An Alternative Method to Measure Glucose and Lactic Acid as Biomarkers of the Postmortem Interval (PMI)

Background: In forensic investigations, the postmortem interval (PMI) is still mainly determined using pathological analysis. There have been many scientific efforts to identify alternative methods of PMI determination, which may be applied to future forensic practices. Methods: Considering the ethical implications and the availability of tissue samples for PMI experiments, we used human blood samples stored at three temperatures to mimic different environmental conditions, testing them over a period of 10 days post-sampling. These samples were biochemically tested for specific blood biomarkers, glucose (Glu) and lactic acid (Lac), to determine their potential as PMI biomarkers. Then, a mixed-effect mathematical model was applied to the data related to time- and temperature-dependent concentration changes of both biomarkers followed by additional computer-simulated models to refine the PMI estimates based on each of the biomarker concentration changes. Results: Herein, we present this alternative method of PMI estimation based on the biochemical testing of blood samples that could potentially be collected at a crime scene using biochemical blood biomarkers Glu and Lac, which are mathematically modelled and refined with time- and temperature concentration changes. Conclusions: While there is still much forensic science required to validate any alternative PMI methods, this study shows that there are other cross-disciplinary methods of PMI determination that warrant further exploration.