Estimation of postmortem interval using thanatochemistry and postmortem changes

Introduction: Estimation of postmortem interval is an important goal in forensic medicine. After death, many physiochemical changes occur in a regular sequence and can be used to arrive at an approximate time of death. Thanatochemistry is the chemistry of death. It can give a quantitative measurement to determine the postmortem interval (PMI). The aim of the present work was to estimate the time since death using a scoring method for three postmortem changes; hypostasis, rigidity and corneal turbidity. Also, to evaluate the use of thanatochemistry; potassium (K^+) and hypoxanthine (Hx) levels in vitreous humor (VH) in determination of (PMI) and compare the accuracy of thanatochemistry and the scoring method for postmortem changes in estimation of PMI. Subjects and methods: The study was conducted on 70 adult autopsy cases, of known postmortem interval. The development of postmortem rigidity, hypostasis and corneal turbidity was assessed and numerically scored. The potassium (K^+) and hypoxanthine (Hx) levels in vitreous humor (VH) were measured. The data were statistically analyzed and linear regression analysis was used to obtain equations for calculation of PMI. Results: All the studied variables in the present study were significantly correlated with PMI; the highest correlation coefficient was for corneal turbidity, followed by K^+ level in VH then hypostasis, rigidity and lastly hypoxanthine level in VH. Five equations obtained from the present study can predict PMI but with different levels of accuracy. Conclusion: The most accurate equation was that concerning with all the five studied variables (the three postmortem changes in addition to K^+ and Hx levels in VH). Furthermore, the scoring method for the physical postmortem changes was proved to be more valuable in PMI estimation than thanatochemistry within the studied range of PMI that was up to 60 h.