[Establishment of mechanisms for the occurrence of blood imprints, taking into account their qualitative and quantitative indicators].

The purpose of the study is to establish the mechanisms for the formation of blood imprints, taking into account morphological features and some quantitative indicators of these blood traces. An analysis of the results of experimental modeling of contact marks (blood prints) resulting from the impact of a gloved hand is presented. The type of impact (shock, pressure) and duration of pressure (short-term pressure 1 - 3 sec, long-term pressure 20 - 120 sec) were determined. Under impact, the main elements of prints are formed regardless of the absorbent properties of trace-forming and trace-receiving objects: a) their contours (edges) are uneven, finely and coarsely serrated; b) the central part of the trace with an uneven thickness of the blood layer; c) second splashes are oval, spindle-shaped, ray-shaped (needle-shaped) and in the form of an exclamation mark; d) medium-speed elements - dynamic blood flows encircling or strip-like (long and narrow, short and wide). The absorbent properties of the trace-receiving material under pressure do not have a significant effect on the formation of the main elements of the traces: a) the contours (edges) of the prints are relatively even; b) the central part of the trace is more pronounced than the peripheral part, which is more clearly visualized on non-absorbent materials; c) low-velocity elements - «dynamic streaks» of blood are strip-like (short and narrow), appear only with sharp pressure, regardless of the exposure of the contact. For traces-imprints from long-term pressure, in contrast to short-term pressure, the following is characteristic: a) the thickness of the trace is on average 1.3-1.6 times greater with a high degree of significant difference in indicators (<0.001); b) more uniform distribution of blood over the imprint area with a high degree of significant difference in indicators (from <0.002 to <0.001); c) clearer and smoother contours with a high degree of significant difference in indicators (<0.002).