Department/unit chief - Forensic Department "Microanalysis", IRCGN
Determining the presence of GSR is a common practice in forensic investigations when firearms are used. The presence of GSR is searched on pieces of evidence coming from the suspect of the shooting (hands, face, clothing) or other support of interest (cars, etc.). At the same time, the interpretation of the results as to the presence and number of GSR is of decisive importance when they are confronted with the hypotheses of investigation and placed in the context of the case.
For this purpose, in the murder case with several shots from a vehicle, a comparative study on different categories of vehicles and a scenario are conducted to assess the indicative value of the GSR found in the suspect's car. Each of the car categories is defined from the statements of the suspect and the scenario is based on investigations (shooting conditions, testimony, ballistic expertise, etc.).
Scanning electron microscopy.
These results allowed to evaluate the strength of the link between the suspect car and the car categories of this study, but also to evaluate the GSR pollution sources linked to activities and statements of the suspect in comparison with the fact circumstances.