This dissertation provides the first quantitative estimate of postmortem interval of terrestrially decomposed human skeletal remains using microbial abundance information.
Human decomposition is a dynamic process partially driven by the actions of microbes. The microbial communities that facilitate decomposition change in a predictable, clock-like manner, making it a forensic tool for estimating postmortem interval. Chapter 1 also describes which sample types are most useful for predicting postmortem interval based on the stage of decomposition. During fresh and early decomposition, microbial succession of the skin and soil sample types are most predictive of postmortem interval; however, after approximately the first three weeks of decomposition, the changes in the microbial communities that are used for predictions begin to slow down and the skin and soil sample types become less useful for estimating postmortem interval. Chapter 2 shows that microbial succession of the bone microbial decomposer communities can be used for estimating postmortem interval during the advanced and skeletonization stages of decomposition and summer seasons at the Southeast Texas Applied Forensic Science Facility. Chapter 3 of this dissertation focuses on the influence of the blow fly (Calliphoridae) microbiome on human cadaver microbial community assembly. First, Chapter 3 shows the characterization of the blow fly microbiome by organ and season in a terrestrial, human decomposition environment. Results showed that the previously defined universal fly microbiome persists even in a decomposition environment, with notable differences still present between organs and seasons. Additionally, results from using the tool SourceTracker2 showed that the labellum and tarsi act as substantial bacterial sources of the human decomposer bacterial community, and this source contribution varies by season.