Time Since Death? Ask the Microbes

As many microbiologists can attest, microbiome research is not for the squeamish. From swabbing roadkill carcasses to isolating the DNA present in human waste samples, microbiome researchers aren’t afraid to get dirty – they probably even enjoy it. Yet, it’s hard to imagine that Dr. Nathan H. Lents and his team from John Jay College of Criminal Justice, City University of New York, enjoyed their probing of 21 decomposing cadavers. As part of study published recently in PLOS ONE, Lents and his team collected and analyzed bacteria from the ears and noses of cadavers as the corpses decomposed over the course of weeks.


You may not know that the forensic techniques used currently to identify how long someone has been dead are still not very precise. As such, death investigations, which often include identifying what’s known as the postmortem interval (PMI), or the time that has elapsed since a person has died, provide limited answers to critical questions. That’s what inspired the researchers to analyze the “necrobiome” – the community of microorganisms found on a dead body.


As described in the publication, the research team sampled skin microbiota from the noses and ears of decomposing cadavers to see if they could gain microbiological clues that can eventually be used to help more precisely identify times of death when dead bodies are found. Specifically, the researchers noted the importance of analyzing the cadavers as they decomposed, as it enabled them to take stock of which microorganisms took over the sampled parts of the body, and at what times. They are hopeful that this proof-of-concept study will lead to the realization of reliable microbial indicators that will enable forensics experts to better determine time since death.


It’s also important to note that the team relied on next-generation sequencing and metagenomic analysis of the necrobiome samples to capture the most comprehensive and accurate information for their research. While this study is certainly novel, it joins a growing number of publications that are focused on leveraging metagenomic DNA sequencing and analysis techniques to improve forensic investigations. Bacteria may now often be the culprits, causing deaths through infections, but as this and other studies show, they may soon be helping convict human murderers instead.