Fighting crime with the microbes

Microbiomes are being studied by researchers at the University of Illinois at Chicago in a completely novel method. They are inquiring as to whether it would be possible to find a criminal using the particular variety of microorganisms that they leave at a crime scene.

Their latest research, "Microbial signatures as trace evidence in residential burglaries," was presented at the American Society for Microbiology's annual meeting, ASM Microbe, which took place in Atlanta, Georgia.

The researcher who presented the results, Jarrad Hampton-Marcell, clarifies:

"Microbial signatures can be used to distinguish one person from another if they are found in a constructed environment, which is the habitat in which humans reside. "In forensic investigations, the microbiome may function as trace evidence," he continues.

Decomposition of deceased biological material is among the most basic processes that occur on Earth. Most matter decomposes into organic plant waste, which is a process that is reasonably well known. However, the ecology of vertebrate decomposition—including human decomposition—is very poorly understood, and forensic science may benefit from a greater understanding of human decomposition.

36 cadavers were dissected as part of this new multi-year study at three distinct forensic anthropological institutions: Colorado Mesa University, Sam Houston State University, and the University of Tennessee, Knoxville. The corpses broke down in all four seasons and in various climates. Next, during the first 21 days of each decomposing body's decomposition, the research team took samples of skin and dirt.

A future in forensics

Forensic science stands to gain significantly by determining the consistent composition and temporal arrangement of the decaying microbiome.

Metcalf and her collaborators, Rob Knight, director of the Center for Microbiome Innovation at the University of California San Diego, and David Carter, professor of forensic sciences at Chaminade University of Honolulu, developed a tool that can accurately predict a body's time since death, also known as the postmortem interval, using machine learning techniques and data from the new study as well as previous work.

"When you're dealing with investigating murder scenes, there are very few types of physical data you can be certain will be present at every scene," Carter said. "You never know if something might contain fingerprints, bloodstains, or video footage. But microbes will always be present."

Carter also mentioned that these bacteria can be particularly beneficial in the kinds of circumstances that the recent study examined. "We're talking about outdoor death scenes," he stated. "It can be difficult to gather information in those types of investigations.