The issue concerning the establishing time limits of sweat and grease traces of the papillary lines has been of concern to forensic scientists for a long time. It is a pressing issue up to this day. This is due to a number of reasons, first and foremost the need:
– to set the time for committing a non-obvious crime;
– the fact of the formation of traces in a specific period of time, which indicates the relationship of these traces to the event of the crime;
– the choice of the optimal method for detecting invisible traces or enhancing the contrast weakly-visible traces, etc.
At the first stage of comprehension the issue it was discussed about specific chemicals and their mixtures for the detection of the sweat and grease substance, which, as a rule, is layered on the subject-trace carrier by papillary lines of a palm surface of the hands or feet. Here it should be taken into account the period of time since the formation of the trace, the temperature of the environment, the morphology of the trace surface, etc. The incorrect definition of the time of trace formation entails the choice of a method that will not be able to reveal invisible traces.
Subsequently, the issue of establishing time limits of the formation of sweat and grease traces of papillary lines has shifted to a different plane. Before experts were posed the issue to establish time limits of traces, based on the mechanism of their formation and detection, by conducting experiments, during which were simulated the processes of trace formation and detection of traces in specified conditions.
The analysis of the methodological provision of expert studies on the establishment of time limits of the formation sweat and grease traces of papillary lines showed its imperfection at the present stage.
In fact, there are two methodological approaches to establishing time limits of traces: using the method of thermo-vacuum spraying (fresh (2-3 days) and ancient (15-day) traces) and the method of lipid analysis using thin-layer chromatography (up to 6 months).
At the same time, these methods were considered without taking into account other types of information that can carry sweat and grease traces of the papillary lines (odorology, dactyloscopic, gene, dermatological, biological and other types of information fields).
It is concluded that it is necessary to update the methodological support for expert studies to establish time limits for the formation of sweat and grease traces of papillary lines, taking into account modern technologies for identifying, fixing and removing such traces, information fields that they (traces) carry in themselves, starting from the actions of the forensic specialist during examination the scene of the incident and ending with the work of the forensic expert in the laboratory during the expertise.