Performance testing of commercial containers for collection and storage of fire debris evidence

Fire debris evidence may contain ignitable liquid residues valuable in the investigation of a potential arson scene. The ability to obtain evidence containers that are contaminant-free and vapor-tight is essential to the analysis and storage of fire debris evidence. Commercial containers such as metal "paint" cans, glass mason jars, and polymer bags are often employed as fire debris evidence containers. The purpose of this research was to determine which of these three types of containers provided the most vapor-tight seal for the prevention of ignitable liquid vapor loss and to assess the potential for cross-contamination. Leak rates for each type of container were measured under controlled conditions. Simple mixtures of hydrocarbons were utilized in these experiments. Leak rates were determined based on the amounts of hydrocarbon recovered from activated charcoal located outside the test container and within a secondary container. Quantitation of the hydrocarbons recovered from activated charcoal was calculated using external standard calibration curves following analysis by gas chromatography-mass spectrometry. The results demonstrated that glass jars had the fastest leak rate followed by metal paint cans and properly heat-sealed polymer bags with the slowest leak rate. Each container exhibited a different leak mechanism, which resulted in an observable effect on the composition of hydrocarbons lost from the container. Hydrocarbon transfer from one container to another is also demonstrated. This study presents results that reveal the most vapor-tight container to be a properly heat-sealed copolymer bag.     

The use of a tunable light source (Mini-Crimescope MCS-400, SPEX Forensics) in dissecting microscopic detection of cryptic epithelial particles

As skin particles are often deposited by even a single skin contact, the detection of skin debris is important for evidence collection and DNA testing. Unfortunately, even when a dissecting microscope is used by an experienced examiner, epidermal particles are often hard to find and these traces of evidence might escape DNA analysis. Fluorescence is defined as the property of absorbing short-wavelength light and emitting longer-wavelength light. By virtue of the fluorescence characteristics of many target materials, tunable light sources assist in the macroscopic search of crime scenes and items. We combined the dissecting microscope and an alternate light source to examine the fluorescence characteristics of skin and skin particles. In a comparative study, small skin scales were hidden between sand, fibers, and soil probes, and it proved possible to search more successfully with less time and effort. On staged casework exhibits, the efficiency of the screening aid was again tested and the usability of the new procedure shown.     

An initial evaluation of stable isotopic characterisation of post-blast plastic debris from improvised explosive devices

A number of two-way radios, similar to those which have been employed to initiate Improvised Explosive Devices (IEDs), were acquired from a commercial supplier and grouped into four pairs. Samples of plastic material were collected from five distinct regions of each radio and analysed by Infrared and Raman spectroscopy to identify the nature of the material. One radio of each pair was then subjected to detonation with a commercially available plastic explosive. The combination of radio and explosive was considered to be representative of the components of an IED. Following detonation, fragments were recovered and, where possible, identified as specific sampling points of the radio.A combination of δ²H and δ¹³C stable isotopic analysis of material from each of the five sampling points was found to provide a pattern which was characteristic of a given radio and provided a means to associate pairs of radios. When few fragments were recovered, no positive association could be made between the fragments and the paired, undamaged radio. This was attributed, in part, to manufacturing variation in the radios. However, when three or more post-blast fragments were recovered it was possible to associate these with the paired, undamaged radio with a high degree of certainty.     

防火墙技术分析

Internet的迅速发展给现代人的生产和生活都带来了前所未有的飞跃,大大提高了工作效率,丰富了人们的生活,弥补了人们的精神空缺;而与此同时给人们带来了一个日益严峻的问题——网络安全。网络的安全性成为当今最热门的话题之一,很多企业为了保障自身服务器或数据安全都采用了防火墙。随着科技的发展,防火墙也逐渐被大众所接受。本文阐述了防火墙工作的方式,以及防火墙的基本分类,并且讨论了每一种防火墙的优缺点。     

公安消防队灭火行为的法律属性及对诉讼风险的规避

近年来,消防灭火涉诉案件有逐年增多的趋势,从而引发了对公安消防队灭火行为的性质的争议。公安消防队的灭火行为应属于行政行为。公安消防机构不应回避被诉的事实,而应有规避诉讼风险的意识和策略。     

对闲置出租厂房火灾隐患的研析及防治对策

随着我国社会主义市场经济体制改革的不断深入,一些曾经是国有大中型企业集中的区域,经过十几年来的改革、重组、改制或迁址,遗留下了大量的闲置厂房。由于缺乏规范的管理机制,加之闲置厂房大多条件较差,在外来务工人员居住、生产过程中,暴露出许多火灾隐患、明患。为此,必须建立对闲置出租厂房的管理、监督、检查和整改的长效机制,以避免发生群死群伤的治安灾害事故。     

A review of the analysis of vegetable oil residues from fire debris samples: analytical scheme, interpretation of the results, and future needs

This paper reviews the literature on the analysis of vegetable (and animal) oil residues from fire debris samples. The examination sequence starts with the solvent extraction of the residues from the substrate. The extract is then prepared for instrumental analysis by derivatizing fatty acids (FAs) into fatty acid methyl esters. The analysis is then carried out by gas chromatography or gas chromatography-mass spectrometry. The interpretation of the results is a difficult operation seriously limited by a lack of research on the subject. The present data analysis scheme utilizes FA ratios to determine the presence of vegetable oils and their propensity to self-heat and possibly, to spontaneously ignite. Preliminary work has demonstrated that it is possible to detect chemical compounds specific to an oil that underwent spontaneous ignition. Guidelines to conduct future research in the analysis of vegetable oil residues from fire debris samples are also presented.     

做好消防行政案件法律审核工作的思考

随着新修订的《中华人民共和国消防法》的颁布,对促进公正、严格、文明、高效执法提出了更新、更高的要求。法律审核制度正是加强和规范内部执法监督工作,保障各项监督执法活动合法、规范的必要手段。笔者结合昆明市消防监督执法办案工作的实际及日常法律审核工作,就如何做好行政处罚案件的法律审核工作提出几点思考。     

浅议公安派出所的消防监督检查职能

《消防法》第五十三条规定了公安派出所的消防监督检查职能。因存在思想认识不足、制度激励不足、资源配置不足、知识供给不足等原因,公安派出所履行消防监督检查职能的现状不容乐观。因此,必须采取有力措施,促使公安派出所切实履行法律所赋予的消防监督检查职能。     

Progress Toward the Determination of Correct Classification Rates in Fire Debris Analysis,,

Principal components analysis (PCA), linear discriminant analysis (LDA), and quadratic discriminant analysis (QDA) were used to develop a multistep classification procedure for determining the presence of ignitable liquid residue in fire debris and assigning any ignitable liquid residue present into the classes defined under the American Society for Testing and Materials (ASTM) E 1618‐10 standard method. A multistep classification procedure was tested by cross‐validation based on model data sets comprised of the time‐averaged mass spectra (also referred to as total ion spectra) of commercial ignitable liquids and pyrolysis products from common building materials and household furnishings (referred to simply as substrates). Fire debris samples from laboratory‐scale and field test burns were also used to test the model. The optimal model's true‐positive rate was 81.3% for cross‐validation samples and 70.9% for fire debris samples. The false‐positive rate was 9.9% for cross‐validation samples and 8.9% for fire debris samples.