Metcalf_Mouse_Decomp_Forensics_2011_18S

Establishing the time since death or postmortem interval (PMI) is critical in the initial stages of death investigations, yet existing techniques are susceptible to a range of errors and biases. For example, forensic entomology is widely used to assess PMI, but errors can range on the scale of days, weeks or season depending on the scenario1. Limitations of forensic entomology include uncertainty in the interval between death and initial egg deposition2, lack of insects during particular weather events or seasons3, and regionally specific blowfly larval growth curves and insect communities4. Microbes may provide a novel method for estimating PMI that might avoid many of these limitations, because microbes are ubiquitous in the environment, located on humans before death, and can be reliably quantified using high-throughput DNA sequencing. However, the feasibility of using microbes forensically has yet to be rigorously tested, and we must determine whether microbial community change is sufficiently measurable and directional during decomposition to allow accurate predictions. Here, we show that postmortem microbial community changes are dramatic, measurable, and repeatable in a mouse model system, allowing estimates of PMI to within ~3 days over 48 days, and provide insight into the ecological factors underlying succession of bacteria and microbial eukaryotes within the decomposing corpse system. Our results suggest that microbial community data can be developed into a forensic tool for estimating PMI.