Environmental and Post-Mortem Factors Influencing DNA Degradation: Mechanisms, Patterns, and Analytical Implications

Abstract

DNA degradation is a major determinant of the quality, interpretability, and evidentiary value of biological material in forensic genetics, particularly when samples are exposed to adverse environmental or post-mortem conditions. Following death and loss of cellular homeostasis, DNA becomes increasingly susceptible to enzymatic, hydrolytic, oxidative, photochemical, and microbial damage, resulting in progressive strand fragmentation, base modification, and loss of amplifiable genetic targets. This review examines the principal environmental and post-mortem factors governing DNA degradation, with emphasis on temperature, humidity and moisture, ultraviolet radiation, microbial activity, substrate characteristics, post-mortem interval, autolysis, putrefaction, and tissue type. The molecular consequences of these processes are considered in relation to low-template and touch DNA, including allelic dropout, heterozygote imbalance, preferential loss of longer targets, and reduced amplification efficiency. The review further evaluates conventional and contemporary approaches for assessing degraded DNA, including restriction fragment length polymorphism, flow cytometry, comet assay, polymerase chain reaction-based approaches, quantitative PCR, capillary electrophoresis, and next-generation sequencing. Particular attention is given to mini STRs, single nucleotide polymorphisms, and microhaplotypes as strategies for obtaining genetic information from highly fragmented templates. Emerging approaches involving targeted enrichment, artificial intelligence, and advanced sequencing technologies are also discussed in the context of improving the analysis and interpretation of compromised forensic samples. Overall, understanding the mechanisms and patterns of DNA degradation is essential for informed evidence selection, optimized DNA recovery and analysis, appropriate interpretation of partial genetic profiles, and development of robust forensic genetic workflows. Continued advances in sequencing, bioinformatics, and standardized analytical frameworks are expected to enhance the recovery and interpretation of genetic information from environmentally and post-mortem compromised biological evidence.