Postmortem microbiome dynamics: Review of forensic microbial clock

The postmortem interval (PMI) in Forensic science presents several challenges, including accurate investigation, estimation and reliance on a limited set of physical and microbial markers. However, while these methods have advantages, they are also limited by factors such as environmental variability and temporal constraints. Microbial succession during decomposition, commonly referred to as the "microbial clock", has emerged as a promising and potentially more precise indicator of PMI. It is clear from a thorough examination of more than 30 peer-reviewed studies involving human cadavers and animal models that microbial communities undergo predictable, time-dependent internal and external changes. Controlled studies using murine and porcine models have demonstrated strong temporal correlations between specific microbial taxa and distinct stages of decomposition, with some models capable of predicting PMI within a two-to-three-day accuracy range over several weeks. Similarly, studies on human cadavers have shown consistent patterns of microbial succession within postmortem organs, revealing organ-specific microbial signatures that change over time and can be influenced by variables such as the cause of death, the environment and the health of an individual. These findings suggest that microbial succession can serve as a powerful quantitative and biological tool for determining the time of death. However, to realize its full potential, further research is needed, using diverse datasets and incorporating multiple post-mortem indicators. This review provides a comprehensive summary of current knowledge on the microbial clock and discusses the ecological and practical considerations necessary to develop a robust and reliable post-mortem clock for forensic practice.