BackgroundEstimation of time since death/postmortem interval (PMI) forms a crucial component for all autopsy surgeons. With the subjectivity that is prevalent with conventional morphological and physical signs of death, newer-age modalities such as chemical analysis provide better precision. The easy accessibility and the resistance to putrefaction make vitreous humor the best choice for such chemical analysis. Thus, the present study's aim is to estimate the time since death in cases of unnatural death by investigating the potassium level changes in the vitreous humor.MethodologyThis is a facility-based cross-sectional study conducted in the mortuary under the Department of Forensic Medicine in a public tertiary healthcare teaching hospital in South India between August and September 2022. Deceased individuals fulfilling the inclusion and exclusion criteria were recruited in the study. Vitreous samples were collected from a single eye and analyzed using an autoanalyzer for potassium values. After due derivations, postmortem intervals were calculated from potassium values, then they were compared with the PMIs estimated using physical signs and those determined using official police records. Data were entered using MS Excel 20 (Microsoft Corporation, Redmond, Washington) and analyzed using the Statistical Package for the Social Sciences (SPSS) software, version 20 (IBM Corp., Armonk, NY).ResultsOf the 100 deceased individuals included in the study, 68% were men, and the majority (24%) belonged to the age group of 53-62 years. A linear relationship is said to exist between vitreous potassium concentration and postmortem interval. No correlation was seen between the ambient temperature and the potassium levels of the vitreous humor. PMI confirmed by the potassium levels seconded the PMI given by the police records and physical signs (Rigor mortis) (Spearman’s rho was statistically significant at the two-tailed level or at the 0.01 level with a kappa value of 0.88).ConclusionPotassium measurements in the vitreous humor to estimate the PMI are associated with improved accuracy and precision in determining the time since death. They are not affected by external factors, making them a reliable marker for the same.