Salivary biomarkers in forensic science: Bridging molecular biology and legal medicine

Saliva has emerged as a versatile and non-invasive biological specimen in forensic science. It is a rich source of genomic, transcriptomic, proteomic, metabolic, and microbiomic factors, offering significant potential in forensic investigations. This review explores the multi-dimensional aspects of salivary biomarkers in forensic science, integrating molecular biology with legal medicine. It provides a comprehensive overview of the saliva composition, highlighting its biochemical constituents and the methodologies employed for its effective collection in forensic scenarios. From a molecular and analytical perspective, we delve into the diverse classes of salivary biomarkers, including genomic markers that enable individual and kinship profiling; transcriptomic and proteomic biomarkers that reveal gene expression and protein profiles that contribute in post-mortem interval estimation and physiological state evaluation; and metabolomic and microbiomic signatures which offer additional discriminatory power to infer health, lifestyle, and even geographic origins. The forensic applications of these biomarkers and their growing acceptance in judicial proceedings, where the admissibility and evidential value of saliva-derived data are critically assessed, are discussed. Supported by relevant case studies, this review highlights the real-world utility and impact of salivary biomarkers in forensic practice. The challenges and limitations of saliva in forensics are addressed. Additionally, insights into future prospects, such as salivaomics, lab-on-a-chip platforms, and AI-driven data interpretation, are provided. In conclusion, by mapping the intersection of molecular diagnostics and legal frameworks, this review underscores that saliva can be a revolutionary medium that advances the accuracy and accessibility of forensic identification by bridging its biological complexity with forensic applications.