Findings and methodology are presented for a research project with the following major goals: 1) Use a large sample size of human cadavers from routine death investigations to evaluate the importance and variability of the postmortem human microbiome; and 2) Describe how the microbiome of a living host changes and trans-locates within the body after death.
In achieving these goals, the project describes human epinecrotic bacterial communities (structure) and their functional gene potential on different areas of the body in relation to sex, race, manner of death, geographic location of the body recovery, and autopsy confirmed postmortem intervals (PMIs). The project determined bacterial structure, functional potential, and trans-location (migration or dispersal) within the body during decomposition. The methods outlined and data obtained from this project determined for the first time how commensal bacterial populations in human remains trans-locate and proliferate following death, with robust statistical power. These data may enhance investigations and contribute to crime laboratories by identifying specific microbial taxa or metabolic signatures for potential use in quantifiable, precise measurement of postmortem interval (PMI) used in forensic science. Evidence derived from this process could affect prosecution, exoneration of defendants, and justice for victims. Methods for cadaver swabbing and sample collection have been compiled and disseminated to crime-scene investigators at the Wayne County (Michigan) Medical Examiner's office, and training has been conducted for standardized sample collection. 8 figures and 1 table