JENNIFER SYNSTELIEN emerges from the tool shed wearing a knee-length plastic apron, surgical face mask and thick latex gloves. Unfazed by the smell of death wafting through the warm autumn air, she kneels next to a decomposing corpse. Her practised hands wave at hovering flies as she opens the chest cavity and pokes around for the heart with long, stainless steel forceps. It's gone—liquefied after a month of decay. "At this point, I don't know if there are any organs left," she says.

So begins a normal day at the Body Farm, a gruesomely remarkable research facility where 20 or so bodies at a time rot in the open air in the name of forensic science. Synstelien is a forensic anthropology graduate student from the University of Tennessee, and is working with Arpad Vass, a biochemist at Oak Ridge National Laboratory. For more than a decade, Vass and his students ...