Persistence of inorganic gunshot residue in the hyponychium: Tackling post-shooting hand cleaning challenges

Purpose Gunshot residue (GSR) analysis is a crucial forensic application in the investigation of firearm-related crimes. This analysis traditionally relies on samples collected from the hands of suspected shooters. However, post-shooting activities such as hand cleaning can significantly diminish the presence of GSR on the hands, which compromise the use of routine sampling techniques. This study explores the potential of the hyponychium – a sheltered anatomical region beneath the free edge of fingernail – as an alternative GSR sampling site that may retain particles longer despite post-shooting hand cleaning activities. Methods Using six participants, samples were collected from both hands and the hyponychium following firearm discharge, with GSR particle counts analyzed via scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX). Post-shooting activities including hand wiping with paper towels, wet wipes, rinsing with water, and washing with soap and water were performed to evaluate GSR persistence in the hyponychium. Results Obtained results demonstrated that the dorsum of the right hand initially contained the highest GSR particle count. However, all post-shooting cleaning methods significantly reduced the particle numbers on the hands, with washing with soapy water nearly eliminating detectable GSR. In contrast, the hyponychium consistently retained GSR particles, albeit at reduced levels, even after washing. Conclusion Findings suggested that the hyponychium is a promising supplementary sampling site for GSR analysis, particularly when conventional hand samples are compromised by post-shooting hand cleaning methods. This alternative approach may improve analytical accuracy in cases where critical evidence might otherwise be lost.