The Accuracy and Repeatability of Reconstructing Single Bullet Impacts Using the 2D Ellipse Method

When a bullet punctures a surface, it leaves behind a bullet impact, which can be analyzed in order to determine the origin and trajectory path from which a bullet was discharged using many different scientific methods to reconstruct a shooting scene. The purpose of the research was to test the accuracy and repeatability of reconstructing the impact angle of single bullet impacts using the ellipse method. The research was conducted by firing various calibers of ammunition into drywall panels positioned at varying angles of incidence from 88° until ricochet occurred. This was done in order to determine which caliber type and angle of incidence are most accurate and precise for reconstructing a shooting scene. The study examined four caliber types fired into drywall panels, with 5 repeated shots for each of the 11 angles of incidence (n = 220). Furthermore, 31 participants partook in the study to estimate a bullet impact angle of incidence utilizing the ellipse method. The results show that the best performance (accuracy and repeatability) is seen with the measurements of the 0.45 caliber ammunition. When angle of incidences is low (<64°), the performance (accuracy and repeatability) was seen to be better in all caliber ammunitions. Overall, the data provided for single bullet impacts deposited in drywall show that the ellipse method is useful in providing measurements for most crime scene reconstruction purposes and has also demonstrated that results vary depending on the type of ammunition, firearm, and angle of incidence being examined.     

Two-dimensional metric comparisons between dynamic bare footprints and insole foot impressions-forensic implications

Footwear may be found at crime scenes as physical evidence. Such footwear often has impression features of the wearer’s foot on the insole of the shoe. Scientific research and literature have established that footprints are distinct. This study compares two-dimensional measurements on bare footprints to foot impressions on insoles to determine if significant differences or similarities exist. Dynamic footprints were collected from 51 donors using the Identicator® Inkless Shoe Print Model LE 25P system. Seven foot length and width measurements were taken based on the Reel linear measurement method. Footprint measurements between bare footprints and foot impressions on the insoles were compared. Only two differences (p > 0.05) were observed between the various bare footprint and insole foot impression measurements on the right and left side for most of the measurements, CALC (p < 0.001) and A1 (p = 0.04). Bare footprint and insole A5 measurements on the left side were also significantly different (p = 0.015). The results of the study have implications in the forensic analysis of foot impression evidence on insoles in footwear in assisting with identifying the wearer of said footwear. Situations may arise in the forensic context when comparing the foot impression on the insole of footwear to a suspect’s bare footprint or a footprint from post-mortem remains. This study contributes to the scant literature available on the topic and to understanding the similarities and differences observed in the various linear measurements that may be utilized in the comparison process of footprint impressions on shoe insoles to bare footprints.     

犯罪现场反常情况的成因

犯罪现场反常情况是侦查初期开展侦查工作的一大障碍;但只要找准其成因,并运用正确的方法加以识别和排除,据此展开侦查反而会成为侦破案件的一条捷径。犯罪现场反常情况的形成原因一般包括犯罪人的伪装、偶然因素的介入、环境因素、犯罪人的特殊犯罪目的、犯罪分子的附带作案心理等方面。     

楼房入室盗窃案件的特点和现场勘查技巧

楼房入室盗窃案件呈逐年上升之势,已成为城市严重治安问题之一。楼房入室盗窃案件的侵害目标具体,时机选择比较固定,作案手段具有特殊性和习惯性,多为团伙流窜作案,现场容易被破坏。深入分析楼房入室盗窃案件的特点,掌握此类案件的现场勘查技巧,提高现场勘查质量,是快速破获此类案件的先决条件。     

Civilian Forensic Technician and Sworn Police Officer Job-Related Stress

Forensic Technicians provide crime scene investigation services and are exposed to stressful violent crimes, motor vehicle accidents, biological or chemical hazards, and other appalling imagery. Forensic Technicians would likely experience physical and psychological stress after exposure to trauma, and security vulnerabilities similar to Sworn Police Officers. The perceived availability of mental health resources, job-related physical, psychological stress, and traumatic experiences of both Forensic Technicians and Sworn Police Officers from California law enforcement agencies were investigated using a self-reported survey. Responses were evaluated for any significant differences in the perceived stress, job-related physical stress, and resulting psychological impact affecting the participants. The survey contained a mix of True/False, Circle/Check the Appropriate Box, or Likert Scale (1–5) responses. The results were evaluated statistically and discussed. Results indicated Sworn Police Officers and Forensic Technicians have different on-duty stress levels, but similar off-duty stress levels. Nearly two-thirds of 54 job-related stressors were not significantly different between the two occupations. However, Forensic Technicians reported more adverse effects in 17 physical and psychological job-related activities compared with Sworn Police Officers. Forensic Technicians reported lower awareness levels and availability of agency mental health support services than were reported by Sworn Police Officers. This study reports for the first time an unexpected outcome that perceived and job-related psychological stress is greater for Forensic Technicians than Sworn Police Officers. Possible reasons for this disparity will be discussed as well as stress management tools that should be implemented to reduce health risk factors for both career professionals as well as increase public safety.     

Improved Area of Origin Estimation for Bloodstain Pattern Analysis Using 3D Scanning

An important component of crime scene reconstruction is bloodstain pattern analysis (BPA). Where BPA concerns impact patterns, estimating the area of origin is critical information for scene reconstruction. Traditionally, this is achieved by measuring individual bloodstains and performing trigonometric calculations; however, 3D scanning has been proposed as a viable alternative for overcoming logistical and practical concerns with the manual method. Therefore, this project aimed to establish whether the FARO Focus 3D scanner and FARO Zone 3D software can improve the accuracy of area of origin estimates relative to the manual method. We created a series of eight bloodstain impact patterns and performed paired analysis using the two methods to estimate areas of origin for each pattern. Our data suggested that FARO-derived estimates were generally more accurate than using the manual method. FARO-estimated heights of origin areas were generally closer to the true distance. Both methods underestimated the distance from the wall for most patterns originating 150mm or greater from the wall, but overestimated distances for patterns originating closer to the wall. The degree to which distances were underestimated increased significantly the further the blood source was from the wall and was greater for FARO-derived estimates. The results of this research contribute to the validation of these instruments for operational implementation for BPA and should be considered alongside the practical benefits of 3D scanning relative to manual methods. Further, 3D scanning can provide reliable BPA reconstruction documentation for technical review and court presentation.     

现场勘查工作存在的主要问题及对策

现场勘查工作是案件侦查的起点和基础,是刑事诉讼活动的首要环节。现场勘查的成功与否关系到整个侦查工作的成败以及刑事诉讼活动能否顺利进行。目前,现场勘查工作存在领导重视不够、经费紧张、现场保护不到位、现场勘查指挥不力、侦查员与技术员缺乏沟通等问题,应采取如下对策：加强领导,加大投入,建立一支高素质的专业队伍;加大宣传力度,进一步做好现场保护工作：强化现场勘查指挥工作,确保勘查工作有序进行;强化侦查意识、证据意识,落实侦技结合的工作机制;健全管理制度,规范工作程序,等等。     

反劫持谈判战术误区(中)

警方谈判者缺乏现场预测能力、喜欢说教与恫吓、轻易同意现场交换人质是进入谈判低谷,谈判者无力摆脱劫持者在心理上的纠缠的一种最典型的反映。这种失利状态一旦发生,就极有可能导致谈判的全面失败．     

不同消毒方式对现场DNA检出影响研究

目的 探讨新型冠状病毒敏感的消毒方式对于常见现场生物物证如血、脱落细胞的检出影响,探索在疫情期间现场勘查、实验室检验及尸体解剖前后的合理消毒方式.方法 采用《消毒剂使用指南》推荐的几种不同浓度化学消毒剂和紫外线照射等方式,对常量的血、口腔拭子和稀释的血、唾液斑进行作用后的样本DNA检出情况进行对比.结果 常用消毒方式对...     

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。