Gunshot residue determination by means of gunpowder stabilizers using high-performance liquid chromatography with electrochemical detection and analysis of metallic residues by graphite furnace atomic absorption spectrophotometry

Gunshot residue detection technologies—a review

Background

Gunshot residue (GSR) is a shred of important trace evidence which helps forensic scientists solve a huge range of incidents related to firearms. The identification of the shooter to bullet identification from a gunshot wound help reconstruct a scene of the crime.

Main body

The review of this scientific paper is based on gunshot residue, its composition, and the growing advanced technology which allow us to study about how GSR analysis help to identify and detect residues. Various methods are acquired to identify and analyze organic and inorganic residues present when ammunition is fired. The review highlights the composition of GSR, its collection methods, and analysis part which emphasize on all the methods developed so far. The use of conventional methods including colorimetric and instrumentation-based analysis and advanced technology including electrochemical technique for detecting residues from the last 50 years. Spot tests or chemical tests were performed but they degrade the sample and can sometimes cause hindrance with some other nearby material present at the crime scene. Instrumentation techniques including AAS, ICP-MS, SEM, SEM-EDX, GC, HPLC, etc. are discussed in detail. Mostly advanced electrochemical methods developed are for inorganic gunshot residues (IGSR), but some researchers worked on both residues. Also, the fabricated electrochemical cells are replaced by a single strip-based technique for easy detection. So, to combat these issues, various scientists are moving towards sensor-based methods for rapid and reliable detection. These methods are more user-friendly, sensitive, and cost-effective and provide rapid detection results.

Conclusions

This review results in the composition of GSR, its collection methods, and analysis using sophisticated methods that emphasize all the methods developed so far and it also culminates the merits and demerits of all detection methods.

Development and application of a new nose hairs sample collection device for GSR Particles by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS)

When a firearm is discharged, a gaseous cloud containing characteristic particles of gunshot residue (GSR) are released forward and behind at high speed, depositing on clothing, hands, face and hair, as well as being inhaled and therefore retained in the nostrils of the person who fired the weapon. GSRs have characteristic sizes and morphologies and consist of a combination of lead, antimony and barium, as well as other elements. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) is a widely accepted technique for the analysis of these residues; however, little has been reported on samples taken from the nostrils of the suspect that discharged the shot. The analysis of residues found on hands has been more frequent. This article presents a device (Nasal Stub) developed by us for the non-invasive collection of GSR particles from the nostrils and a platform also developed by us to contain these devices that is compatible with SEM-EDS. To evaluate the effectiveness of our Nasal Stub to collect GSR particles from nose hairs, four types of firearms of different calibers were utilized. Nasal samples were collected at 0, 2, 4, 6, 8, and 20h after firing. The results show that the nasal device was able to recover GSR particles from nose hairs for all the weapons used, even, in some cases, over 20h after firing. It was concluded that Nasal Stub and its methodology proposed for the analysis of nasal GSR from nose hairs by SEM-EDS was effective and that it can complement other traditional analyses of GSR particles, increasing the amount of evidentiary support for the forensic analysis presented in a tribunal or court.

Analysis of gunshot residues as trace in nasal mucus by GFAAS

When a gun is fired, the majority of gunshot residues are deposited on the shooter's hands. But these residues disappear through contact with surfaces or washing. Therefore, the maximum time frame to find GSR on a suspect's hands is 8h. The mucus, inside of a nostril, forms a surface layer where they are trapped foreign particles. In this way, mucus inside of a gunshot suspect's nostrils could act like an adhesive medium to stick on it gaseous particles from a gunshot. In this study, the presence of GSR in nasal mucus and its residence time is examined. A new procedure for the sampling of possible gunshot residue accumulated in the nasal mucus is designed. Samples are taken with cotton swabs moistened with a solution of EDTA and, after an acid digestion, are analysed by graphite furnace atomic absorption spectrometry. In addition, samples of hands are taken for comparison purposes. GSR recovery has been successful. The concentration of GSR in nasal mucus is found to be lower than on the hands, but with a longer residence time. Thus, it is possible to expand the sampling time of a suspect also, as nasal mucus cannot be contaminated by handling weapons.