Forensic Postmortem Interval Estimation from Skeletal Muscle Tissue: A Lipidomics Approach

Lipidomic analyses of human skeletal muscle tissue were conducted to detect biomarkers of time-dependent postmortem degradation and to test the predictive capacity of lipids in human skeletal muscle cell membranes. High-resolution mass spectrometry analytical platforms were used to isolate phospholipids in muscle cell membranes that are specific to the corpse tissues and not invading microbes, thus eliminating potential noise from the surrounding microenvironment. The most consistently extracted cell membrane phospholipids were phosphatidylglycerol (PG) 34:0 and phosphatidylethanolamine (PtdE) 36:4. The actual accumulated degree days of all validation samples fell within the 95% prediction interval limits for the simple linear regression models with PtdE 36:4 and PG 34:0, though the prediction intervals for the latter were wider. The analysis requires only a small amount of tissue, is less subjective than visual methods for estimating postmortem interval, and is robust to drastic fluctuations in temperature. Sophisticated quantitative methods for estimating PMI from biomolecules unique to the corpse, and the human microbiome may provide a means of overcoming the geographic limitations of methods based on subjective visual observations of decomposition changes.