An Empirical Study on the Relation Between the Critical Angle for Bullet Ricochet and the Properties of Wood

The properties of a bullet, an object, and the incidence angle determine whether the bullet will penetrate, perforate, or ricochet. In this study, the critical angle for ricochet was established for .32 Auto and 9 mm Luger bullets on Abachi, Southern Yellow Pine, Beech, and Ipe wooden boards. Results show that the critical angle differs depending on caliber and wood type. The critical angle is higher for .32 Auto bullets than for 9 mm Luger bullets and increases with increasing wood density and Janka hardness. The established critical angles for ricochet on the lightest and softest wood (Abachi) are 10.4° and 10.3° for .32 Auto and 9 mm Luger, respectively. For the heaviest and hardest wood (Ipe), the angles were 45.0° and 33.4°, respectively. The combined results on the four tested woods show a strong linear relationship between both the density and the hardness and the critical angle for both calibers.     

浅谈警察的应用射击

公安民警射击训练的实际出发,利用"威氏"射击法,提高命中效果控制紧张情绪,解除心理压力,掌握据抢要领,打牢射 击基础,克服外界影响,提高射击精度。     

浅谈警察手枪实用射击和互动战术射击

警察手枪实用射击和警察手枪互动战术射击是我国引进国外警察的两种手枪射击训练手段和竞赛方法。其训练内容设置合理 ,并且能根据各种具体实战情况制定训练方法 ,是提高公安民警射击水平和实践能力的有效途径     

浅谈公安民警射击技能训练的构思

维护社会治安,保障公共安全,预防控制犯罪,打击敌对势力和各种犯罪活动是公安队伍的基本职能。多年来,许多公安民警在打击和制止各种犯罪行为的斗争中流血牺牲,充分体现了他们对党和人民的忠诚和无私无畏的精神。同时,我们也应该认识到,有些伤亡原本是可以避免的。     

论对特殊被害人的刑法保护—以我国刑法第254条、255条之规定为视角

所谓特殊被害人,即我国刑法第254条、255条规定的遭受打击报复、陷害等犯罪行为的控告人、申诉人、批评人、举报人、会计人员、统计人员等六种被害人员。当前,这六种人员在履行职责、维护正义、维护国家、集体、自身利益时,其中的部分人时常遭到打击报复、陷害,人身权利和民主权利得不到保障。造成这一现象的原因固然众多,然而刑法第254条、255条规定之缺陷为重要缘由,因为对特殊被害人的刑法保护在法律上主要体现为刑法第254条、255条之规定。因此,为加强对特殊被害人的刑法保护,尽快完善这两条已成当务之急。     

Implementation and Optimization of the Sodium‐Rhodizonate Method for Chemographic Shooting Distance Estimation

In shooting incident investigations where it is important to estimate the shooting distance, the sodium‐rhodizonate coloring method has been used for the visualization of GSR patterns extensively. This publication describes the optimization of this method by the use of a heated press for the transfer of GSR traces on garments, as well as variation of a number of other important process parameters. Our final aim for this project was to prepare a formal validation of the coloring method as prerequisite for its inclusion into the scope of ISO17025‐certified methods in the GSR Laboratory. A number of important factors and process parameters were identified, such as buffer composition and pH, type of textile used as a substrate and resolution of the documentation of the results. Results were tested using a synthetic proficiency test. Our optimized method has been found to be a very effective technique for visualization of macroscopic GSR traces.     

Accuracy and Repeatability of Trajectory Rod Measurement Using Laser Scanners

Three‐dimensional (3D) technologies contribute greatly to bullet trajectory analysis and shooting reconstruction. There are few papers which address the errors associated with utilizing laser scanning for bullet trajectory documentation. This study examined the accuracy and precision of laser scanning for documenting trajectory rods in drywall for angles between 25° and 90°. The inherent error range of 0.02°–2.10° was noted while the overall error for laser scanning ranged between 0.04° and 1.98°. The inter‐ and intraobserver errors for trajectory rod placement and virtual trajectory marking showed that the range of variation for rod placement was between 0.1°–1° in drywall and 0.05°–0.5° in plywood. Virtual trajectory marking accuracy tests showed that 75% of data values were below 0.91° and 0.61° on azimuth and vertical angles, respectively. In conclusion, many contributing factors affect bullet trajectory analysis, and the use of 3D technologies can aid in reduction of errors associated with documentation.     

Controversial Suicide Case Using a Submachine Gun with a Sound Suppressor—The Need of Team Work of Forensic Chemistry and Firearm Examiners

Evidence materials in a presumed suicide case were studied by a firearm examiner and a forensic chemist. The victim's body with double gunshot wounding in his forehead, a machine gun in the sustained fire mode with a silencer, and four cartridge cases were found. Examinations of the evidence, the case file studies, and experiments dedicated to the case were carried out. Relationships between the placement of cartridge cases and the gun were established using a fast camera. The distributions of gunshot residues on the evidence materials and within the comparative gunshot patterns were studied by means of optical and electron microscopy, X‐ray microanalysis, and infrared spectroscopy. The shooting distance was assessed to be 30 cm or more, whereas the greatest distance that could have been achieved by the victim himself was about 11–13 cm. The obtained results supported the version of homicide rather than suicide.     

Crime and Philanthropy: Prosocial and Antisocial Responses to Mass Shootings

ABSTRACT

Mass shootings have a strong impact on public discourse and perception, affecting more than their direct victims. We use data on charitable contributions and criminal activity in the U.S. over the last decade to identify and quantify the effect of mass shootings on prosocial and antisocial behavior. We find that the effect of mass shootings on prosocial behavior, measured primarily by monetary contributions, is positive and statistically significant. However, the directly affected localities react to mass shootings differently than their neighboring communities, decreasing their charitable contributions. Additionally, we are unable to find a statistically significant effect of mass shootings on antisocial behavior, as measured by various crime rates. Furthermore, we show that mass shootings are different than any other type of criminal behavior, including all other violent offenses, in terms of its effect on prosocial behavior.     

The effects of physical effort on police officers' perception and aggression in simulated shooting incidents

Abstract

In the present experiment the effects of physical effort on police officers' aggression and perception in simulates shooting incidents were investigated. Based upon Kahneman's (1973) variable-allocation capacity model it was hypothesized that physical effort will result in a decease in aggression towards aggressive offenders. Based upon Kahneman's model and Easterbrook's (1959) Cue-Utilization-Hypothesis it was further expected that this decrease in aggression will be caused by an incorrect judgement of the aggression of aggressive offenders (and not by an impaired perception). The findings confirmed these hypotheses.