爆炸案件现场重建初探

随着国际恐怖主义活动的日益猖獗,爆炸案件也呈逐年上升之势,爆炸案件向来是公安机关重点打击的刑事犯罪之一,因此爆炸案件的侦破工作显得尤为重要。而现场重建运用于现场破坏严重、现场范围大且难度天的爆炸案件现场勘查中有其独特的优势。分析爆炸案件特点、爆炸现场重建要解决的问题,探讨采集现场重建各要素的方式,整合刑事技术方面的多重信息,针对爆炸现场最大限度地提出重建与恢复的步骤、方法,从而使现场重建在爆炸案件侦破工作中发挥其重要作用。     

论爆炸现场的救援和身份认证——以恐怖主义爆炸袭击为背景

恐怖主义是威胁当今世界和平的一个重要因素,目前恐怖活动在全球有愈演愈烈的趋势;我国在新世纪也同样面临恐怖袭击的威胁。爆炸手段是恐怖分子发动袭击的主要手段,爆炸现场的救援和身份认证是各国应对恐怖袭击的难题。本文介绍了恐怖主义爆炸案件的概念,分析了恐怖主义爆炸袭击常用的手段和现场的特点,借鉴以色列的经验,论述了现场救援和身份认证的程序和步骤。     

Evaluation of canine training aids containment for homemade explosive and components by headspace analysis and canine testing

While canines are most commonly trained to detect traditional explosives, such as nitroaromatics and smokeless powders, homemade explosives (HMEs), such as fuel–oxidizer mixtures, are arguably a greater threat. As such, it is imperative that canines are sufficiently trained in the detection of such HMEs. The training aid delivery device (TADD) is a primary containment device that has been used to house HMEs and HME components for canine detection training purposes. This research assesses the odor release from HME components, ammonium nitrate (AN), urea nitrate (UN), and potassium chlorate (PC), housed in TADDs. Canine odor recognition tests (ORTs) were used with analytical data to determine the detectability of TADDs containing AN, UN, or PC. Headspace analysis by gas chromatography/mass spectrometry (GC/MS) with solid-phase microextraction (SPME) or online cryotrapping were used to measure ammonia or chlorine, as well as other unwanted odorants, emanating from bulk AN, UN, and PC in TADDs over 28 weeks. The analytical data showed variation in the amount of ammonia and chlorine over time, with ammonia from AN and UN decreasing slowly over time and the abundance of chlorine from PC TADDs dependent on the frequency of exposure to ambient air. Even with these variations in odor abundance, canines previously trained to detect bulk explosive HME components were able to detect all three targets in glass and plastic TADDs for at least 18 months after loading. Detection proficiency ranged from 64% to 100% and was not found to be dependent on either age of material.     

公安机关现场勘验信息系统存在的问题及对策

全国公安机关现场勘验信息系统是公安机关三基工程的重点建设项目之一,对增强勘查能力、优化侦查模式、提升破案效益、提高科学打击犯罪水平等具有重要作用。但是,在日常使用过程中,系统的功能未得到充分发挥。     

A Comparison of Four Presumptive Tests for the Detection of Blood on Dark Materials

Detection of blood on dark materials is difficult for crime scene examiners so presumptive tests are used to assist. This study compared the ability of luminol, leuko crystal violet, tetramethylbenzidine, and Combur Test®E to detect whole, diluted blood (1:100) and a key‐shaped blood transfer stain (1:10), on dark cotton sheeting, tea towel, socks, synthetic carpet, and car mats. Powdered bleach was used to evaluate specificity of the blood detection tests. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall misclassification rate (OMR) assessed the quality of the blood tests. Luminol was the preferred test for diluted blood having the highest sensitivity (79%–96%), NPV (66%–93%), and the lowest OMR (3%–15%). Luminol was also found to be most efficient with a testing time on 25 items of 2 h 50 min compared with up to 8 h. Overall, luminol was the most effective method, also providing information on bloodstain patterns.     

Explosion Scene Forensic Image Interpretation

Image interpretation is an important aspect in the field of forensic science; however, it is seldom reported how to use these techniques in explosion scene forensic investigations. On 12 August 2015, a series of explosions killed 165 people and injured hundreds more at a container storage station at the Port of Tianjin. In this study, we applied image interpretation methods to determine the seat of the explosion by analyzing low‐quality video clips of the event. The interpretation fits well with recently published standard operating procedures, including the hypothesis, evaluation, inference, and confirmation. Image processing was adopted to enhance the images while the explosion scene was reconstructed with the same images. Some important features were extracted and utilized to distinguish whether the flashes were caused by reflection or a real blast. We reveal the real explosion location, which guides the overall investigation. The results indicate that image interpretation is a powerful tool for forensic investigators to analyze low‐quality images in complicated explosions or fire accidents.     

The importance of dark adaptation for forensic examinations; an evaluation of the Crime-lite Eye™

Forensic practitioners are recommended to dark adapt their eyes prior to conducting evidential searches in the dark. The dark adaptation process remains poorly standardised across the discipline, with little quantified regarding the benefits of such preparative steps. Herein, we report the findings of a study that recruited 50 participants to assess the effectiveness of the Crime-lite Eye?, a darkness adaptation device developed to assist forensic practitioners both in the laboratory and in field. Participants were tasked with searching for the fluorescent signatures left by reaction of 1,8-diazafluoren-9-one (DFO) with amino acids, in a manner akin to the fluorogenic fingerprint treatment of porous evidence. Using an Epson Stylus Photo R265 inkjet printer, ink cartridges were filled with alanine solutions of various concentrations, allowing different motifs to be printed onto copy paper and subsequently developed using DFO. Participants searched for this ‘evidence’ both with and without dark adapted vision. On average, participants were able to locate and correctly recognise 16% more evidence once dark adapted using the Crime-lite Eye?.The increase in evidence located by participants once dark adapted suggests that crime scene officers should be dark adapting in order to visualise as much as possible. The time taken to dark adapt, 10?min on average during this study, is not excessively long, and should not significantly slow the investigation.     

Can analysis of a small clod of soil help to solve a murder case?

Soil forensics utilizes extensive soil information to answer legal questions and test hypotheses. The main difficulty often is the determination of different variables from a small amount of soil sample collected on the suspect. We developed a sequential mineralogical and chemical analyses to assess a limited quantity of soil vestiges (0.5 g) from a suspect's vehicle (adhered to the outside rear-view mirror and to the left front fender) involved in a murder case and compared them with the surface samples found at the victim's body disposal site at the Graciosa Road, Paraná State, Brazil. All results affirm that the suspect’s vehicle could have been in contact with the edge of the Graciosa Road, approximately the place where the victim’s body was located. As a result of the soil analysis and comparison, the results support the likely contact of the suspect’s vehicle with the crime scene.     

Hierarchical,Three‐Dimensional Measurement System for Crime Scene Scanning

We present a new generation of three‐dimensional (3D) measuring systems, developed for the process of crime scene documentation. This measuring system facilitates the preparation of more insightful, complete, and objective documentation for crime scenes. Our system reflects the actual requirements for hierarchical documentation, and it consists of three independent 3D scanners: a laser scanner for overall measurements, a situational structured light scanner for more minute measurements, and a detailed structured light scanner for the most detailed parts of tscene. Each scanner has its own spatial resolution, of 2.0, 0.3, and 0.05 mm, respectively. The results of interviews we have conducted with technicians indicate that our developed 3D measuring system has significant potential to become a useful tool for forensic technicians. To ensure the maximum compatibility of our measuring system with the standards that regulate the documentation process, we have also performed a metrological validation and designated the maximum permissible length measurement error E_MPE for each structured light scanner. In this study, we present additional results regarding documentation processes conducted during crime scene inspections and a training session.     

The Relationship Between Deprivation and Forensic Material Recovered from Stolen Vehicles: Is it Affected by Vehicle Condition and Tidiness?

Previous research has shown that as crime scene location deprivation increases (lower socioeconomic status), the recovery of forensic material, principally DNA and fingerprints, also increases. However, this increase does not result in more crimes being solved by forensic means. In this study, we analyze stolen vehicle data and find a statistically significant positive association between deprivation and the amount of forensic material that matched either the victim or an associate of the victim on a criminal database. The nature of this association was investigated further by inspecting recovered stolen vehicles to establish whether the condition of a stolen vehicle and the tidiness of its interior influenced the recovery of forensic material that was attributed to the victim or an associate. Contradictory results suggest that other factors may contribute to understanding the association between the recovery of victim- or associate-attributable forensic material and crime scene location deprivation.