A Multidisciplinary Validation Study of Non-human Animal Models for Forensic Decomposition Research

As submitted by the proposer: The past three decades of human decomposition have demonstrated that certain factors promote decomposition, such as high temperatures and insect access, yet the rate of decomposition varies considerably in macro- and microenvironments. The Anthropology Research Facility (ARF) at the University of Tennessee was the first to utilize human cadavers to document decomposition in a variety of controlled settings, laying the foundation for human decomposition research. Not all researchers have access to human cadavers, however, and therefore have employed nonhuman animals as surrogates for humans in decomposition studies. The results from some of these animal model studies have been used in the courts to support postmortem interval estimations of human decedents. Nonetheless, the scientific validity of substituting data from nonhuman carcasses for human cadavers has enjoyed limited evaluation. The proposed project will directly compare the decomposition dynamics of humans and two animal models often used in decomposition research pigs and rabbits. Human, pig and rabbit subjects will be placed simultaneously in the same ecological niche within the ARF to ensure soil and environmental conditions are identical for all subjects. Five subjects of each species will be studied in three separate trials in which season and microenvironment will vary. Our multidisciplinary data will include not only systematic visual observations of the primary decomposition stages, but also arthropod diversity on and around the subjects. We will utilize a quantitative scoring method of gross decomposition and insect taxonomy tied to a temperature-dependent time scale, accumulated degree hours (ADH) to provide a comprehensive picture of how body size and biological composition influence decomposition. Ultimately we will determine whether, in the same settings, pig and rabbits are appropriate analogs for humans in terms of decomposition research and estimates of postmortem intervals. Well-designed validation studies are at the heart of basic scientific research and are specifically requested in the recent National Academy of Science (NAS) report as a means to elevate the scientific merit of forensic practice. Our multidisciplinary validation study of the performance of nonhuman models for decomposition research will provide the first scientific verification or refutation that pigs or rabbits can serve as proxies for human decomposition in forensic contexts. The outcomes of the study will impact how future research is conducted with regard to animal proxies as they relate to entomology and anthropology for postmortem interval estimation. Our multidisciplinary approach has a high probability of stimulating future applied work in forensic chemistry, biology, and soils analysis in postmortem interval estimation. Our deliverables include journal articles, conference papers and lectures in the Forensic Anthropology Centers annual short courses provided to law enforcement and medicolegal personnel as well as rising students in forensic science. ca/ncf