Preserving Evidence: Spectroscopic Fluid Identification

Abstract The definitive identification of biological fluids recovered at crime scenes represents a critical pillar of modern forensic serology and reconstruction. Conventional biochemical screening and immunochromatographic confirmatory assays—such as the Kastle-Meyer, Phadebas, and RSID platforms—remain inherently destructive, analyte-specific, and prone to false-positive or false-negative outcomes when confronted with trace or environmentally compromised stains. Over the past two decades, vibrational spectroscopy, specifically Raman spectroscopy and Attenuated Total Reflection Fourier-Transform Infrared (ATR-FTIR) spectroscopy, has emerged as a transformative, non-destructive analytical paradigm. By interrogating intrinsic molecular vibrations without chemical reagent consumption, both techniques preserve the structural integrity of genomic DNA and trace cellular architecture for downstream Short Tandem Repeat (STR) profiling. This systematic review examines the historical emergence, physical principles, instrumentation, characteristic spectral biomarkers, pre-analytical variables, substrate interference correction algorithms, degradation kinetics, and chemometric deconvolution strategies governing Raman and ATR-FTIR bio-spectroscopy. Furthermore, to bridge the gap between proof-of-concept spectroscopy and routine forensic deployment, this review synthesizes quantitative study characteristics, donor cohort sizes, validation metrics (sensitivity, specificity, AUC, R 2 , RSD, and LOD/LOQ), inter-laboratory model transferability barriers, and courtroom admissibility standards.