Death time can be traced by observing microbe arrival in decomposing bodies

In a study that has the potential to advance forensic science to help investigators probe a case, a team of experts at the Colorado State University decomposed 36 dead bodies for a year while observing the role of insects that are responsible for the arrival of a network of 20 microbes that drive the decomposition process.

In a study that has the potential to advance forensic science to help investigators probe a case, a team of experts at the Colorado State University studied the decomposition of animal flesh that is driven by a network of 20 microbes. Funded by the National Institute of Justice of US, the teams undertook microbial observations in 36 dead bodies or cadavers (corpse meant for dissection) as the research terms it.

All the 36 cadavers were subjected to extensive observations at the University of Tennessee, Knoxville; Sam Houston State University; and Colorado Mesa University— all three being dedicated forensic anthropological facilities.

The research teams left the bodies to decompose under varying climate conditions across four seasons of the year, after which skin and soil samples were collected for each decomposing corpse. "It’s really cool that there are these microbes that always show up to decompose animal remains," said Jessica Metcalf who is the senior author of the study.

The researchers gathered a significant amount of molecular and genomic details from the samples, and regardless of the climatic situation, they found a same set of around 20 "specialist decomposing microbes" on all 36 cadavers. Genomic and molecule movements served to be the ladder for the scientists for understanding the play of "microbial community" in a decomposing or decomposed body.

They observed that the insects played a crucial part in the arrival of microbes. The microbes arrived onto the decomposing bodies "like clockwork at certain points throughout the 21-day observation period". According to Metcalf, “We see similar microbes arrive at similar times during decomposition, regardless of any number of outdoor variables you can think of.”

Moving further, Metcalf collaborated with David Carter who is a professor of forensic sciences at Chaminade University of Honolulu, and Rob Knight, director of the Center for Microbiome Innovation at the University of California San Diego. The collaboration built a tool that can accurately predict a body’s time since death, also known as the postmortem interval.

According to Carter, “When you’re talking about investigating death scenes, there are very few types of physical evidence you can guarantee will be present at every scene, You never know if there will be fingerprints, or bloodstains or camera footage. But the microbes will always be there.”

Nancy La Vigne, the director of the National Institute of Justice said, “One of the principal questions of any death investigation is when did this person die? This continuing line of NIJ-funded research is showing promising results for predicting time of death of human remains, aiding in identification of the decedent, determining potential suspects and confirmation or refutation of alibis.”