Chaminade director of forensic sciences and a hui of scientists research PMI
It may sound morbid, but David Carter, Ph.D., wants to figure out how long people have been dead. And he may just be able to do so, thanks to a $830,000 grant from the National Institute of Justice (NIJ). In collaboration with colleagues from Colorado Mesa University, University of Tennessee Knoxville, Northern Michigan University, Western Carolina University, Texas State University San Marcos and University of Québec at Trois-Rivières, the hui of forensic scientists is studying microbial communities with hopes of discovering their own forensics Holy Grail.
“What’s the first question that a loved one asks after a death, ‘When did he or she die?’” Carter asks rhetorically. “There’s definitely increasing interest in PMI (Post-Mortem Interval or the time that has elapsed since an individual’s death). It’s critical information that could be key to solving a crime—or providing an alibi—in absence of any witnesses … or insects.”
The word “forensic” comes from the Latin word “forensis” that means “of or before the forum.” According to the Department of Justice, forensic science is a critical element of the criminal justice system. Forensic scientists examine and analyze evidence from crime scenes and elsewhere to develop objective findings that can assist in the investigation and prosecution of perpetrators of crime or absolve an innocent person from suspicion.
And that’s the point of the NIJ grant, which seeks “to create and validate a microbial-based model to predict PMI across locations in the U.S.” Carter’s and his colleagues’ proposed applied research seeks to improve forensic science for criminal justice purposes by increasing knowledge about a potential new type of physical evidence (microbes), and focuses on developing a tool in which the microbiome present on skin or in nearby soils is used as physical evidence to estimate PMI.
“Jessica Metcalf of Colorado State and Rob Knight of UC San Diego and I initiated this research in 2011,” Carter explains. “So, this recent grant is part of a series of funding that has allowed us to continue our research. It’s a sign of success, but we’re still not quite there.”
In their previous research, investigators utilized skin and soil samples associated with 36 human cadavers collected daily for 21 days from three forensic facilities, which predicts PMI within approximately +/- 3 days over the first 21 days postmortem. As a result, this new research provides useful accuracy for crime scene investigations. In the current proposed research, the first goal is to expand the 36-body PMI microbiome database by collecting similar sample types from an additional 18 human cadavers from two additional facilities, which are in a climate type not yet represented in the PMI database. This additional collection will bring Köppen-Geiger classified climate types (tropical, arid, temperate, continental and polar) in the database to include three of the major U.S. climate types.
“I’ll be traveling to Tennessee in February to lead a training workshop,” Carter says. “I’ll teach participants the proper techniques in collecting samples, which will then be sequenced at a forensic lab for further examination.”
An anthropologist major as an undergraduate at the University of Idaho, Carter didn’t learn about forensics until his senior year. But when he did, the Indiana Jones in him decided to attend Bournemouth University in England to pursue his M.Sc. in Forensic Archaeology, eventually earning a doctorate from James Cook University in Queensland, Australia.
“I’ve always been curious about archeology, history and skeletons,” says Carter, whose interest in the “unknown” started in a movie theatre while watching “Indiana Jones and the Temple of Doom.” “I think of death and decomposition all the time.
“I even discuss it at home with my wife, Charlotte—who’s a Medicolegal Investigator with the City & County of Honolulu’s Department of the Medical Examiner,” Carter continues. “I live in the world of the fringe, but people tell me I look so normal.”