Forensic Implications of Organic Gunshot Residue (OGSR) Degradation in Delayed Evidence Collection Scenarios: an Assessment of Environmental Stressors on OGSR Stability Using Raman Spectroscopy

Gunshot residue (GSR) is a key form of trace evidence in firearm-related investigations It comprises of two main components namely inorganic GSR (IGSR) and organic GSR (OGSR). IGSR is traditionally classified based on particle morphology and elemental composition. However, this approach becomes challenging for residues from non-traditional ammunition, including heavy metal-free primers. Consequently, there is increasing interest in incorporating OGSR into forensic protocols and developing standardized approaches for its interpretation. As indicated in several studies, OGSR detection can be affected by environmental variables; however, a systematic study on its stability under defined temperature and humidity conditions remains limited. In this study, we evaluated the chemical stability of OGSR under controlled laboratory simulations of temperature and relative humidity. The conditions were selected to represent ambient scenarios relevant to typical Indian weather, with temperatures ranging from 10 to 60 degrees C, relative humidity from 45% to 95% RH and exposure time varying between 0 and 8 h. A total of 51 OGSR samples were collected under controlled indoor firing-range conditions using 9 & times; 19 mm ammunition. These samples were subjected to artificial ageing in environmental chambers and exposed for different durations within this time window to study the degradation pathway of OGSR. To interrogate these potential degradation pathways, OGSR stability was monitored using Raman spectroscopy to detect time-dependent vibrational spectral changes. The results demonstrate no measurable changes in OGSR profiles under the tested temperature-humidity-exposure time combinations and, highlighting factors that influence OGSR detectability when evidence collection is delayed within hours after discharge. These findings provide condition-specific data to support interpretation of OGSR in forensic casework, while noting that longer-term persistence and complex outdoor scene effects were not evaluated in the present study.