Understanding the dynamics of DNA methylation (DNAm) post-mortem could support forensic applications, particularly the estimation of the post-mortem interval (PMI), age, and sex of remains. In this study, we investigated DNAm changes in pig carcasses (Sus scrofa) as analogs for human decomposition, while measuring the progression of decay. Genome-wide methylation arrays and ELISA assays were run on pig soft tissues collected post-mortem, alongside assessments of DNA integrity. Overall, DNA integrity and DNAm levels declined throughout the post-mortem period, with distinct seasonal differences. We established thresholds for estimating age and sex, referred to as epigenomic profiling, showing that key epigenetic markers retain predictive value post-mortem. Additionally, CpG sites that mapped to the Sus scrofa genome were selected to develop an ElasticNet model that integrated DNAm to estimate the PMI, highlighting the potential of DNAm as an investigative tool. In conclusion, this study is the first to demonstrate the utility of DNAm and epigenomic profiling in extended PMIs, and the first successful attempt to estimate both age and sex post-mortem from DNAm alone.
Badell et al. (Sun,) studied this question.