A New Method of Point Clouds Processing for Forensic Comparison of Cartridge Cases

For the more than 100 years forensic firearm identification has been conducted by examining physical evidence under the optical comparison microscope. Nowadays, 3D technology offers advanced and powerful tools that deserve to be considered to evaluate a new and different solution for processing ballistic data. The method proposed in this work is based on the processing of the 3D point clouds of the cartridge case back. It starts with the transformation of the point clouds of the bottom of the cartridge case into a 64-bit greyscale image. The second step is to use a polar derivation technique for exploiting the polar characteristics of the features impressed on the cartridge and also to overcome the problem of the initial orientation of the cartridge. The dataset used for the experimental part was made by Messina Carabinieri Scientific Investigation Department (Italy) and it contains point clouds of several cartridge cases acquired with an Automated Ballistic Identification System (ABIS). After the pre-processing, the method has been tested with SIFT to verify the invariance on the feature extracted. Although not yet ready for forensic applications, the method appears to be promising and innovative to be applied in the common pattern recognition process in this field.