Characterization of volatile organic gunshot residues in fired handgun cartridges by headspace sorptive extraction

Abstract

In forensic investigation of firearm-related cases, determination of the residual amount of volatile compounds remaining inside a cartridge could be useful in estimating the time since its discharge. Published approaches are based on following the decrease of selected target compounds as a function of time by using solid phase micro-extraction (SPME). Naphthalene as well as an unidentified decomposition product of nitrocellulose (referred to as "TEA2") are usually employed for this purpose. However, reliability can be brought into question given their high volatility and low reproducibility of the extracted procedure. In order to identify alternatives and therefore develop improved dating methods, an extensive study on the composition and variability of volatile residues in nine different types of cartridges was carried out. Analysis was performed using headspace sorptive extraction (HSSE), which is a more exhaustive technique compared to SPME. One hundred sixty six compounds were identified (several of which for the first time), and it was observed that the final compositional characteristics of each residue were strongly dependent on its source. Variability of single identified compounds within and between different types of cartridge as well as their evolution over time were also studied. Many explosion products containing up to four aromatic rings were found to be globally present in high proportions. Twenty-seven of them (excluding naphthalene) also presented detectable decreases during the first 24 h. Therefore, they could be used as complementary target analytes in future dating methods.

A study of transfer and prevalence of organic gunshot residues

“…This could include linking a person to such an event, an estimation of shooting distance and trajectory, bullet entry and exit point identification or simply determining the circumstances of a case and verifying the veracity of a testimony [1][2][3]. Additional information concerning the type of firearm and ammunition used as well as the time since discharge can also be useful [4][5][6][7]. GSR consists of a complex mixture of organic and inorganic material originating from the firearm, the ammunition and the combustion products formed during the discharge [8,9].…”

Time since discharge of 9 mm cartridges by headspace analysis, part 2: Ageing study and estimation of the time since discharge using multivariate regression

“…The same storage conditions as those experienced by the questioned cartridges should be applied to reference material. The type of cartridges used as reference material should also be consistent, as previous research showed a dependence between GSR composition and ammunition [14]. Secondly, that knowledge about the environmental conditions at the crime scene before the questioned cartridges have been sampled should ideally be collected in order to correctly reproduce them in laboratory.…”

“…Out of the 29 substances targeted with the developed method, 21 were chosen as predictors for training (Table S1). The three unaltered smokeless powder compounds (i.e., ethylcentralite, dibutyl phthalate and diphenylamine) were discarded because of low repeatability in their detected amounts [14]. Moreover, five explosion products (i.e., o-and m-tolunitrile, 1,3-and 1,4-dicyanobenzene, and isoquinoline) were also discarded due to co-elution issues compromising their detection and relative quantification (see part 1).…”

“…The latter are partly composed by volatile organic compounds (such as benzonitrile, naphthalene, and pyrene), which condense on the cartridge walls and disappear over time through evaporation and diffusion phenomena [14]. Solid phase micro-extraction (SPME) coupled to gas chromatography was previously proposed as a sampling method to analyse these residual products, while naphthalene and an unidentified decomposition product of nitrocellulose (referred as "TEA2") were suggested as main target analytes [4][5][6][7].…”

The analysis of organic and inorganic gunshot residue from a single sample

“…propellant powder) and combustion products [1]. There are over a hundred organic compounds with a possible association to GSR [1,2], many of which can be found in environmental and occupational materials [1,3]. A small selection of around twenty of these compounds have recently been highlighted as OGSR compounds that have a potential relevance to the confirmation of GSR materials [4].…”