Secondary transfer of organic gunshot residues: Empirical data to assist the evaluation of three scenarios

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.

Surveys of organic gunshot residue prevalence: Comparison between civilian and police populations

“…3) were in the low ng 237 range and very often close to the LOD. Such amounts are in the same range as those observed in 238 persistence and secondary transfer studies [10,40], showing that it might be very difficult to 239 distinguish between firearm discharge and incidental contamination. 240 The data from the questionnaire were investigated to look for a potential explanation for the presence 245 of OGSR compounds.…”

“…In this case, how relevant would be the detection of DPA alone? As 470 highlighted by others [10,18], the simultaneous detection of several compounds has greater value than 471 that of a single compound. This was also confirmed in the present study, as the detection of more than 472 three OGSR compounds together was generally related to a direct or indirect contact with firearms.…”

“…These 369 results imply that it is rare to detect more than one OGSR compound beyond 24 hours without a 370 secondary transfer explanation. Two recent studies highlighted secondary transfer during a handshake 371 or firearm displacement [10,41]. For police officers, manipulation of a firearm involves generally 372 more than ten seconds of contact, as investigated in the first aforementioned study [10].…”

“…Two recent studies highlighted secondary transfer during a handshake 371 or firearm displacement [10,41]. For police officers, manipulation of a firearm involves generally 372 more than ten seconds of contact, as investigated in the first aforementioned study [10]. Depending on 373 the background contamination and the intensity of the manipulation, such as opening the breech or 374 removing the charger, a high degree of secondary transfer might occur as confirmed in the present 375 study and in the second aforementioned study [41].…”

“…Thus, it might be possible to detect GSR on an individual not involved in 53 any firearm discharge. As indicated in the literature, such events are not negligible and should be 54 considered when interpreting GSR traces [6][7][8][9][10]. Therefore, it is essential to estimate the chances of an 55 individual testing positive for GSR without being involved in a firearm incident.…”