The FBI investigators in protective gloves, boots, and coveralls weren’t quite sure what they would find behind the padlocked chain-link fence on a wooded hillside in Tennessee, except that there would be lots of dead bodies.

The special agents and analysts were students in the FBI Laboratory’s Recovery of Human Remains course, held in March every year by the Forensic Anthropology Center at the Anthropology Research Facility in Knoxville. The outdoor site—popularly known as the “Body Farm”—consists of 2.5 shady acres where human donors are buried, partially covered, or left out in the elements so forensic anthropologists can study how bodies break down and decompose under different conditions. The research facility was established in 1981 with the first body donor. The FBI Laboratory began sending personnel to the Body Farm two decades ago to better understand the intricacies of investigating outdoor crime scenes.

“All of the research that we do out here is to benefit law enforcement and to move forensic science forward in areas such as grave recognition and how best to excavate burials,” said Dawnie Wolfe Steadman, director of the Forensic Anthropology Center at the University of Tennessee, Knoxville, who manages the research facility. To duplicate real-life scenarios, donors are left to decompose in various states—partially clothed, wrapped in plastic, placed in a car trunk, or in a garbage bin. “These are all things we can test,” Steadman said, “and directly help law enforcement figure out their cases better.”