Microbes Could Help Establish Time of Death

A final technical report (the result of an NIJ-funded project but not published by the U.S. Department of Justice) recently released takes a look at utilizing bacterial and microbial eukaryotic communities to establish the time of death.

From the abstract of Characterization of Bacterial and Microbial Eukaryotic Communities (including Fungal) Associated with Corpse Decomposition Using Next Generation Sequencing, written by Jessica L. Metcalf, David O. Carter, and Rob Knight:

 
Establishing the time since death is critical in every investigation, yet existing techniques are susceptible to a range of errors and biases. Forensic entomology, for example, is widely used to assess postmortem interval (PMI), but errors in estimates can range from days to months.
 
This study’s goal was to determine whether the succession of bacterial and microbial eukaryotic communities associated with corpses and their gravesoil are sufficiently predictable to be useful for forensic science and criminal justice. The research focused on two major goals of forensic science: to estimate the PMI of corpses and to locate clandestine gravesites.
 
Using the cadavers of mice, pigs, and humans, as well as their gravesoils in both controlled and outdoor settings, the study found a predictable succession of bacterial and fungal communities associated with corpse decomposition that could be a useful tool for estimating the PMI. In addition, if distinctive communities form in the soil, these could potentially be used to identify clandestine gravesites.
 
While promising, basic research characterizing the dynamics of bacterial and fungal communities associated with corpse decomposition is a critical first step towards establishing whether these dynamics are sufficiently predictable to be useful in forensic science. These future studies are crucial, as previous forensic investigations using traditional indicators have shown that environmental parameters such as temperature, moisture, soil type, and soil texture can affect the rate at which decomposition occurs and the ability of decomposer organisms to function.
 
 
Source: NIJ
 
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