# Scanning Electron Microscopy Techniques in the Analysis of Gunshot Residues: A Literature Review
## 4 Discussion
### Interpretation and Reporting of Results  
Criteria for identifying gunshot residues using SEM-EDX are based on both morphological and elemental analysis. SEM-EDX provides detailed information about the shape and size of particles as well as their elemental composition [27; 48; 49; 50; 51; 52; 53]. Morphologically, GSRs exhibit distinct characteristics such as spherical shapes or irregular particles with specific surface textures, which are identifiable under a scanning electron microscope [27; 47; 48; 49]. This dual approach ensures that the identification of GSRs is both accurate and reliable, as it eliminates false positives that may arise from analyzing morphology or elemental composition alone [27; 48; 49; 50; 51; 52; 53]. Interpreting elemental composition data from SEM-EDX analysis involves comparing the detected elements against the known standards for GSRs. The characteristic elements--typically lead, barium, and antimony--are  
Figure 2: Analysis of GSRs using SEM. The process involves collecting samples from the suspect’s hands; analyzing the residue under SEM; and detecting characteristic elements such as lead (Pb), barium (Ba), and iron (Fe) to confirm the presence of GSRs. analyzed quantitatively to confirm their presence and proportions [27; 48; 49; 50; 51; 52; 53]. For instance, photomicrographs from SEM/EDX can reveal the indefinite morphology of GSRs from clean-range ammunition, which contrasts with conventional GSRs [53; 54; 55]. This distinction is crucial for forensic experts who need to differentiate between genuine GSR particles and other environmental contaminants. The interpretation is guided by established forensic protocols that emphasize both the presence of these specific elements and their relative abundances within the sample [48]. Reporting findings from SEM-EDX analysis in forensic investigations involves presenting both the morphological and elemental data in a clear, concise manner. The technique offers visual identification through detailed photomicrographs and spectral data that show the chemical composition of GSR particles [27; 48; 49; 50; 51; 52; 53]. These findings are then compiled into comprehensive reports that include interpretations of the data, potential sources of the residues, and their implications for the investigation. For instance, the presence of significant amounts of GSRs on a suspect can suggest recent discharge of a firearm, thus providing crucial evidence in criminal cases [27; 48; 49; 50; 51; 52; 53]. The specificity and accuracy of SEM-EDX make it a useful tool in forensic science, helping to establish connections between suspects and crime scenes [27; 48; 49; 50; 51; 52; 53]. Notable forensic cases involving SEM and gunshot residue (GSR) analysis underscore the critical role of this technology in criminal investigations. One such case is the landmark investigation of the assassination of President [PERSON], where SEM was crucial in examining GSR particles found on various surfaces and clothing items to reconstruct the sequence of events [27; 48; 49; 50; 51; 52; 53]. These residues, specifically lead (Pb), barium (Ba), and antimony (Sb), were analyzed using SEM coupled with energy-dispersive X-ray spectroscopy (EDS), providing conclusive evidence that linked the firearm discharge to specific locations and individuals [27; 48; 49; 50; 51; 52; 53]. Another significant case involved the analysis of GSRs in a high-profile murder trial, where SEM/EDS technology was instrumental in confirming the presence of primer residues on the suspect's hands, thereby corroborating eyewitness testimony and strengthening the prosecution's case [27; 48; 49; 50; 51]. In the judicial context, we must evaluate various factors including the chain of custody, the precision of the SEM technique, and the expertise of the analyst in determining the admissibility and weight of the evidence.