Light it up! Photoluminescent Lead Detection for Forensic Investigations

Gunshot residue (GSR) analysis is essential for the forensic investigation of shooting incidents, but it is oftentimes slow, cumbersome, and limited in spatial resolution. Here, a photoluminescent GSR analysis (PL-Pb) method is introduced for instant, spatially resolved detection of GSR with high resolution. Lead dust in GSR reacts into a lead halide perovskite semiconductor that emits bright green light under ultraviolet irradiation. The sensitivity of PL-Pb enables straightforward detection of trace amounts of GSR from ricochet markings, bullet holes, and combustion plumes. GSR is to be transferable with high spatial resolution and preserves fine details such as the polygonal patterns caused by rifling in a pistol. Moreover, PL-Pb detection yields reproducible GSR patterns for shooting distance reconstruction series. The sensitivity and instant results make PL-Pb suitable for rapid, onsite testing of shooting suspects. Surprisingly, GSR can still be detected on the hands of shooters after washing, and is easily found on clothes, shoes, and other objects relevant to a shooting incident. Collectively, the instant results and sensitivity of PL-Pb open unprecedented opportunities for on-site forensic investigations and highlight the potential of perovskite-based lead detection methods for lead-containing, crime-related micro-traces and lead dust in general. PL-Pb detection can have a significant advancement in forensic science. It may streamline the process of GSR detection while enhancing the accuracy and reliability of the results. By emitting bright green light upon UV irradiation, a visually striking and easily identifiable marker for lead residues is possible. This may make it invaluable for forensic investigators working at crime scenes, offering immediate and clear results that can be crucial in time-sensitive situations. The ability to detect GSR even after attempts to wash it off further underscores the robustness, reliability, and sensitivity of this method.