Human Environmental DNA: A New Frontier in Forensic Biology

Abstract

Environmental DNA (eDNA) refers to genetic material recovered from environmental matrices without requiring direct collection of an intact biological specimen. In forensic science, human eDNA may originate from shed epithelial cells, hair-associated material, saliva-containing droplets, blood, urine, and other cellular material deposited into air, dust, soil, water, and surfaces. This review examines the forensic potential of human eDNA with emphasis on environmental sources, sampling, extraction, molecular analysis, transfer and persistence, contamination, mixture interpretation, validation and Indian forensic implementation. Unlike conventional biological evidence, environmental DNA may be low-template, degraded, heterogeneous, and affected by primary or secondary transfer. Therefore, detection of a DNA profile should not by itself be interpreted as proof of the timing, mechanism or activity associated with deposition. The review identifies the need for matrix-specific sampling protocols, validated analytical workflows, quality assurance, chain of custody, inter-laboratory studies and scientifically supported interpretation. Current and emerging approaches including STR profiling, massively parallel sequencing, digital PCR, metagenomics, portable sequencing and computational analysis may expand forensic applications, but require appropriate validation before routine casework use. Human eDNA is best considered a complementary source of forensic information while its analytical and interpretive foundations continue to develop.