Fresh vs. frozen human decomposition-A preliminary investigation of lipid degradation products as biomarkers of post-mortem interval

Traditionally, the post-mortem interval (PMI) is determined using methods such as forensic entomology or forensic pathology, however, these techniques are often limited to a particular post-mortem window of up to 72 - 120 h after death. In this study, lipids extracted from decomposing human tissue were investigated as potential soft-tissue biomarkers of PMI. Tissue samples were collected from two whole human donors (n = 2), one frozen and one fresh, placed at the Australian Facility for Taphonomic Experimental Research (AFTER) over the course of 69 days post-placement. These samples were analysed using gas chromatography coupled with tandem mass spectrometry (GC-MS/MS), demonstrating statistically significant differences for most fatty acid analytes and further highlighting the well-known stability of sterol compounds over time. Differences were observed between the fresh and frozen donor, with the fresh donor displaying more distinct stages of decomposition. Chemical differences between the donors were more distinct in the fatty acids than the sterols. The fatty acid profiles over time were further investigated and target analytes comprising saturated fatty acids (stearic acid and palmitic acid) and unsaturated fatty acids (oleic acid and linoleic acid) were found to be of particular importance due to their potential as indicators of PMI.