凸齿钥匙上仿形刀痕迹倾斜角与齿坡角的关系初探

目的探索被增配凸形钥匙上仿形刀痕迹倾斜角度与齿坡角间的关系。方法用铝板制作相同坡长不同齿坡角的钥匙模型，在相同夹持方式下模拟增配过程，观察并总结钥匙上仿形刀痕迹倾斜角度的变化。结果不同齿坡角上仿形刀痕迹倾斜角度不同。结论凸齿钥匙上仿形刀增配痕迹倾斜角度随齿坡角的增大而减小。     

曲形槽状齿钥匙被增配痕迹的实验研究

目的 探索曲形槽状齿钥匙上的增配痕迹特征及其随开启次数的变化.方法 用被增配过的原配钥匙进行模拟开锁实验,观察开启前后的增配痕迹.结果 发现原配钥匙上的增配痕迹主要为钥匙板侧上的夹持痕迹和齿槽底面、齿槽壁上的擦划痕迹,且齿底面上的擦划痕迹随开启次数增加较稳定,齿壁上的擦划痕迹随开启次数增加呈渐变性变化.结论 原配钥匙上的增配痕迹主要为夹持痕迹和仿形针擦划痕迹,夹持痕迹反映不明显,仿形针擦划痕迹较稳定.     

材质硬度对凸齿原配钥匙增配夹持痕迹的影响

目的探讨材质硬度对凸齿原配钥匙增配夹持痕迹的影响。方法测试铁、铜、铝3种材质钥匙的硬度后,分别在配匙机上增配3种材质的钥匙,观察原配钥匙上的夹持痕迹。结果 3种材质钥匙上的增配夹持痕迹有较大区别。结论不同硬度的凸齿钥匙上增配夹持痕迹的反映性不同。     

钥匙上复制痕迹的检验要点

1 钥匙被复制形成的痕迹类别钥匙被复制形成的痕迹是指在增配钥匙时,配匙机器的有关部件作用于匙模上形成的形态变化,其分为固定夹板的夹待印压痕和定位刀的刮划痕两种.匙模,是指用来当作模型的钥匙,它既可以是原配钥匙,也可以是后配钥匙.1.1 夹持印压痕:位于匙体两侧面,是固定夹板对钥匙匙体的两侧面同时施加对向正压力而形成.痕迹呈长条带状,平行于钥匙轴线,新鲜痕迹反映较好,痕迹发亮,略有发毛.     

内凹齿钥匙痕迹特征研究

目的运用光学仪器研究内凹齿钥匙痕迹形态特征。方法制作内凹齿钥匙正常开锁和被钥匙机复制后的样本,用光学显微镜拍照固定痕迹特征。结果内凹齿钥匙开锁痕迹特征明显,且被钥匙机复制后能留下复制痕迹。结论通过检验内凹齿钥匙上的痕迹特征能确定钥匙是否被复制过。     

方形坡状齿钥匙增配痕迹的实验研究

目的探索方形坡状齿钥匙增配痕迹形成规律、增配痕迹随开启次数的渐变过程以及增配痕迹的变化因素。方法用被增配过的原配钥匙和增配钥匙进行模拟开启实验，观察并记录开启前和开启过程中的增配痕迹。结果被增配钥匙的坡面上有明显的印压痕迹和擦划痕迹，增配痕迹随开启次数增加呈渐变性变化，且原配钥匙和增配钥匙上的增配痕迹变化不同。结论增配痕迹为印压痕迹和擦划痕迹，印压痕迹随着开启次数增加而逐渐消失，擦划痕迹较稳定。     

月牙槽状齿钥匙增配痕迹的实验研究

目的探索月牙槽状齿钥匙增配痕迹形成规律、增配痕迹随开启次数的渐变过程以及影响增配痕迹的变化因素。方法用被增配过的原配钥匙进行模拟开锁实验,观察并记录开启前和开启过程中的增配痕迹。结果被增配钥匙的齿面上有明显的磕碰痕迹和擦划痕迹,增配痕迹随开启次数增加呈渐变性变化,且不同区域的增配痕迹变化不同。结论月牙槽状齿钥匙的被增配痕迹为磕碰痕迹和擦划痕迹,齿槽壁上的被增配痕迹随着开启次数增加较稳定。     

推断工具种类1例

钳剪形成的夹持痕迹,往往会出现对称的钳剪刃口痕迹或夹持面平台及齿纹痕迹,很少会同时出现夹持面后平台和钳剪刃口痕迹。笔者曾遇到一起夹持面     

钢丝钳夹持面痕迹形成特点与检验

在犯罪现场特别是盗窃现场和破坏通讯线路、通讯电缆等现场,经常有用钢丝钳作案后留下的痕迹。在不少文献中对钢丝钳的种类规格和钳剪痕迹的检验鉴定的论述。但对钢丝钳其它部位留下痕迹的检验报道较少,本文着重讨论钢丝钳夹持面痕迹形成的特点与检验。1钢丝钳夹持面的一般特点钢丝钳夹持面,是指从钢丝钳钳嘴起到夹圆体口止的部位。夹持面包括:钳嘴、前平台齿纹和后平台(有些厂家生产的钢丝钳无后平台)3个部分组成。夹持面因规格大小和生产厂家不同,在齿数、齿距、前后平台的宽度,钳嘴长度也不同。常见的几种规格钢丝钳夹持面的齿纹数,一般…     

后配钥匙的检验及鉴别

后配钥匙是借助于手工或机械锉、铣加工复制,齿列关系与原配钥匙相一致的新钥匙。而对用后配钥匙做案案例的研究,往往偏重于后配钥匙在锁芯弹子上形成的痕迹和原配钥匙在复制过程中形成痕迹的分析、研究,最能反映加工复制痕迹的后配钥匙常常被忽视。对其进行科学地分析和检验、识别原配或后配钥匙,这在实践工作中具有很大的应用价值。 1 后配钥匙上复制加工痕迹及其形成机理 后配钥匙一般是使用匙坯加工复制而成的,开齿过程中在钥匙坯上会形成明显的加工痕迹。后配钥匙上的加工痕迹主要有以下5种。     

The Influence of Wood Grain on the Bullet's Ricochet Behavior

When a bullet ricochets from wood, various parameters will influence its behavior. In this study, the influence of the wood grain on the ricochet angle (β) and deflection angle (γ) is assessed. Series of five .32 Auto bullets were fired at different angles of incidence (α) on boards of six wood types. The results confirm the previously shown effect that the mean β‐angles usually exceed α and increase when α increases. Overall, the maximum mean γ occurs when the angle of wood grain (ζ), in relation to the plane of impact, lies between 30° and 75° but differs per combination of wood and α. The results show the inclination of γ toward the left or right, depending on the bullets left or right rotation while also showing that the direction of ζ can enhance or counteract this effect considerably, especially when α is close to the critical ricochet angle.     

The influence of a shot distance on a profile of a wound canal in flat bones

Experimental shots were made from rifled weapons, from different distances, at isolated flat bones. There was established a significantly increased angle of the axial section of the cone-shaped defect due to the expanding sizes of the exit part of the wound canal (WC) and of the outlet opening as the shot distances increased. An expert's evaluation is offered to assess a shot distance involving the WC profile and by calculating an angle of the axial section of the cone-shaped defect on the basis of the inlet and outlet sizes and of the flat-bone thickness.     

The systemic error in the vertical component of handgun bullet trajectory reconstructions

Establishing the path or trajectory of a fired bullet is an often recurring part of shooting incident reconstruction. The current study describes how gravitational pull causes a systemic error on the vertical component of a trajectory reconstruction. Bullet drop, drop angle, and vertical offset are explained and calculated for 10 different handgun/ammunition combinations over a range of distances up to 100 m. The presented results are intended to provide forensic firearm examiners with a reference frame for the magnitude of error introduced on handgun bullet trajectory reconstructions over distance. Threshold values of 20 and 30 m are proposed as conservative distances up to where bullet trajectories can be modeled as straight lines with subsonic/transonic handgun bullets and with supersonic handgun bullets respectively. Both the bullet drop and vertical offset will be below 5 cm at these distances for those categories. The drop angle will be below 0.3°.     

Digital analysis of experimental human bitemarks: application of two new methods

Bitemark determination in forensic odontology is commonly performed by comparing the morphology of the dentition of the suspect with life-sized photographs of injury on the victim's skin using transparent overlays or computers. The purpose of this study is to investigate the suitability of two new different methods for identification of bitemarks by digital analysis. A sample of 50 volunteers was asked to make experimental bitemarks on the arms of each other. Stone study casts were prepared from upper and lower dental arches of each volunteer. The bitemarks and the study casts were photographed; the photos were entered into the computer and Adobe Photoshop software program was applied to analyze the results. Two methods (2D polyline and Painting) of identification were used. In the 2D polyline method, fixed points were chosen on the tips of the canines and a straight line was drawn between the two fixed points in the arch (intercanine line). Straight lines passing between the incisal edges of the incisors were drawn vertically on the intercanine line; the lines and angles created were calculated. In the painting method, identification was based on canine-to-canine distance, tooth width and the thickness, and rotational value of each tooth. The results showed that both methods were applicable. However, the 2D polyline method was more convenient to use and gave prompt computer-read results, whereas the painting method depended on the visual reading of the operator.     

内、外铣槽钥匙机械配制痕迹的研究

目的研究内、外铣槽钥匙机械配制后痕迹的出现规律及其影响因素。方法利用传统的痕迹检验方法观察痕迹出现的位置、形态及分布规律。结果内、外铣槽钥匙机械配制后会留下不同于其原始加工痕迹和使用痕迹的增配痕迹，这种痕迹是否明显出现、出现的形态和位置受钥匙材质和结构、配匙机、配匙人员工作经验等因素的影响。结论当未发现内、外铣槽钥匙上有明显增配痕迹时，不能轻易做出钥匙未被增配的判断。     

Errors in the estimation of the distance of fall and angles of impact blood drops.

This paper presents derived equations for the estimation of the variances in the estimated distance of fall and the estimated angle of impact for blood droplets. The derived equation for the variance of the estimated distance of fall predicts that as the blood drop size approaches that of a blood droplet falling at terminal velocity, the variance of the estimate grows without limit. The derived equation for the variance in the estimated angle of impact shows that as the angle of impact approaches 90 degrees, the variance grows without limit. The validity of the equation for the estimated variance of the angle of impact was tested for five angles of impact (15, 30, 45, 60 and 75 degrees); the equation correctly predicted the observed variance up to an angle of 60 degrees.     

Pedestrian accident analysis with a silicone dummy block

When a car is parked in an inclined plane in a parking lot, the car can roll down the slope and cause a pedestrian accident, even when the angle of inclination is small. A rolling car on a gentle slope seems to be easily halted by human power to prevent damage to the car or a possible accident. However, even if the car rolls down very slowly, it can cause severe injuries to a pedestrian, especially when the pedestrian cannot avoid the rolling car. In an accident case that happened in our province, a pedestrian was injured by a rolling car, which had been parked on a slope the night before. The accident occurred in the parking lot of an apartment complex. The parking lot seemed almost flat with the naked eye. We conducted a rolling test with the accident vehicle at the site. The car was made to roll down the slope by purely gravitational pull and was made to collide with the silicone block leaning against the retaining wall. Silicone has characteristics similar to those of a human body, especially with respect to stiffness. In the experiment, we measured the shock power quantitatively. The results showed that a rolling car could severely damage the chest of a pedestrian, even if it moved very slowly.