Forensic Utility of Vitreous Potassium Concentration in Estimating Postmortem Interval: A Systematic Review

Estimation of postmortem interval (PMI) is a fundamental component of forensic pathology. One of the reliable methods is assessment using biochemical markers such as sodium, potassium, chloride, bicarbonate, and hypoxanthine. Among biochemical markers, vitreous potassium (K⁺) has been extensively studied due to its predictable postmortem changes and relative stability. In comparison to other body fluids, vitreous humor is resistant to early putrefaction changes and is least affected by external factors. A systematic search of PubMed and Scopus databases was conducted using predefined search strategies. Studies involving human subjects, measurement of vitreous potassium, and evaluation of its relationship with PMI were included. A total of 123 studies were identified from PubMed and Scopus; 24 studies met the inclusion criteria and were included. Vitreous potassium demonstrated a strong positive correlation with PMI (r = 0.84-0.99), with most studies supporting a linear relationship within the first 72 hours, although some reported a biphasic pattern. Significant variability in regression models was observed due to differences in environmental conditions, analytical methods, and study populations. Temperature showed inconsistent but notable effects, particularly at extended PMIs, where deviations from linearity reduced reliability. Methodological heterogeneity further influenced results, while recent evidence suggests improved accuracy when potassium is combined with additional biochemical markers such as hypoxanthine and albumin. Vitreous potassium is a reliable marker for estimating PMI, especially in early stages. However, variability limits its standalone accuracy, and integration with multiparameter models is recommended.