ORNL's Arpad Vass found that a dead body lying on the surface or in a shallow grave emits more than 400 different chemical vapors, some of which attract cadaver dogs.
Human body odor historically has a bad name, but for ORNL's Arpad Vass, determining the chemical composition of human body odor after death could lead to the invention of a desirable "electronic nose." Such a detector could help police more quickly find bodies buried in hidden, shallow graves.
A tool that mimics a cadaver dog's nose is high on the wish list of law enforcement agencies. The wish is a goal for Vass, who is close to developing a superb training tool for cadaver dogs and eventually a detector of clandestine graves.
Vass, an expert at determining how long someone has been dead, is also developing a way to calculate "time since death" by reading the peaks of activity of different microbes associated with human decomposition. Recently, he developed a chemical technique for pinning down the day that any murdered victim dies, provided that medical examiners send him organ tissues for the analysis of amino acids and neurotransmitter breakdown products.
The FBI's technology-assisted search teams are deployed many times each year looking for clandestine graves of alleged murder victims, based on tips from informants. The teams use ground-penetrating radar and cadaver dogs in a sometimes futile but always expensive search over a large area.
"It is reported that cadaver dogs can find human remains hundreds of years old and can differentiate human bones from animal bones," Vass says. "However, these dogs are difficult to train, expensive to maintain, and easily distracted. If we could develop a detector that does what cadaver dogs do well, the costs to and efforts of law enforcement would be significantly reduced."
Police could use a tool for quickly distinguishing between human and animal bones because bones are brought to them frequently. "They need to know whether it's a chicken bone or a bone of a dead infant and whether the bone is evidence of a murder," Vass says. "One possible tool we are testing that may detect differences in the elemental composition of human and animal bone is laser-induced breakdown spectroscopy."
At the University of Tennessee Anthropological Research Facility (dubbed the Body Farm), Vass and his colleagues found that donated dead bodies lying on the surface or buried in shallow graves emitted more than 400 different volatile compounds. The researchers are honing in on groups of chemicals that are consistently emitted for each stage of decomposition: fresh, bloated, decayed, and skeletonized.
"We identified fluorinated compounds coming out as vapors from buried bodies," Vass says. "Since Americans drink fluorinated water, it may be possible that, as dead bodies decompose, fluorine combines with hydrocarbon compounds, generating an odor. We'd like to test whether cadaver dogs key in on these compounds."
At the UT facility, ORNL researchers collect vapors from a 2.5-ft-deep grave outfitted with perforated pipes, sampling ports, a video camera for visual monitoring of a body as it decomposes, and a capture hood containing a triple-sorbent trap system developed in ORNL's Chemical Sciences Division—a metal cylinder loaded with carbon granules that bind lightweight, medium-size, and large molecules. The collected vapors are desorbed from the carbon trap and analyzed by a gas chromatograph mass spectrometer at ORNL.
"We found that a human body in a shallow grave decomposes eight times slower than a corpse left on the surface," Vass says. "Some reasons may be that bacterial decay in the body slows down because of the lack of oxygen, and insect infestation of the body is minimal."
If the chemicals that attract cadaver dogs can be identified, then one type of detector that ORNL researchers could build would use polymers that react with specific chemical vapors wafting by. A reaction changes each polymer's electrical conductivity enough to produce an electronic signal. Thus, a specific group of signals from the electronic nose could alert law enforcement that a shallow grave is nearby.
From this research, Vass and his colleagues hope to complete a "DOA" database, where DOA stands for "decomposition odor analysis," not "dead on arrival."
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