firing pin traces

Influence of Inhomogeneities of the Surface of Caps on Variability of Static Firing Pin Traces

Introduction. One of the reasons for the variability of the firing pin traces is the gross inhomogeneity present on the surface of the capsules. The main types of not uniformity characteristic of a cap surface, and also their display in static traces are quickly investigated in this work. Experimental part. The surfaces of capsules of various cartridges of domestic and foreign production, as well as capsules “Zhevello” for hunting cartridges, were examined. The main types of inhomogeneities of the capsule surface are analyzed and classified. During the research it was shown that some roughness of the capsule surface does not smooth out when the striker firing pins and can introduce distortions into the static firing pin traces. Conclusions. The carried out researches have shown that the mismatched strongly pronounced features in pair traces can be explained by the presence of similar inhomogeneities on the surface of the capsule outside of the firing pin trace. This fact should be taken into account when comparing static traces of strikers. The work is of interest to firearm examiner specializing in the identification of weapons.

The Comparison of Digital Images of Firing Pin with a Dominant Features in the Form of Circles and Arcs

Introduction. Development of the algorithms for the automatic comparison of the digital images of firing pin is an important task of the forensic examination. This task is aimed at improving the efficiency of crime investigation involving the use of firearms. In this paper images of firing pin with the features in the form of circles and arcs with single center are investigated. The method based on modified Euclidean distance between circles of the similar firing pin was proposed to assess the degree of similarity of the traces. Preliminary processing. To eliminate the adverse effect of noise and various image artifacts were pretreated. Markers were placed to accurately determine the features in the form of circles. Method of searching paired tracks. Criteria based on modified Euclidean distance were developed for the formation of the priority list. Numerical experiment. In the numerical experiment database of 60 objects was used. Paired trace from firing pin array was included in top four of the prior list in 90 percent cases. Conclusions. The proposed algorithm allows to sort effectively and quickly the array of test objects by the degree of similarity of signs in the form of arcs and circles with relevant features of the test track.

Problems of Ensuring Compliance of Technical Characteristics of Civil and Office Firearms to Criminalistic Requirements of the Ministry of Internal Affairs of Russia

Introduction. Problematic issues of providing the criminalistic requirements of the Ministry of Internal Affairs of Russia imposed to firearms are considered in work. A sometimes weapons does not provide formation on the shot bullets and cartridge cases of the traces suitable for identification. Absence of any standards or specifications on a roughness of a relief of surfaces of the details forming traces is to it the reason. In addition, arms manufacturers poorly represent modern methods and technical means of identification of the weapon. Experimental part. In work the reasons of formation of traces on the shot bullets and shot cartridge cases not suitable for identification of the weapon are analyzed. Cases where the identification of the weapons on the striker traces is impossible due to the design of shells hunting cartridges are shown in the article. The negative influence of the production of primers traces at identifying of weapons on firing pin traces is quickly studied. Conclusion. Forensic requirements for identification of the weapon can be most effectively provided at close scientific and technical cooperation of the arms manufacturers and scientists specializing in area of judicial identification of the weapon.