This article summarizes the goals and features of three grant projects awarded by the U.S. Justice Department’s National Institute of Justice (NIJ) that focus on the determination of the length of time since death of a body by focusing on the microbes that consume a body after death.
Scientists have long known about the progression of insect populations active on a dead body during the first 2 weeks of decomposition and how such information can serve as a clock for determining how long a body has been dead. In recent years, however, several researchers supported by NIJ grants have sought to extend the length of time that can be determined since death by focusing on the microbes that consume a body after death. During life, the immune systems of human bodies defend against trillions of bacteria, fungi, and viruses in and on the body; however, at death, the human body’s immune system stops functioning, and the body’s interaction with the microbes changes significantly. Microbes inside the body and from the surrounding environment in which a body is located start breaking down organs and other tissue. As decomposition progresses, knowing which microbes appear and when in the decomposition process is the basis for constructing a postmortem microbial “clock.” Microbial clock may cover longer time periods and be a more precise predictor of the postmortem interval than insects. The three NIJ-funded research projects described in this article address 1) estimating the postmortem interval of human skeletal remains using rapid, inexpensive microbiome tools; 2) microbial clocks for estimating the postmortem interval of human remains at three anthropological research facilities; and 3) improving estimates of the postmortem interval with metagenomics and metabolomics.