Evaluation of the similarity of images of breech face marks using the method of correlation cells

The comparison of cartridge cases is required in the course of criminal investigations of cases associated with illegal use of firearms. Lately, have been developed a few methods of forensic investigation of the marks presented on the digital images of discharged cartridge cases. However, it is essential to improve the quality of the comparison of the marks presented on digital images. The aim of the research is development of a more effective method for evaluation of the similarity of marks presented on the primers surface of cartridge cases and produced by the breech face of the weapon. The paper presents a new method of correlation cells. According to the method the investigated images are divided into small cells, the areas with insufficient information are excluded from the comparison. This approach allows to improve the sensitivity of the comparison and to get the additional information about the correlation between the marks on the compared images. On the bases of the calculated likelihood ratio the criteria of matching and not-matching were defined. The presented method is intended to be used for searching similar breech face marks in the database of digital images of the cartridge cases.