The increasing number of homemade sub-machine guns in caliber 9 mm Parabellum received for examination, as well as cartridge cases discharged from this weapon, made it necessary to single out the marks which can be used for group identification. The article gives the results of generalizing and systematization of marks observed during the examinations made in the laboratory. This work singles out the marks and traces which can be observed on the cartridge case surface and can be used for the identification of the type and model of the firearm. The construction features of homemade sub-machine guns were investigated. Among these features are the construction based on open bolt mechanical scheme, the use of static firing pin, methods of barrel assembling and fixing into the body of the weapon, which can lead to the appearance of a hole in the chamber, etc. The article also shows the influence of the tool processing on leaving special marks and traces on the breach face. These marks can also be used for the group identification.
Based on the results of the research the article distinguishes between the main signs, which can be used for group identification, the sings similar to the ones known in factory-made weapons and the signs typical of homemade firearms.
The first group consists of the marks of ejector and the extractor cutouts and the firing pin mark. For these sings the article describes special characteristics which makes it possible to distinguish them from the marks commonly observed on the factory-made examples.
To the marks typical of homemade sub-machine guns can be applied breach face marks, cartridge case deformation, caused by differences between the sizes of the chamber and the cartridge, cartridge deformation while shooting when the cartridge case is not supported by the chamber, perforation of the sidewall of the cartridge case, etc.
The article also discusses the issue of cartridge case comparison and individual identification. Great variety of the traces and marks as a result of low-quality tool processing was revealed. This can be the factor which makes comparison more difficult. However, the big number of individual marks observed on the cartridge cases makes it possible to come to well-grounded conclusion.
Key words: cartridge cases, submachine guns, type and kind of weapon, expert practice.