综合运用物证检验技术侦破命案2例

随着科技进步,现代法庭物证分析技术得到了飞速发展,在各类刑事案件的侦查中发挥着日益重要的作用.DNA检验技术及数据库的建设、环境扫描电镜能谱(ESEM/EDS)以及傅立叶变换红外显微光谱分析技术(Micro-FTIR)均是现代物证分析技术的重要组成部分,是刑侦破案的有力武器.本文对这3种物证分析技术在两起命案侦破中的综合应用作一介绍.     

毛发常见机械性损伤形态的环境扫描电镜研究

目的建立环境扫描电镜(ESEM)法推断毛发致伤物种类的新方法。方法应用ESEM观察分析不同锐器、钝器及致伤方式形成的毛发机械性损伤的微观形态特征。结果毛发锐器、钝器损伤的表面微观特征存在显著差异,同种类型致伤工具,其锋利程度、作用方式不同时,其损伤特征也明显不同。结论ESEM法能够真实、自然反映毛发机械性损伤表面微观特征,可应用于推断毛发致伤物种类。     

浅谈法庭科学实验室量值溯源的对策与途径

量值溯源是法庭科学实验室认可活动的重要内容之一，是法庭科学实验室检测结果可信性的基础，量值溯源的一致性是国际间相互承认测量结果的前提条件。根据ISO／IEC17025准则，申请认可和已经认可的法庭科学实验室所从事的检测活动，必须满足量值溯源的要求。法庭科学实验室在物证检验鉴定中，必须对用于检测的、对检测结果的准确性或有效性有显著影响的设备（包括环境监控设备）在投入使用前进行校准。本文就法庭科学实验室如何进行量值溯源作一阐述。     

泥土中花粉的环境扫描电镜研究

目的建立环境扫描电镜观察研究泥土中花粉的方法。方法泥土样品经过一系列酸碱浸泡、离心、过滤等处理后,经环境扫描电镜观察。环境扫描电镜采用样品室工作气压4.5torr,冷冻样品台温度5℃的工作条件。结果环境扫描电镜下观察到的花粉外壁雕纹饱满,层次感强,网状纹上的颗粒形态非常清晰,不同种花粉的外观形态特征各异。泥土样品提取后并可拍摄到清晰的花粉颗粒。结论采用环境扫描电镜可对泥土中花粉的形态进行观察,并可对已知花粉和未知花粉进行比较,进行种属鉴别。本方法可应用于实际案例,为鉴别花粉种类、确定泥土物证与犯罪现场的关系等提供科学依据。     

影像医学在法医学中的应用

个体识别在法庭科学调查中一直是重要的工作,它包括:性别、身高、年龄的推断等。在法庭科学领域中利用影像医学技术进行个体识别,在准确性、实用性方面有特别的意义。本文目的旨在通过广泛系统地回顾国内外法庭科学中的影像学应用,了解现有医学影像技术在法庭科学应用中的优点和不足之处,为进一步完善医学影像学在法庭科学中的应用提供参考。     

证据法的法域范围

法庭科学家和证据法学者所处的是两个不同的世界,就像英国和美国一样,由一种共通的语言划分开来。虽然在一些重要方面彼此关联,但法庭科学和证据法学作为两个独立的学科,有着各自独特的构造和演进,关注不同的问题并运用各具特色的认识论。因此,这两个学科之间存在着自说自话的重大风险。该风险的迹象体现在了法庭科学家与证据法学者之间时常沟通不畅。“证据法”的概念对于法庭科学和证据法学而言均至关重要,且在这两个学科中均被高频地运用。本文通过聚焦“证据法的法域范围”之基础概念讨论,希望造成该学科间冲突的个别成因能够明朗化,并诚挚地期盼这样做能有利于法庭科学与证据法学学科之间更有效地交流。     

美国法庭科学证据的应用与发展

＂法庭科学＂萌芽于古代中国,兴盛于近现代西方国家,最终发展成为具备完整科学体系的现代意义上的法庭科学学科。法庭科学证据的应用与发展显然与法庭科学的发展与应用密切相关,它们相互制约,相互促进。美国司法制度中关于法庭科学证据的证明力、可信度、可采性的分立质疑对法庭科学本身的发展无疑起到鞭策与促进作用。美国法庭科学证据的司法制度以及常用的一些传统与高技术法庭科学证据的使用过程中存在的许多问题,理解法庭科学证据标准,对我国法庭科学及其证据的研究与应用有所启迪。     

拉曼光谱技术在物证鉴定中的应用

拉曼光谱技术具有不接触样品、不破坏样品、无需样品制备等优点,适用于法庭科学领域不同种类物证的分析.本文综述了拉曼光谱技术在物证鉴定中的应用,并对该技术的发展趋势进行了展望.     

中外法庭科学标准化研究现状比较与发展趋势

近年来,我国法庭科学发展迅猛,开始受到广泛关注和重视。经过多年的研究和推动,标准化正逐步深入到法庭科学的日常实践中,通过制定和实施标准规范,确保法庭科学结果质量,更好发挥科学技术在执法司法中的重要作用。标准化研究是法庭科学标准化工作的重要环节,也是推动法庭科学标准化发展的基础和动力。国内外法庭科学研究者都高度重视法庭科学标准化研究,许多新理念、新思想、新方法不断涌现。本文从标准定位、标准化对象、标准颗粒度、标准体系、质量控制、国际标准化六个方面对当前中外法庭科学标准化研究的现状进行了深入全面的归纳和比较,指出了国内外在法庭科学标准化研究方面的相似和差异,并对法庭科学标准化研究的未来发展趋势进行了分析,以求为推动我国法庭科学领域标准化工作高质量发展提供借鉴和参考。     

我国法庭科学实验室认可工作现状与存在的问题

本文介绍了我国法庭科学实验室认可活动的法律环境变迁和开展现状,并对当前认可工作中存在的主要问题进行了深入分析,在此基础上提出7项政策建议。     

溺死的法医学检验现状及进展

本文概括阐述了近年来,国内外学者将硅藻的检验、内脏异物颗粒和微量元素成分的检验、血液化学的检验、电子显微镜的观察等方法应用于溺死的诊断,试图为溺死的法医学鉴定提供准确的诊断指标。     

A Novel Forensic Investigation Applied to Bone Remains Exhumed near to Quirra Interforce Firing Range

The need to implement novel techniques, able to support a causal link between exposure and pathology, has been emerged over the recent years. The application of scanning electron microscope coupled with probe X‐ray microanalysis (by means of an energy‐dispersive spectroscopy) has been developed by our research group for the bone remains investigation. It was aimed to testify the exposure to microsized and nanosized pollutions, due to military activities in the Quirra interforce firing range, of a Sardinian shepherd, died of acute leukemia. Metallic debris with a combustive morphology and with an oncogenic potential has been surely detected inside his bone marrow canal. This novel technique has proved to be able to bring to light a source of past exposure preserved over time within the bone marrow canal. It can be useful for postmortem analyses, delivering a new avant‐garde approach to modern forensic science.     

Examination of line crossings by atomic force microscopy

Until now, the most widely used methods for the forensic examination of line crossings in documents were optical and electron microscopy. The combination of both techniques allows one in most cases to establish the sequence of lines. The recent development of scanning probe microscopy [1] gives an opportunity to complement or even replace the classical instruments used in this field. Scanning probe microscopes have been designed to study surfaces at high magnification. The aim of this study was to verify if their most popular member, the atomic force microscope (AFM) [2], can be applied to line crossing problems. The results show for the first time that AFM images present the same qualitative information obtained by scanning electron microscope (SEM) images and, consequently, allow the determination of the line crossing sequence under ambient conditions without vacuum and conductive coating of specimens.     

Survey of gunshot residue analysis in forensic science laboratories

The purpose of this survey was to determine the methods of analysis being used on gunshot residue (GSR) samples in forensic science laboratories across the United States. In addition, the two general techniques of GSR analysis are compared and contrasted. Problems encountered by analysts using scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDX) are discussed.     

Assessment of Maceration Techniques Used to Remove Soft Tissue from Bone in Cut Mark Analysis

Maceration techniques employed in forensics must be effective without compromising the bone's integrity and morphology, and prevent destruction of evidence. Techniques must also be fast, safe, easily obtainable and inexpensive; not all techniques currently employed are appropriate for forensic use. To evaluate the most suitable approach, seven techniques including current and new methodologies were applied to fresh, fleshed porcine ribs exhibiting cut marks. A sample size of 30 specimens per technique was examined under scanning electron microscopy at the cut mark and the surrounding uncompromised regions; a scoring system of effectiveness was applied. The previously unpublished microwave method fared best for bone and cut mark preservation. Sodium hypochlorite destroyed cut marks, and was deemed unsuitable for forensic analysis. No single technique fulfilled all criteria; however, this study provides a benchmark for forensic anthropologists to select the most appropriate method for their situation, while maintaining the high standards required by forensic science.     

False-negative probability in the SEM/EDS automated discovery of iGSR particles: A Bayesian approach

The automated search software integrated with a scanning electron microscope (SEM/EDS) has been the standard tool for detecting inorganic gunshot residues (iGSR) for several decades. The detection of these particles depends on various factors such as collection, preservation, contamination with organic matter, and the method for sample analysis. This article focuses on the influence of equipment resolution setup on the backscattered electron images of the sample. The pixel size of these images plays a crucial role in determining the detectability of iGSR particles, especially those with sizes close to the pixel size. In this study, we calculated the probability of missing all characteristic iGSR particles in a sample using an SEM/EDS automated search and how it depends on the image pixel resolution setup. We developed and validated an iGSR particle detection model that links particle size with equipment registers and applied it to 320 samples analyzed by a forensic science laboratory. Our results show that the probability of missing all characteristic iGSR particles due to their size is below 5% for pixel sizes below 0.32 μm². These findings indicate that pixel sizes as large as twice the one commonly used in laboratory casework, that is, 0.16 μm², are effective for initial sample scanning, yielding good detection rates of characteristic particles that could exponentially reduce laboratory workload.     

Endothelial cell membrane perforation of aorta and pulmonary artery in the electrocution victims

Some electrocution deaths occur without detectable current marks on the skin, making forensic examination to determine the true cause of death more difficult. Because arterial thrombosis was a frequent finding in victims of electrocution, we investigated injury to the endothelium of the aorta and pulmonary artery with a scanning electron microscope in five cases of death known to be caused by electrocution. We found large pores on the surface of endothelial cells of the aorta and pulmonary artery in those who died of electrocution, but no endothelial membrane perforation was found in those who died of cardiac diseases. These findings were present within 12h after death. Therefore, scanning electron microscopic evidence of endothelial perforation in the aorta and pulmonary artery could be a useful marker to identify electrocution for those victims without detectable current marks on the skin.     

Limitations of ZAF correction factors in the determination of calcium/phosphorus ratios: important forensic science considerations relevant to the analysis of bone fragments using scanning electron microscopy and energy-dispersive x-ray microanalysis

A series of calcium phosphate standards having calcium/phosphorus (Ca/P) molar ratios of 0.50, 1.00, 1.50, and 1.67, respectively, was prepared for bulk specimen analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDXA). The standards were mounted on carbon planchettes as either pure crystals or crystals embedded in epoxy resin. Ten different samples of each embedded and non-embedded standard were analyzed in a JEOL 100 CX electron microscope interfaced with a Kevex 8000 EDXA system using a lithium-drifted silicon detector and a multichannel analyzer. The Ca/P ratios were determined by calculating both net peak intensities without matrix corrections and atomic kappa-ratios using the MAGIC V computer program with ZAF correction factors for quantitative analysis. There was such extensive absorption of phosphorus X-rays in standards embedded in an epoxy matrix that the observed Ca/P ratios were statistically compatible with four different standards ranging in theoretical Ca/P ratios from 1.0 to 1.67. Although the non-embedded crystals showed a greater separation in the Ca/P ratios, both methods of preparation produced serious flaws in analysis. Direct application of the discovery of this caveat to the identification of suspected bone fragments for forensic science purposes is discussed.     

Fourier transform infrared analyses of some particulate drug mixtures using a diamond anvil cell with a beam condenser and an infrared microscope.

Although the diamond anvil cell (DAC) has been used in many forensic science laboratories for the analysis of trace evidence, few applications of this technique for the analysis of controlled substances have been reported. This may be due to both an unfamiliarity on the part of forensic drug chemists with this accessory and the nature and quality of spectra that result from use of a DAC on a dispersive instrument. Along with low energy throughput, which results in relatively high noise levels, strong broad diamond absorptions occur. With the use of a Fourier transform infrared instrument, these do not present a problem and nanogram quantities of materials can be analyzed when the DAC is used with an infrared microscope. Since single crystals can be sampled with the DAC, simple physical separations (involving particle-picking) can be used in certain cases to isolate drugs from particulate mixtures for infrared analysis. This method is especially useful for some "difficult" mixtures and residues, and several examples of such analyses involving samples of forensic science interest are presented.     

Automated gunshot residue particle search and characterization

The main disadvantage to gunshot residue (GSR) particle analysis utilizing scanning electron microscope/energy dispersive X-ray (SEM/EDX) instrumentation has been the excessive operator time required for search and identification. This study uses an automated particle search and characterization program for unattended GSR search and identification. This system allows for automatic matrix search, particle sizing, chemical typing, and spectral aquisition with subsequent storage of data to disk for later operator review and verification. This work describes various aspects of the program, determines appropriate parameters adequate for both unique and characteristic GSR particle identification, and evaluates the reliability of data obtained. Samples are collected via the tape lift method from test-firings of .38, .32, .25, and .22 caliber handguns at time after firing intervals of 0 to 6 h. Unique GSR particles are consistently and correctly identified by this method on tape lift samples taken up to 4 h after firing. False positive results of unique GSR particles are not encountered on control handblank samples. This technique appears to provide the forensic science community with an operator-free method of reliable GSR particle search and an improved analyst-time-per-case ratio.