The purpose of the work is to study the possibility of using carbon nanotubes (CNT) as taggants in gun powder to provide expert differentiation of used small firearms cartridges; and to identify the main characteristics of the changes to carbon nanotubes under firing conditions, i.e. short-term exposure to high temperatures and pressures. The principal possibility of using carbon nanotube material for marking gunpowder in small firearms cartridges is stated. There is a need, in both the theory and practice of forensics, to develop such a labeling additive, one that is designed to analyze labeled cartridges and trace their use. We studied the effect of high temperatures and pressures (up to 3000—3500 ºC, 30 MPa) on the behavior of carbon nanotubes by using scanning electron microscopy. We found that the properties of carbon nanotube material — including high chemical and thermal resistance, low prevalence in nature, and a wide variety of forms and configurations — would help solve various investigative issues related to the circumstances of the use of small firearms, in particular, to determine the batch or sample of gunpowder used in the firing of a cartridge.