Toward a Universal Equation to Estimate Postmortem Interval

Estimating postmortem interval is an important goal in medicolegal death investigations. Although several methods have been developed to achieve this goal, many of these require significant time and advanced expertise to generate a reliable estimate. Unfortunately these techniques do not provide much insight during the early stages of an investigation when critical decisions must be made regarding the allocation of investigative resources. An equation was recently developed to address this problem: provide a preliminary estimate of postmortem interval to initiate an investigation while more advanced techniques are conducted. To evaluate this equation, we used it to estimate postmortem interval at multiple indoor death scenes with known PMI in Nebraska and Hawai'i. This equation allowed us to accurately estimate PMI at 15 of 19 (79%) indoor death scenes. In Nebraska, this equation was accurate at 100% of the scenes. In Hawai'i, this equation was accurate at 60% of the scenes. All inaccurate estimates of postmortem interval were associated with at least 20% mass loss and a postmortem interval of ≥4 days. Although this equation was accurate at the majority of the death scenes attended, we conclude that more research is warranted, particularly the effect of climate on decomposition and the investigators' ability to accurately estimate soft tissue mass loss.