现场痕迹剔除中的综合分析

在实际工作中,我们应注意区分在犯罪现场提取到的指纹,足迹等痕迹是犯罪痕迹还是非犯罪痕迹,认真做好剔除。剔除和认定同一,在痕迹检验中同样重要,两者相辅相承,缺一不可。认定同一的前提,首先是做好剔除;而剔除的目的,就是为了确定犯罪痕迹,进行认定同一。实践中,一般是先剔除当事人、被害人及家属,以及可能接触过现场而留有痕迹但与犯罪无关的人,而后确定犯罪痕迹。但要注意,有些痕迹即使是事主或其他平时可能接触的人所留,亦不该笼统地排除其嫌疑,而应对现场痕迹进行仔细观察研究和综合分析。不但要研究痕迹本身,研究痕迹在现场中的位置及其与其他物体之间的相互联系,还要结合研究现场访问材料,进行综合分析,才能作出符合实际的最后判断。一、认真做好现场勘验,是痕迹剔除的关键所在。1.研究痕迹的形成过程。痕迹的形成与作案人的心理、动作习惯、入侵方式,作案的目的动机,障碍物的高低,物体的形状等紧密联系。在勘查中要注意研究痕迹的形成过程,这样对分析案情,确定案件性质,确定犯罪痕迹和非犯罪痕迹具有非常重     

纸张客体裁切整体分离痕迹同一认定中的陷阱

纸张是日常生活和工作等方面的必需品,经常作为书证载体或物证出现在案件中。有时为了查清破碎纸片的来源,需要对物证纸张与涉嫌纸张进行整体分离同一认定,确认物证纸张与涉嫌纸张是否同一张纸分离形成的。纸张整体分离痕迹同一认定方法与其它物体整体分离痕迹认定方法大同小异,不外乎寻找凸起点与凹陷点,并进行对应拼接,吻合则说明是同一张纸裁切分离形成的,不吻合则是不同纸。2002年3月,某国家机关纪委查处本单位一位干部涉嫌贪污案件,该干部提供对方单位业务联系人出具的现金收条4份,但对方业务联系人不承认收过现金打过收条,并称所有货…     

人体骨骼上菜刀痕迹的检验及同一认定

目的 对人体骨骼上刀痕进行致伤工具同一认定的检验和研究.方法 用同一把菜刀的相同部位分别砍击骨骼与新鲜灌木,通过对骨骼上刀痕进行组织学处理以显现致伤工具的痕迹,并使用比对显微镜将骨骼与灌木上的砍痕进行比对,分析骨质断面的痕迹特征.结果 菜刀在骨骼上形成的砍切痕迹线条与比对样本的砍切痕迹线条可以完全拼接.结论 显微镜下可直观、清晰地观察到致伤工具在骨骼上留下的痕迹,为致伤工具的推断提供了新的方法.     

枪弹痕迹情报网络共享与交换

枪弹痕迹的远程会商,是利用计算机网络基础设施,采用多种网络多媒体技术,集中枪弹痕迹同一认定所需要的特征参数及有关资料,约请专家在网络上进行商讨,就某一案件枪弹痕迹同一认定,得出明确结论的一种新的工作方式。枪弹痕迹的远程会商能否实现,其很大程度取决于对枪弹痕迹鉴定本质的认识。为此,必须对枪弹痕迹的特征进行分类,并对每一类痕迹所能具备的鉴定价值属性进行确认。根据枪弹痕迹的形成机理、部位以及各特征层次的不同属性,可以确定主要将弹底痕迹特征中的击针头痕迹、后膛加工纹痕迹、抛壳挺痕迹作为枪弹痕迹远程会商系统工作的主…     

发射弹头痕迹特征的形成变化机理及应用

由于各种枪械的机件特征不同,枪支发射时将在弹头上留下反映枪械机件特点的种类及特定特征。通过研究枪械生产制作和使用过程中其部件特征形成的基础上,从弹道学原理入手,分析了枪支发射过程中弹头痕迹形成的机理和痕迹特征的变化因素,为枪支同一认定鉴定中检材与样本特征产生差异的原因分析及得出可靠的鉴定意见提供了科学的理论依据和实践方法。     

发射弹头痕迹特征的形成变化机理及应用

由于各种枪械的机件特征不同,枪支发射时将在弹头上留下反映枪械机件特点的种类及特定特征.通过研究枪械生产制作和使用过程中其部件特征形成的基础上,从弹道学原理入手,分析了枪支发射过程中弹头痕迹形成的机理和痕迹特征的变化因素,为枪支同一认定鉴定中检材与样本特征产生差异的原因分析及得出可靠的鉴定意见提供了科学的理论依据和实践方法.     

断线钳剪切链锁形成痕迹的研究

链锁是一种较为常见的安全防护锁具。破坏链锁实施盗窃犯罪,在侵财案件中较为常见。但当前对于断线钳剪切链锁形成的痕迹还缺少专门性的研究。因此,对于链锁剪切痕迹的研究、分析、利用,有其必要性。本文通过对其痕迹的研究,以期掌握此类痕迹的形成、变化规律,对推断工具种类,准确的进行同一认定具有重要意义。     

订书钉上痕迹的检验及鉴定

订书钉作为一种装订材料,被订书机打入文件等纸张上起固定作用。在打入过程中,订书机刀片是否会在订书钉背面留下痕迹,以及留下的痕迹有无检验条件,可否利用上述痕迹进行订书机的同一认定等等问题,此前未见报道。本文从订书钉、订书机的生产、使用方面进行了实验分析。     

液压断线钳与普通断线钳剪切痕迹的检验及应用

目的通过研究不同类型、规格和功能断线钳所形成剪切痕迹的异同,准确的进行工具痕迹的同一认定。方法运用实验观察法,比较法对液压断线钳与普通断线钳形成痕迹特征反映的异同进行分析。结果液压断线钳与普通断线钳从结构特征、剪切痕迹特征反映等方面存在着明显的差异。结论在对剪切痕迹的检验中,需要注意从被剪断头的材质、直径、断端形状等方面着手,区别不同种类的剪切工具,尤其要注重对实验样本的制作,这样才能充分发挥剪切痕迹在侦查破案中的证据作用。     

耳纹痕迹的同一认定

耳纹痕迹的同一认定是一个较新的研究领域,虽然目前吸引了众多法庭科学专家的关注,但在同一认定的诸多方面还没有达成共识,研究者们仍处于独立探索和相互讨论之中。从耳纹痕迹同一认定的理论基础、认定程序、测量体系、计算机识别这四个方面入手,分别介绍了此项研究存在的问题及取得的进展。     

Virtual casting of stab wounds in cartilage using micro-computed tomography

In homicidal stabbings using a serrated knife, stab wounds involving costal cartilage leave striations on the cut surface of the cartilage from the serration points on the blade edge. Class characteristics of the serrated blade can be determined from the striation marks, and individualizing characteristics may be seen also. The traditional method for recording the striation marks involves the pernickety technique of casting with dental impression material. We assessed the potential utility of micro-computed tomography scanning of the stab track as a technique for nondestructive recording of striation patterns and virtual casting of them. Stab tracks in porcine cartilage, produced with a coarsely serrated blade, were scanned with a bench-top micro-computed tomography scanner. The typical irregularly regular striation pattern could be demonstrated, and the images manipulated, using proprietary software to produce a virtual cast. Whether the technology will have sufficient resolution to image not only class characteristic tool marks but also the much finer individualizing tool marks remains to be evaluated, but the technology shows considerable promise.     

Striation Density for Predicting the Identifiability of Fired Bullets with Automated Inspection Systems*

Abstract: Automated firearms identification systems will correlate a reference bullet with all evidence bullets without a selection procedure to exclude the bullets having insufficient bullet identifying signature. Correlations that include such bullets increase the workload and may affect the correlation accuracy. In this article, a parameter called striation density is proposed for determining and predicting bullet identifiability. After image preprocessing, edge detection and filtering techniques are used to extract the edges of striation marks, the resulting binary image distinctly shows the amount and distribution of striation marks. Then striation density is calculated for determining the quality of images. In the experiment, striation densities for six lands of 48 bullets fired from 12 gun barrels of six manufactures are calculated. Statistical results show strong relation between striation density and identification rate. It can provide firearms identification systems with a quantitative criterion to assess whether there are sufficient striae for reliable bullet identification.     

Validation of tool mark analysis of cut costal cartilage

This study was designed to establish the potential error rate associated with the generally accepted method of tool mark analysis of cut marks in costal cartilage. Three knives with different blade types were used to make experimental cut marks in costal cartilage of pigs. Each cut surface was cast, and each cast was examined by three analysts working independently. The presence of striations, regularity of striations, and presence of a primary and secondary striation pattern were recorded for each cast. The distance between each striation was measured. The results showed that striations were not consistently impressed on the cut surface by the blade's cutting edge. Also, blade type classification by the presence or absence of striations led to a 65% misclassification rate. Use of the classification tree and cross-validation methods and inclusion of the mean interstriation distance decreased the error rate to c. 50%.     

Automated comparison of firearm bullets

Fired bullets bear striation marks that can be thought of as a "fingerprint" left by the firearm. This new comparison approach is based on an automated extraction of a "signature" encompassing the relevant marks from an image. To this end, multiple pictures of the bullet are recorded first by using different illumination patterns, and a high quality image is generated by means of fusion techniques. After a preprocessing, the image intensities are filtered along the striations direction, yielding a compact representation of the marks. A non-linear filter selects the striae of interest. The actual comparison takes place by cross-correlating the signatures obtained this way. Finally, an assessment strategy is proposed to objectively evaluate the performance of the system. As demonstrated with an image database of real bullets, the proposed approach outperforms a state-of-the-art commercial system.     

Improve Toolmarks' Impressions in Soft Wax

When the forensic toolmarks laboratory receives for examination and comparison a tool that is suspected of having been involved in a crime, the expert performs tests designed to determine whether or not the specific tool generates the same toolmarks as those found at the crime scene. This is performed by testing tool striation on a piece of soft metal, such as lead, and examining the marks left by the tool. Studies have shown that wax may be an optimal material for this purpose. This study examines the use of wax at different temperatures and shows that quality of results is better when the wax is cooled (recommended temperature is ?18°C). At this temperature, the wax is flexible enough but does not smear and is not sticky. This makes the obtained marks clearer and of better quality.     

Striation patterns in serrated blade stabs to cartilage

Stab wounds were made in porcine cartilage with 13 serrated knives, amongst which 4 were drop-point and 9 straight-spine; 9 coarsely serrated, 3 finely serrated and 1 with mixed pattern serrations. The walls of the stab tracks were cast with dental impression material, and the casts photographed together with the knife blades for comparison. All 13 serrated blades produced an "irregularly regular" pattern of striations on cartilage in all stabbings. Unusual and distinctive blade serration patterns produced equally distinctive wound striation patterns. A reference collection of striation patterns and corresponding blades might prove useful for striation pattern analysis. Drop-point blades produced similar striations to straight-spine blades except that the striations were not parallel but rather fan-shaped, converging towards the wound exit. The fan-shaped striation pattern characteristic of drop-point blades is explained by the initial lateral movement of the blade through the cartilage imposed by the presence of the drop point shape. It appears that the greater the overall angle of the drop point, the shorter the blade length over which the drop point occurs, and the closer the first serration is to the knife tip, the more obvious is the fan-shaped pattern. We anticipate that micro-irregularities producing individualising characteristics in non-serrated drop point blades, provided they were located at the tip opposite the drop point, should also show a fan-shaped pattern indicative of a drop point blade. The examination of the walls of stab wounds to cartilage represents an under-utilised source of forensic information to assist in knife identification.     

通过痕迹认定肇事车辆

随着交通事故勘验技术的发展,物证技术在重特大交通事故现场勘验以及侦破交通逃逸案件中发挥的作用越来越重要.痕迹检验技术作为物证技术的一个重要分支,在认定肇事车辆中发挥着举足轻重的作用.交通事故中的痕迹是车辆与车辆、人体、道路等客体在路面上相对高速运动形成的痕迹,相对于其它类型案件有着自己的特点.交通事故中的痕迹分布范围广、造痕体和承痕体相对运动剧烈,形成痕迹的造痕体和承痕体大多都会发生形变.基于交通事故中痕迹形成的这些特点,交通事故中的痕迹检验难度是比较大的.但交通事故中车辆的特殊结构形成的印压痕迹、车辆轮胎、摩托车车篮等造痕体在灰尘等介质作用下在人体的衣服等表面形成的印压痕迹都可以很好反映造痕体的外部结构特征,从这些痕迹反映出造痕体的外部结构特征可以寻找和认定交通肇事车辆.     

The examination of disc and pin tumbler locks for tool marks made by lock picks.

Microscopic examination of the tumblers of pin and disc tumbler lock cylinders may indicate whether an attempt has been made to pick the lock. If an attempt has been made to pick the lock, it is often possible to determine what type of pick was used. Lock cylinders of five manufacturers, employing tumblers of several different compositions, were examined. The lock cylinders were picked with rake, hook, and bounce picks made of spring steel. The cylinders were disassembled and examined for pick marks. The location and appearance of the marks are discussed. Briefly mentioned are the effects of other types of picks and the effect of ball bearings in the pin wells. Photographs are included to show the pick and wear marks.     

A suggested classification of bite marks in foodstuffs in forensic dental analysis

Bite marks have been reported in flesh, foodstuffs and inanimate objects. Those in foodstuffs occur widely in cases of larceny but also occur in serious crimes such as murder.Evaluation of distinctive characteristics in food bites differs from the corresponding assessment of flesh bite marks in that the assessment is made on the impression made by the labial aspect of the teeth and not on the biting edge, because the teeth penetrate the bitten foods to different depths.The terminology used to describe food bite marks is very varied and a classification of food bites has been formulated in an effort to bring a degree of uniformity to the analysis of such marks.