Estimation of the postmortem interval using spectrophotometric analysis of putrefactive blister fluid: an experimental study

BACKGROUND: This study addresses the issue of estimating the postmortem interval based on the examination of human remains with signs of putrefactive decomposition. In particular, it involves spectrophotometric analysis of putrefactive blister fluid with subsequent development of a mathematical equation and its use as an additional method for estimating the postmortem interval, which will improve the accuracy and objectivity of forensic conclusions in addressing this issue. AIM: The work aimed to evaluate the possibility of objective postmortem interval estimation using spectrophotometry through analysis and mathematical modeling of changes in the optical density of putrefactive blister fluid in the late postmortem period. METHODS: This was an experimental, uncontrolled, single-center study. The biological material consisted of putrefactive blister fluid obtained during the examination of cadavers of both sexes across different age groups at various stages of the postmortem period with signs of putrefactive biotransformation. Spectrophotometric analysis was performed at the Bureau of Forensic Medical Examination of the Udmurt Republic, Ministry of Health of the Russian Federation, from February 2023 to July 2024 using an SF-2000 spectrophotometer in the wavelength range of 490–520 nm as per the developed protocol. RESULTS: Changes in optical density of the studied fluid obtained from cadavers (n = 77) demonstrated time-dependent changes relative to the postmortem interval, allowing the construction of a mathematical equation based on a power model with an approximation coefficient exceeding 95% for the 24–120 h postmortem interval. Additionally, limits of potential error for the developed equation were calculated, with formulation of a corresponding mathematical inequality. The results were validated using a blinded experimental approach on practical material. CONCLUSION: The findings support the use of optical density of putrefactive blister fluid as a quantitative parameter for estimating the postmortem interval. Considering its temporal changes, the proposed mathematical model may be applied in the 24–120-hour postmortem period as an additional diagnostic tool.