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The Smelly Side of Forensics

female scientist viewing sequence on film

The smelly side of forensics

By Stephen Luntz

The bacteria in decomposing bodies can help to determine when a person died – even if only a skeleton remains.

Studying the decomposition of pigs might sound like it’s a promising topic for a rival column called “Uncool Careers”, but add the word “forensics” and Dr Rachel Parkinson belongs on this page.

“Human decomposition is a littleunderstood process, and even less is known about the microbiology involved,” Parkinson says. “My research aimed to investigate the bacterial species that decompose human bodies and determine whether they can tell us when that person died.”

Prime time television has made forensics the hottest area of science among potential students, but Parkinson says funding has not kept pace. Consequently exciting research projects languish for lack of money, and few people have looked into the bacteria that break us down after death. Even Parkinson came to the topic on a tangent.

Parkinson’s Masters degree at Victoria University, Wellington, studied soil bacteria in order to improve forensic matching of soil on shoes. Having achieved some success, one of her colleagues wondered if the research could be put to any other uses, and suggested applying it to decomposition. This became Parkinson’s doctorate.

Since human bodies are not readily available for her studies, Parkinson went to work on pigs. “I got used to the smell and the maggots, but you have to hold your breath a lot,” Parkinson says.

To be sure that her research was significant she needed to know if swine and human decomposition bacteria are similar. To answer this question she contacted the University of Tennessee’s Forensic Anthropology Facility and asked to work on human bodies. “They were really supportive,” she says. “The lead scientist became one of my supervisors, and they told me I’m welcome back any time. They’ve got this great facility there, and its not used as much as it should be.” Parkinson attributes this to the limited opportunities for people to get into forensics anywhere in the world, and the lack of funding for research projects.

For Parkinson, however, the path to forensics was quite easy. “At school I wanted to be a doctor because I didn’t really know what the options were in science,” she says, despite her mother being a hospital laboratory scientist and encouraging her children in science. “At university I discovered microbiology and biochemistry and decided I liked them, so that was my undergraduate degree at the University of Otago.”

Parkinson then moved to Wellington and approached her new department about a research project, saying: “What have you got?” This turned out to be the soil matching studies.

Having completed her doctorate in December 2009, Parkinson is now working in another area of forensics at the Environmental Science & Research Crown Institute. She says that she can’t talk about the work she is doing there because “we have to stay one step ahead of the criminals” She jokes that not all the viewers of CSI are law-abiding, and the people the police are trying to catch are becoming smarter about avoiding detection, although she acknowledges this is more common with minor crimes than murders committed in fits of anger.

Parkinson plans to move to Vancouver, where her partner lives. “I haven’t got a job,” she admits, but notes that Simon Fraser University does a lot of good forensics research. She probably won’t get to take her PhD work any further, but the potential is clear for someone else if funding becomes available.

Parkinson has proved that humans and pigs are broken down by the same combination of bacteria from the body and surrounding environment, making it possible for work to continue in New Zealand. She also demonstrated that the bacteria involved in decomposition change with time, indicating that it should be possible to create a test that will improve the accuracy of estimates of how long a body has been dead.

Intriguingly, Parkinson says this could extend after the body has apparently been reduced to a skeleton. “Bones are still being degraded after everything else is gone,” she says. “Also there are still nutrients in the soil long after you can no longer see chunks of flesh. Once the bacteria that decomposed the body run out of food they die, and then they are eaten by other bacteria.”

Parkinson demonstrated that it is possible to track these changes to 9 months after death, and she might have been able to go further were it not for the limited timeline of a PhD. “This is the period forensic scientists are interested in,” she says. “They already have good techniques for estimating shorter periods after death.”