Green forensics: characterization and application of an eco-friendly eggshell-derived small particle reagent for...

Growing global emphasis on environmental sustainability has prompted forensic scientists to explore green and biocompatible methodologies, particularly for latent fingerprint development on challenging surfaces. This study presents an innovative, eco-friendly small-particle reagent (SPR) synthesized from waste chicken eggshells, a biogenic material primarily composed of calcium carbonate, as a sustainable alternative to traditional SPRs, which often contain toxic or heavy-metal-based compounds. The eggshells were processed into a fine powder and characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) to ensure a suitable particle size and composition for forensic use. The formulation was enhanced with natural saponin derived from Sapindus mukorossi as a surfactant and methylene blue as a contrast agent. Eight commonly encountered nonporous substrates including glass, metal, and various plastics, were selected for testing, each bearing sebaceous fingerprints from multiple donors. After immersion in water for 5 days to simulate real forensic scenarios, eggshell-based SPR demonstrated excellent efficacy, producing high ridge clarity and contrast, particularly on glass and metal surfaces. Fingerprint quality was assessed via a standardized grading scale by independent evaluators, which consistently yielded good to excellent results. FESEM-EDX analyses confirmed the strong adherence of the reagent to the fingerprint ridges and that its biogenic composition was dominated by calcium carbonate. A comprehensive ATR-FTIR analysis confirmed the successful deposition and molecular composition of the developed latent fingerprint, identifying characteristic organic residues alongside a dominant calcium carbonate substrate. This approach not only offers a cost-effective, nontoxic, and sustainable alternative to conventional SPRs but also exemplifies the transformation of waste into valuable forensic tools, reducing environmental impact and supporting circular economy principles. The findings pave the way for broader adoption of eco-friendly practices in forensic science, providing law enforcement and forensic professionals with an effective, safe, and environmentally responsible solution for latent fingerprint development, even under water-immersed conditions.