Estimating the postmortem interval using microbes: Knowledge gaps and a path to technology adoption

Microbes have potential to be used as physical evidence for forensic science because they are ubiquitous and have predictable ecologies. With the advent of next generation sequencing technology and the subsequent boost to microbiome science (study of the genes and molecules of microbial communities), it has become possible to develop new microbial-based tools for forensic science. One promising approach is the use of microbial succession during the ecological process of decomposition to estimate the time since death, or postmortem interval (PMI). This microbial clock of death is developed by building a regression model using microbiome data collected from postmortem samples (e.g. swab of skin) with known PMIs. In a death investigation, a similar sample type (e.g. swab of skin) would be collected, the microbes profiled using DNA sequencing, and the microbes would be matched to a point on the clock (i.e. the regression model). Recent research by several independent scientific teams has provided a proof of concept for this new microbiome forensic tool. However, developing and transitioning new forensic science technologies into the justice system requires overcoming scientific, investigative, and legal hurdles. In this article, I address the apparent knowledge gaps in the science of microbiome technology to estimate PMI, and discuss a path for bringing this technology into the justice system.