News Feature: Can microbes keep time for forensic investigators?

On a small hill outside of Grand Junction, CO, the sun beats ondry earth, and humanbodies lie face up amid low sagebrush. Inside each corpse, on it, and beneath it, a rich ecosystem of bacteria, nematodes, and other microbes flourishes. As these tiny forces of nature—constituents of the postmortem microbiome—steadily decompose the remains, scientists document their every move. At Colorado Mesa University’s Forensic Investigation Research Station (FIRS), researchers are studying these bodies—now up to 11—to learn about the waves of microbes that bloom and fade at each stage of human decomposition. With advances in microbiology and genomics and the declining costs of DNA sequencing, microbes are poised to play a big role in forensics. Researchers have shown that microbes have the potential to alter toxicology results, point to causes of death, and even place a suspect at the scene of a crime (1). If researchers can identify collections of microbes that predictably turn up at specific time points as a body decomposes, then this “microbial clock” could become a powerful tool for crime scene investigators looking to estimate the time and even the circumstances of death. Recent studies suggest that a microbial clock may well exist. But before this forensic tool can be deployed at crime scenes and in courtrooms, researchers first must prove that the clock ticks reliably whether a body falls in lush forest or dry field, whatever the season.