In an advance toward the first portable device for detecting human bodies buried in disasters and at crime scenes, two Penn State forensic scientists report early results from a project to establish the chemical fingerprint of death. According to Dan Sykes, senior lecturer and director of analytical instructional laboratories at Penn State and the project's leader, "Acertaining a profile of the chemicals released from decomposing bodies could lead to a valuable new addition to the forensic toolkit: an electronic device that could determine the time elapsed since death quickly, accurately, and onsite." The team is presenting its research in a poster at the 238th National Meeting of the American Chemical Society at 7:00 p.m. on 16 August 2009.
Today, cadaver dogs are the gold standard for detecting and recovering bodies in earthquakes, tornadoes, hurricanes, and other natural disasters. "These dogs are highly effective, but it takes a lot of time, money, and manpower to train them," said Sykes. "A device that is as effective as dogs, but is a fraction of the cost, would be something worth pursuing."
With a goal of developing such a device, Sykes and his graduate student, Sarah Jones, are working to identify the gases that are released as bodies decompose under a variety of natural environmental conditions. The team also is measuring the time sequence in which odorant chemicals from dead bodies are released in the hours and days after death. "What we're looking for is the profile of what gases are released when we die, as well as how the environment and the manner in which we die affects this profile," said Jones.
Decomposing bodies release more than 30 compounds. Some, like the aptly-named "putrescine" and "cadaverine," develop early in the decomposition process. Past studies used donated human bodies that were two to three days old to measure decomposition vapors. As a result, these studies were unable to detect putrescine, cadaverine, and other compounds that appear very early in the decomposition process. By using pigs euthanized under human conditions, Jones and Sykes are able to study decomposition immediately after death.
"Pigs are good models for this research," said Jones. "They go through the same phases of decomposition as humans, as well as the same number of stages. And those stages last about as long in pigs as they do in humans before complete decomposition occurs and only the bones remain."
In one experiment, Sykes and Jones placed dead pigs in specially designed odor-collecting units under a variety of environmental conditions. Above each specimen, they affixed special sensors known as solid phase micro extraction (SPME) fibers to capture the gases. These specially-coated fibers are widely used to sample the chemical composition of air. The team collected odor data every six to 12 hours over the course of a week -- longer than any other study of this kind.
Studying the week's worth of odor data, a clear chemical profile emerged. "In days one through three, we found precursors to a compound called endol. On day three, we found endol and putrascine, the main compounds that we were trying to detect," said Jones. The scientists now are capturing gases released in a variety of other scenarios to re-construct the different ways human bodies could decompose, creating a more complete picture of decomposition.
This research received financial support from the Penn State Eberly College of Science, as well as laboratory supplies and materials from the American Analytical company in State College, Pennsylvania.
[ Adam Dylewski / Sara LaJeunesse ]