利用铣纹痕迹数量和角度判断钢丝钳剪切位置

目的观察钳剪钢丝铣纹痕迹规律。方法用钢丝钳剪切铁丝,观察形成铣纹痕迹的特点和规律,并对铣纹痕迹数量和倾斜角度与钢丝钳剪切刃口位置的关系予以分析。结果钢丝钳刃口形成的铣纹痕迹数量和倾斜角度随刃口位置变动而发生相应变化。结论通过检测铣纹痕迹的数量和倾斜角度能可靠判断剪切刃口的具体位置,为制作样本选择刃口部位提供依据。     

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%.     

Quantitative Statistics and Identification of Tool‐Marks

This study was designed to establish a feature identification method of tool‐mark 2D data. A uniform local binary pattern histogram operator was developed to extract the tool‐mark features, and the random forest algorithm was adopted to identify these. The presented method was used to conduct five groups of experiments with a 2D dataset of known matched and nonmatched tool‐marks made by bolt clippers, cutting pliers, and screwdrivers. The experimental results show that the proposed method achieved a high rate of identification of the tool‐mark samples generated under identical conditions. The proposed method effectively overcomes the disadvantage of unstable illumination of 2D tool‐mark image data and avoids the difficulty in mark inspection caused by manually preset parameters in the existing methods, thus reducing the uncertainty of inspected results.     

从剪切痕迹区别钢丝钳种类

对不同产地的八个品牌钢丝钳的外刃侧加工花纹特征及其在剪切痕迹中的反映作了研究.总结出了各品牌钢丝钳特征的差异,达到了区分的目的.为钢丝钳种类推断提供了一种确实可行的方法.     

单芯电缆线断头痕迹实物提取方法

目的研究单芯电缆线这种离散型客体的实物提取方式、涉及的提取工具和最佳提取长度。方法采用模拟实验的方式,选用不同种类的单芯电缆线为客体,以电缆线断头痕迹不发生变化为基准,确定不同实物提取方式或不同种类工具提取单芯电缆线的最短长度。结果单芯电缆线实物提取可采取的方式主要有钳剪和割削两种,其中钳剪提取方式使用的工具为断线钳和线缆剪,割削提取方式使用的工具为钢锯和角磨机;针对直径小于16mm、非金属外护套及绝缘层的单芯电缆线,断线钳剪切提取最佳长度约为55cm,线缆剪剪切提取最佳长度约为70cm,钢锯锯割提取最佳长度约为5cm,角磨机切削提取最佳长度约为5cm。结论割削提取方法是提取电缆线断头的最佳方法;依据提取操作简便性及快捷性,角磨机(或充电式角磨机)为现场提取电缆线断头的最佳工具。     

断线钳剪切痕迹特征的实验研究

探讨断线钳剪切金属客体所形成的痕迹特征及其检验方法.     

Optimization of a Statistical Algorithm for Objective Comparison of Toolmarks

Due to historical legal challenges, there is a driving force for the development of objective methods of forensic toolmark identification. This study utilizes an algorithm to separate matching and nonmatching shear cut toolmarks created using fifty sequentially manufactured pliers. Unlike previously analyzed striated screwdriver marks, shear cut marks contain discontinuous groups of striations, posing a more difficult test of algorithm applicability. The algorithm compares correlation between optical 3D toolmark topography data, producing a Wilcoxon rank sum test statistic. Relative magnitude of this metric separates the matching and nonmatching toolmarks. Results show a high degree of statistical separation between matching and nonmatching distributions. Further separation is achieved with optimized input parameters and implementation of a “leash” preventing a previous source of outliers—however complete statistical separation was not achieved. This paper represents further development of objective methods of toolmark identification and further validation of the assumption that toolmarks are identifiably unique.     

Tool mark striations in pig skin produced by stabs from a serrated blade

Stab wounds produced by serrated blades are generally indistinguishable from stab wounds produced by non-serrated blades, except when visible tool mark striations are left on severed cartilage. Using a pig-skin experimental model, we explored the possibility that similar striations may be left in skin. Stabs into pig skin were made using a straight spine coarsely serrated blade (121), a drop point finely serrated blade (20), a clip point irregular coarsely serrated blade (20), a drop point coarsely serrated blade (15), and as controls 2 non-serrated blades (40). Tool mark striations could be seen on the skin wall of the stab canal in all stabs made using serrated blades but in none with non-serrated blades.The striation pattern, reflecting the class characteristics of the serrated blade, was the same as that described in cartilage but less well defined. Fixation of the specimen with Carnoy's solution best preserved visible striations, and fixation with formaldehyde after staining with 5% Neutral Red was also satisfactory. Casting with vinyl polysiloxane dental impression material greatly facilitated photo-documentation. Applying the technique to homicidal stabbings may help identify stab wounds produced with serrated blades.     

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.     

Quantitative analysis of sharp-force trauma: an application of scanning electron microscopy in forensic anthropology.

Scanning electron microscopy (SEM) has occasionally been used by anthropologists and forensic scientists to look at morphological characteristics that certain implements leave on bone. However, few studies have addressed techniques or protocols for assessing quantitative differences between tool marks on bone made by different bladed implements. In this study, the statistical variation in cut mark width was examined between control and test samples on bone using a scalpel blade, paring knife, and kitchen utility knife. Statistically significant differences (p < .0005) were found between cut marks made by the same knife under control and test conditions for all three knife types used in the study. When the control sample and test samples were examined individually for differences in mean variation between knife types, significant differences were also found (p < .0005). While significant differences in cut mark width were found, caution should be used in trying to classify individual cut marks as being inflicted by a particular implement, due to the overlap in cut mark width that exists between different knife types. When combined, both quantitative and qualitative analyses of cut marks should prove to be more useful in trying to identify a suspect weapon. Furthermore, the application of SEM can be particularly useful for assessing many of these features.     

Bolt Cutter Blade's Imprint in Toolmarks Examination

Bolt cutters are known as cutting tools which are used for cutting hard objects and materials, such as padlocks and bars. Bolt cutter blades leave their imprint on the cut objects. When receiving a cut object from a crime scene, forensic toolmarks examiners can determine whether the suspected cutting tool was used in a specific crime or not based on class characteristic marks and individual marks that the bolt cutter blades leave on the cut object. The paper presents preliminary results of a study on ten bolt cutters and suggests a quick preliminary examination—the comparison between the blade thickness and the width of the imprint left by the tool on the cut object. Based on the comparison result, if there is not a match, the examiner can eliminate the feasibility of the use of the suspected cutting tool in a specific crime. This examination simplifies and accelerates the comparison procedure.     

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。     

Development of a Mobile Toolmark Characterization/Comparison System

Since the development of the striagraph, various attempts have been made to enhance forensic investigation through the use of measuring and imaging equipment. This study describes the development of a prototype system employing an easy‐to‐use software interface designed to provide forensic examiners with the ability to measure topography of a toolmarked surface and then conduct various comparisons using a statistical algorithm. Acquisition of the data is carried out using a portable 3D optical profilometer, and comparison of the resulting data files is made using software named “MANTIS” (Mark and Tool Inspection Suite). The system has been tested on laboratory‐produced markings that include fully striated marks (e.g., screwdriver markings), quasistriated markings produced by shear‐cut pliers, impression marks left by chisels, rifling marks on bullets, and cut marks produced by knives. Using the system, an examiner has the potential to (i) visually compare two toolmarked surfaces in a manner similar to a comparison microscope and (ii) use the quantitative information embedded within the acquired data to obtain an objective statistical comparison of the data files. This study shows that, based on the results from laboratory samples, the system has great potential for aiding examiners in conducting comparisons of toolmarks.     

6种现场常见断线钳加工特征的研究

目的研究不同品牌断线钳加工特征的差异性及痕迹反映与加工特征之间的关系。方法以6种现场常见断线钳为研究对象,首先观测断线钳的刃顶厚度、刃片咬合间隙、刃侧铣纹宽度和铣纹间距等参数,然后观测剪切断头痕迹的立顶高度、立顶厚度、刃侧铣纹印痕宽度和铣纹印痕间距等参数,并用SPSS统计软件进行处理。结果 6种品牌的断线钳加工特征存在差异,断头痕迹可以稳定地反映该差异。结论可利用断头痕迹特征推断断线钳种类。     

Chronology of a homicide and an attempted suicide by DNA analysis of selected blood stains on the weapon (knife)]

A five-year-old boy was fatally injured by a stab and a cut to the throat. The suspected offender, an acquaintance of the victim's mother, stated that he had been disturbed by the boy while attempting suicide and had therefore killed the boy. The suspect showed superficial cuts on both wrists and three shallow stabs on the right-hand side of the abdomen. The purpose of the forensic investigations was to answer the question if the suspect's statement could be confirmed or if the attempted suicide took place after killing the boy. The blood-smeared blade of the knife was divided into different sectors with the cutting edge and the tip of the blade being examined separately from the sides. The blood traces from the different blade sectors were then typed in 12 different DNA regions by PCR (polymerase-chain-reaction). It could be demonstrated that the strong blood traces on the sides of the blade originated from the victim alone, whereas in the area of the edge and the tip of the blade the amount of the victim's blood was negligible compared with that of the suspected offender. The explanation for this finding is that in the areas of the edge and the tip of the knife the blood of the victim must have been replaced by the blood of the suspected perpetrator, which means that the suicidal injuries were the last to be caused by the knife.     

An experimental model of tool mark striations in soft tissues produced by serrated blades

Stab wounds produced by serrated blades are generally indistinguishable from stab wounds produced by non-serrated blades, except when visible tool mark striations are left on severed cartilage. We explored the possibility that similar striations may be produced on the soft tissues of internal organs. Loin of beef, bovine kidney, and pig heart, liver, and aorta were each stabbed 20 times with a coarsely serrated blade. The walls of the stab tracks were exposed and documented by photography, cast with dental impression material, and the casts photographed. Striations were identified in all of the tissues in every stabbing, but their consistency and quality varied between tissues. Striations were most easily seen in liver, heart, and aorta. Tool mark striations in soft tissues other than cartilage have not been described in homicidal stabbings, likely because they have not been sought. We suggest that the walls of stab wound tracks should be exposed, and tissue striations should be sought as a means of identifying the weapon as having a serrated blade.     

非对等咬合钳具形成痕迹特点的研究

根据大量的实验事实,通过材料的变形分析,对非对等咬合的钳类工具所形成的痕迹进行研究,阐述了不同坡面上的变形性质和痕迹特点,总结了痕迹与工具的对应关系,为工作实践指出了分析和检验鉴定的方法,同时对钳类工具痕迹的形成原理作出了补充和修正。     

Identification of Tool Marks of a Sickle on a Telephone Cable

Linkage of a cutting tool (a sickle) with a telephone cable of 100 pairs of copper wires is reported in a case of theft of a telephone cable. Telephone cables contain numerous insulated copper wires of small diameter inside an outer covering and are stolen for the relatively precious copper. The cutting pattern of the cable can only point to the type of the tool but because of the large number of copper wires, it is practically difficult to make a definite linkage with the tool used to cut the cable by comparing the tool marks. The present work reports the successful attempt of the authors in establishing a definite linkage of a stolen telephone cable with a sickle recovered from the suspects. Spot microchemical test was performed for detection of copper on the blade of the sickle, and then tool mark comparison was performed to link the tool marks on the metal strip inside the outer covering of the cable to the blade of the sickle.     

Deep incisional neck injuries caused by an electric knife

Electric knives, due to the double blades swinging in opposite directions, have a high injury potential. Tissues such as skin can be cut smoothly without cutting motion and with only little pressure. Authors report on the case of a woman of 47 years who cut herself deeply on both sides of her neck with an electric knife, slightly carving a notch into the larynx and a cervical vertebra and opening large blood vessels. With respect to the extent of injuries the capacity to act had to be questioned. However, considering the absence of venous air embolism and the peculiarity of the tool it had to be assumed that the capacity to act lasted for a short time.     

Microscopic characteristics of hacking trauma

The purpose of this study was to determine if it is possible to associate machetes, axes, and cleavers with the microscopic parallel striations they leave on the cut surfaces of the bone. Hacking trauma was experimentally inflicted on pig bones using machetes, axes, and cleavers. Negative impressions of both the cut surfaces of the bone and the weapon blades were analyzed using scanning electron microscopy. The results of this investigation indicate that it is possible to correlate a class of hacking weapons to trauma inflicted on bone by these weapons.