Firearm Classification based on Extensive Jaccard Index of 3D Cross-sectioned Shape of Firing Pin Impression on Fired Cartridge Cases

Abstract

A classification technique of using a new feature named ‘Extended Jaccard index” of cross-sectional shapes of firing pin impression is proposed. The three-dimensional data of the marks on the cartridge cases are measured by a confocal microscopy. After measurement of marks, horizontal and vertical cross-sectional shapes of firing pin impression are effectively extracted. A similarity between the two cartridge cases is designed on these shapes, and the similarities are divided into the identical firearm group and the different firearm group by the quadratic discriminant analysis. As a result, the new feature-based cross-sectional shape evaluation is effective in firearm classification.