This study monitored the transfer of inorganic and organic gunshot residues (IGSR and OGSR) in cases where indirect exposure might be questioned, such as during arrests. Mock arrest scenarios (n = 180) were created to assess the effect of two variables on the secondary transfer. First, the level of contact between the detained and the officer (low, medium, and high) during the arrest protocols. Second, the activities preceding the arrest include situations where the officer or person of interest (POI) discharges a firearm or handles a gun without firing. Additionally, measures to mitigate the risk of GSR transfer from the arresting officer and surfaces were evaluated. This included variables like hand washing, wearing various types of gloves, and bagging the POI's hands during transport in a police vehicle (n = 70). All samples underwent screening (ECD and LIBS) and confirmatory analysis (SEM–EDS and LC–MS/MS). The results indicated that IGSR and OGSR behave differently, with their transfer and persistence varying according to the level of contact, activities, and exposure prior to arrest. Secondary transfer was observed in 69% of the experiments but was less likely to occur for OGSR than for IGSR. The OGSR was more prone to loss, as it was not detected in 93% of the medium- and high-contact scenarios. Preventive measures such as hand washing, wearing nitrile gloves, or bagging hands helped decrease the characteristic IGSR particle counts from 5–80 to none-11. These findings enhance the current knowledge of IGS/OGSR transfer and persistence while providing recommendations for arrest protocols and evidence collection.
(Publisher abstract provided.)