A chronological study of gunshot residue (GSR) detection techniques: a narrative review

The investigation and reconstruction of firearm-related crimes for the determination of the shooting distance, time since fire, and gunshot residue (GSR) persistence using the analysis of GSR comprising organic and inorganic components are crucial. However, the conventional color tests and allied techniques for GSR analysis are destructive and have limited sensitivity and selectivity. The review gives an elaborate and chronological description of all the methods used to date along with the future aspects of GSR detection techniques. It highlights the significant methods of spectrometry and spectroscopy applied as analytical techniques for the evaluation of GSR. The study is divided into various sections, ranging from the conventional color tests to the current techniques used in GSR analysis. While there is inconsistency and unreliability in these techniques, the current approaches discussed in this study using laser induced breakdown spectroscopy (LIBS), surface enhanced Raman scattering (SERS), ion mobility spectrometry (IMS), and electrochemical sensor-based methods have significant potential for GSR detection. Addressing such limitations will enhance the forensic capabilities of law enforcement and provide an added advantage to forensic laboratories during an investigation. It will also reinforce the use of such spectroscopic data in a criminal investigation. The techniques discussed here have the capability to detect both organic and inorganic components of GSR that has the potential to link GSR particles to the type of ammunition discharged. The validity and reliability of these approaches have proved to establish their capability to differentiate between potential false positives known for standard forensic analysis techniques currently used for GSR detection and identification. The paper anticipates a systematic study of the novel methodologies relevant to the current scope of research concerning GSR analysis, when fully developed and implemented in practice will help forensic scientists to detect, identify, and analyze GSR, making it a new and important type of evidence.