Carbon‐Based Fingerprint Powder as a One‐Step Development and Matrix Application for High‐Resolution Mass Spectrometry Imaging of Latent Fingerprints

Carbon‐based materials are often used as matrices for matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) and its imaging (MALDI‐MSI). However, researchers have refrained from using carbon‐based fingerprint powder (CFP) as a matrix due to high background and contamination. In this work, the compatibility of CFP is reevaluated with MALDI‐MSI using a high‐resolution mass spectrometer (HRMS) and compared to traditional organic matrices. Relevant fingerprint compounds were easily distinguished from carbon cluster peaks when using HRMS. For fair comparison, half of a fingerprint was dusted with CFP while the other half was dusted with traditional organic matrices. All compounds studied had comparable, or higher, signal‐to‐noise (S/N) ratios when CFP was used as the matrix. Additionally, chemical image qualities closely followed the trend of S/N ratios. CFP proved to be an effective one‐step development and matrix application technique for MALDI‐MSI of latent fingerprints, when carbon cluster peaks are well separated by a HRMS.     

Application of MALDI‐TOF MS for Estimating the Postmortem Interval in Rat Muscle Samples

Estimating the postmortem interval (PMI) is very important in the forensic sciences. Although many approaches have been used for estimating the PMI, accurate PMI calculations are still difficult. In this study, four Sprague Dawley (SD) rats were sacrificed by suffocation, and muscle samples were collected by dissection at various time intervals (0, 48, 96, and 144 h) after death. All samples were probed using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) to obtain molecular images and data for principal component analysis (PCA). The results showed that the peaks at m/z 1511, 1543, 1564, 1586 clearly decreased in intensity from 0 to 144 h postmortem and that the time groups were separated from each other on the PCA score plot. The prediction model showed high recognition capability (95.93%) and cross‐validation (83.72%). Our work suggests that MALDI‐TOF MS can be used to determine the PMI.     

Effect of History and Context on Forensic Pathologist Interpretation of Photographs of Patterned Injury of the Skin

In a previous study, a survey‐based analysis of pathologist diagnoses of patterned injury was performed. Subjects were provided with photographs of “classic” injuries and asked to diagnose the lesion in the absence of history or context. There was a relatively low diagnostic consensus among respondents. A second survey suggested that the disparate answers were not due to a strong belief in different diagnoses, but instead reflected how the respondents dealt with ambiguity. A third survey was created that asked participants to evaluate patterned injuries of the skin, but provided history and contextual information. The addition of history and contextual information increased consensus from a median of 80% to 98% on a per‐question basis. Confidence increased from a median of 56%–92%. These results demonstrate the importance of history and context in medical diagnosis of patterned injuries of the skin.     

4种影像学检查方法应用于肩关节损伤法医学鉴定的比较

目的 评价X线、CT、MRI及CT气-碘双对比造影4种方法在肩关节损伤法医学鉴定中的应用价值.方法通过对肩关节损伤患者行X线摄片、CT扫描、MRI成像与CT气-碘双对比造影检查,观察、分析4种方法所得的影像学资料.结果 X线摄片对骨折的诊断率为52.8%,对软组织损伤的诊断率为0%;CT对骨折的诊断率为72.0%.对软...     

差示扫描量热法检验合成纤维

目的研究不同种类合成纤维以及不同厂家生产的同种类合成纤维的鉴别方法。方法应用功率补偿型差示扫描量热仪测定涤纶、腈纶、锦纶、丙纶、氨纶、氯纶等6种常见合成纤维和10个厂家生产的涤纶纤维的DSC曲线,并对热学参数进行计算和分析。结果涤纶、腈纶、锦纶、丙纶、氨纶、氯纶的DSC曲线明显不同,10个厂家生产的涤纶纤维的DSC曲线虽然非常相近,但对其熔融温度Tm、熔融峰顶温度Tmp、熔融焓变ΔHm、结晶温度Tc、结晶峰顶温度Tcp和结晶焓变ΔHc等热学参数的计算结果显示,10个涤纶纤维的参数并不完全相同。结论差示扫描量热法不但能对不同种类的合成纤维进行鉴别,也可区分不同厂家生产的同种类纤维,从而为案件侦破提供更为准确的方向、线索和证据。     

基于水印技术的司法数码影像防伪信息系统

数码影像作为证据使用存在一定的争议,针对此提出并建立了基于水印技术的司法数码影像防伪信息系统,该系统由加密防伪子系统、信息管理子系统和加密信息验证子系统组成,为确保司法数码影像的证据效力提供了一种技术方案。     

High Resolution Imaging of Latent Fingerprints by Localized Corrosion on Brass Surfaces

Abstract:  The Atomic Force Microscope (AFM) is capable of imaging fingerprint ridges on polished brass substrates at an unprecedented level of detail. While exposure to elevated humidity at ambient or slightly raised temperatures does not change the image appreciably, subsequent brief heating in a flame results in complete loss of the sweat deposit and the appearance of pits and trenches. Localized elemental analysis (using EDAX, coupled with SEM imaging) shows the presence of the constituents of salt in the initial deposits. Together with water and atmospheric oxygen—and with thermal enhancement—these are capable of driving a surface corrosion process. This process is sufficiently localized that it has the potential to generate a durable negative topographical image of the fingerprint. AFM examination of surface regions between ridges revealed small deposits (probably microscopic "spatter" of sweat components or transferred particulates) that may ultimately limit the level of ridge detail analysis.     

A Statistical Validation of the Individuality and Repeatability of Striated Tool Marks: Screwdrivers and Tongue and Groove Pliers*

Abstract: Tool mark identification relies on the premise that microscopic imperfections on a tool’s working surface are sufficiently unique and faithfully transferred to enable a one‐to‐one association between a tool and the tool marks it creates. This paper presents a study undertaken to assess the validity of this premise. As part of this study sets of striated tool marks were created under different conditions and on different media. The topography of these tool marks was acquired and the degree of similarity between them was quantified using well‐defined metrics. An analysis of the resulting matching and nonmatching similarity distributions shows nearly error‐free identification under most conditions. These results provide substantial support for the validity of the premise of tool mark identification. Because the approach taken in this study relies on a quantifiable similarity metric, the results have greater repeatability and objectivity than those obtained using less precise measures of similarity.     

Effect of Aging and Surface Interactions on the Diffusion of Endogenous Compounds in Latent Fingerprints Studied by Mass Spectrometry Imaging,

The ability to determine the age of fingerprints would be immeasurably beneficial in criminal investigations. We explore the possibility of determining the age of fingerprints by analyzing various compounds as they diffuse from the ridges to the valleys of fingerprints using matrix‐assisted laser desorption/ionization mass spectrometry imaging. The diffusion of two classes of endogenous fingerprint compounds, fatty acids and triacylglycerols (TGs), was studied in fresh and aged fingerprints on four surfaces. We expected higher molecular weight TGs would diffuse slower than fatty acids and allow us to determine the age of older fingerprints. However, we found interactions between endogenous compounds and the surface have a much stronger impact on diffusion than molecular weight. For example, diffusion of TGs is faster on hydrophilic plain glass or partially hydrophilic stainless steel surfaces, than on a hydrophobic Rain‐x treated surface. This result further complicates utilizing a diffusion model to age fingerprints.     

Study of the adhesion of explosive residues to the finger and transfer to clothing and luggage

It is important to understand the extent of transfer of explosive particles to different surfaces in order to better evaluate potential cross-contamination by explosives in crowded security controls such as those at airports. This work investigated the transfer of nine explosive residues (ANFO, dynamite, black powder, TNT, HMTD, PETN, NH₄NO₃, KNO₃, NaClO₃) through fingerprints from one surface to another. First, the extent of adhesion of explosive residues from different surfaces to the bare finger, nitrile and latex gloves was studied. Then, the transfer of explosive residues from one surface to another through fingerprints was investigated. Cotton fabric (hereinafter referred to as cotton) as clothing material and polycarbonate plastic (hereinafter referred to as polycarbonate) as luggage material were chosen for the experiments. These surfaces containing explosive particles were imaged using a reflex camera before and after the particles were transferred. Afterwards the images were processed in MATLAB where pixels corresponding to explosive residues were quantified. Results demonstrated that transfer of explosive residues frequently occurred with certain differences among materials. Generally, the amount of explosive particles adhered to the finger decreased in the following order: skin>latex>nitrile, while the transfer of particles from the finger to another surface was the opposite. The adhesion of explosive residues from polycarbonate to the finger was found to be better compared to cotton, while the amount of particles transferred to cotton was higher.