'Microbial Clock' May Help Investigators Determine Time of Death

Determining what time a person died can be crucial for police investigations. Yet it can sometimes be difficult when a body begins to decompose. Now, though, researchers may have developed a new way to tell the time of death of a person--by examining bacteria.

When a person dies, their body becomes a veritable farm for bacteria. The corpse progresses through several forensically recognized stages of decomposition, including Fresh, Active Decay and Advanced Decay. The biotic signatures associated with these stages of decomposition all have certain signatures that allow researchers to better determine the time of death. Yet it's only now that scientists have started looking at microbes.

Microbes are ubiquitous in the environment and play an important role in decomposition. In fact, scientists have now found microbial signatures left of computer keys and computer mice can actually tell them a bit more about victims.

"This study establishes that a body's collection of microbial genomes provides a store of information about its history," said Rob Knight, an associate professor of chemistry and biochemistry at Sam Houston State University, in a news release. "Future studies will let us understand how much of this information, both about events before death--like diet, lifestyle and travel--and after death can be recovered."

Although establishing type of death is crucial for investigations, existing techniques often are susceptible to a range of errors and biases. For example, forensic entomology is widely used to determine time of death; however, this method has errors that can range from days to weeks. By using microbes, though, many of these limitations can be avoided.

"There is no single forensic tool that is useful in all scenarios, as they have some degree of uncertainty," said Jessica Metcalf, one of the researchers, in a news release. "But given our results and our experience with microbiomes, there is reason to believe we can get past some of this uncertainty and look toward this technique and a complementary method to better estimate the time of death in humans."

The new findings could help investigators conducting investigations on dead bodies. It gives them a novel tool to use, which will only yield more accurate results in the future.

The findings are published in the journal eLife.