface contact. Statistically significant differences existed between the length and width measurements of the inked prints (p ≤ 0.05), particularly at lower forces. Scanning electron microscopy and surface plot analysis demonstrated how differences in force applied during deposition affected ridge surface area, displacement of latent residue, and differences in the quantity of residue transferred. Consistency between inked prints was demonstrated at equivalent forces.