Until the early 1980s, investigators had little hard data on how a human body decays outdoors, so time of death in a shallow grave was often guesswork. In 1981 William Bass, head of anthropology at the University of Tennessee in Knoxville and the state’s forensic consultant, fenced off a wooded plot behind the medical center and began placing donated bodies in car trunks, water, plastic, and open sun. He tracked the stages from fresh to bloat, active decay, and skeleton, and how clothing and sunlight change the timeline. Neighbors protested, forming a group called SICK, but the data began solving cases.

Eight US facilities now cover different climates, from humid southeast Texas to arid Colorado Mesa University, where bodies tend to mummify, to the 26 acre site at Texas State University’s Freeman Ranch. Fears about vultures near an airport there turned into research showing the birds can skeletonize a body in hours and leave marks resembling knife wounds. An Australian facility near Sydney used time lapse cameras to show bodies move as ligaments dry. The episode also covers Sue Black’s case for pig proxies and Jennifer DeBruyn’s work on the necrobiome as a microbial clock in the soil.

• Why a Knoxville decay model fails in the mountains of Colorado or the Texas heat
• How vultures scatter bones downhill and into trees
• What pigs cannot replicate: medications, chemotherapy, implants, and human weapon trauma
• Over 100 donated bodies a year at Tennessee, about 60 percent arranged by families
• Patricia Cornwell’s novel The Body Farm and a character based on Bass