Dead men do tell tales, in the form of scents that investigators follow to help discover hidden graves.
Now scientists have isolated 30 compounds specifically linked with buried corpses. The researchers say their findings could help improve training of dogs to unearth concealed bodies and possibly lead to electronic noses that sniff out human remains.
One goal in these corpse hunts: speed.
"The faster you can find graves, the more evidence you can recover," explained researcher Arpad Vass, a forensic anthropologist and research chemist at Oak Ridge National Laboratory in Tennessee.
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At any given time, some 30 buried corpses are in various states of decay at the roughly three-acre Anthropological Research Facility at the University of Tennessee in Knoxville. For the last four years, Vass and his colleagues have taken up the inarguably unpleasant task of investigating the odors given off by the bodies. The dead either volunteered to donate their remains to science or were donated by next of kin.
Perforated pipes above a grave and in the soil above and below the body collect gases for later analysis in the lab. As buried corpses decompose, they release some 478 different compounds over time.
"It's not a pleasant smell," Vass said. "You never get used to it."
It takes about 17 days for odors to first be detectable on the surface, in a case where a corpse is buried about 18 inches deep. "The average clandestine grave is about 2 to 2-1/2 feet deep, according to statistics from the FBI," Vass explained.
In the ongoing project, scientists have found odors detectable from corpses even after 17 years. "Even bone has odor," Vass said. Moreover, "you can even tell apart different species of animals based on the odor."
Vass and his colleagues have narrowed down 30 simple molecules specific to buried human bodies that are consistently detectable across a variety of soil types and depths.
"The most interesting ones are the fluorinated ones," Vass told LiveScience. "We think these come from a lifetime of drinking fluorinated water and incorporating fluorine into our tissues and bones. As the body breaks down, it releases these compounds, which are very easily detected, since they are very light and come up through the soil easily."
Police investigators often use canines dubbed "cadaver dogs" to sniff out buried corpses, which can prove expensive to train and maintain. "They're very good when they work, but they're living, breathing creatures, and they can get tired," Vass said. Plus, accuracy may vary from dog to dog. Other techniques to locate concealed bodies include ground-penetrating radar, which is tricky to use, or by search teams, which are very labor intensive and often don't cover a lot of area.
Vass explained this research could help come up with chemicals to help train cadaver dogs more effectively. It could also lead to "electronic noses" which are already under development for other tasks, to sniff out corpses without dogs.
"The idea is to have a handheld walkie-talkie-type device, with a snorkel at the top that draws air in with a pump, to concentrate and then analyze samples," Vass said.
Vass and his colleagues plan to submit their most recent findings to a scientific journal this month.