No abstract

The present study aimed at providing data to assess the secondary transfer of organic gunshot residues (OGSR). Three scenarios were evaluated in controlled conditions, namely displacing a firearm from point A to point B, a simple handshake and an arrest involving handcuffing on the ground. Specimens were collected from the firearm, the hands of the shooter and the non-shooter undergoing the secondary transfer in order to compare the amounts detected. Secondary transfer was observed for the three scenarios, but to a different extent. It was found that displacing a firearm resulted in secondary transfer in less than 50% of the experiments. The firearm also had an influence, as contrary to the pistol, no secondary OGSR were detected using the revolver. Shaking the hand of the shooter also transferred OGSR to the non-shooter's hand. In that case, the amount of OGSR was generally higher on the shooter than on the non-shooter. Finally, the largest secondary transfer was observed after the arrest with handcuffing with positive results in all cases using the pistol. In that scenario, the amounts on the shooter and the non-shooter were in the same range. This study highlights that the secondary transfer must be taken into account in the interpretation of OGSR. Indeed, an individual's hands might be contaminated by handling a firearm or having physical contact with a shooter.

Gunshot residue (GSR) analysis and their interpretation provide crucial information on a criminal investigation involving the use of firearms. To date, several approaches have been proposed for the implementation of a combined sampling and analysis of inorganic (IGSR) and organic GSR (OGSR). However, it is not clear at this stage if concurrent analyses of both types of residue might be detrimental to the analysis of IGSR currently applied in forensic laboratories. Thus, this work aims to compare and evaluate three different protocols for the combined collection and analysis of IGSR and OGSR. These methods, respectively, involve the use of a modified stub (with two halves, one for the detection of IGSR and the other for the analysis of OGSR); the sequential recovery of GSR with two stubs mounted with different adhesives (double‐sided carbon tape and Tesa® TACK) and the sequential analysis of IGSR and OGSR from a single carbon stub following carbon deposition. The detection of IGSR was carried out using SEM‐EDX, while OGSR analysis was performed using ultra‐high‐performance liquid chromatography–tandem mass spectrometry (UHPLC‐MS/MS). Obtained results for experiments performed using Geco Sinoxid® ammunition indicated that sequential analysis was the most suitable protocol for the combined collection and analysis of both IGSR and OGSR. A higher number of inorganic (characteristic and consistent) particles and higher concentrations of ethylcentralite, N‐nitrosodiphenylamine, diphenylamine, and nitroglycerin were recovered with this method.

13This study investigated the prevalence of eight OGSR compounds in a civilian and a police 14 population. Specimens were collected from the hands and sleeves of 122 civilians and 115 individuals 15 working in police services using carbon stubs. Data was acquired using liquid chromatography 16 coupled to tandem mass spectrometry. 17Results indicated a non-negligible prevalence in the civilian sample, with 18% of the 122 civilians 18 sampled having one or more OGSR related compounds on their hands and 11.5% on their wrists or 19 sleeves. For the police population, the prevalence was logically higher than for civilians, with 36.5% 20 of the hand specimens and 33% of the wrist specimens positive for one or more compounds. A higher 21 prevalence was expected for the second population due to the possession of service weapons regularly 22 used during shooting exercises. These results demonstrate that the presence of one OGSR compound 23 is not a rare occurrence, even in a civilian population. Considering the results of this research together 24 with information on alternative sources of the targeted OGSR compounds can serve as a basis for 25 OGSR interpretation in casework. 26 27