Changes in Microbial Communities Throughout the Body Decomposition Process and Its Potential Application in Forensic Casework

Forensic microbiology consists in the study of microbes as it relates to the civil and criminal law; it is a relatively new field that contains a wide range of applications such as trace evidence, contamination, bioterrorism, food spoilage and authenticity, cause of death investigation, and postmortem interval (PMI) estimation. When death occurs, the body undergoes a series of macroscopical and microscopical changes that can be used to estimate the PMI, which is the time passed since an organism died to the time its discovered, and it is a key information for forensic investigations. After death, the immune system no longer functions, physiological barriers break down, and the composition of local microbiomes shift and translocate to other areas of the body. Moreover, microbial representatives from the environment also take a role in the decomposition process since there is an exchange of environment and cadaver microbial representatives. So, dramatic changes occur in the microbial community's composition in the human body throughout the decomposition process. Studies have demonstrated that the community composition changes predictably over the course of decomposition allowing scientists to exploit this as a potential tool to estimate PMI. This chapter explores the postmortem changes in the microbial communities of the body, discusses the different techniques and methods to analyze these changes, and exposes the current limitations for its application in forensic casework.