COMPARATIVE UTILITY OF RIGOR MORTIS, LIVOR MORTIS AND RECTAL TEMPERATURE IN ESTIMATION OF EARLY POSTMORTEM INTERVAL: A PROSPECTIVE OBSERVATIONAL STUDY

Abstract

Background:  Estimation of the postmortem interval (PMI) is one of the most important and challenging components of medico-legal investigation. Conventional postmortem changes such as algor mortis, rigor mortis and livor mortis are routinely used for estimating time since death, particularly during the early postmortem period. However, their reliability is influenced by environmental temperature, humidity, clothing, body habitus, cause of death and other biological factors. Recent evidence emphasizes that no single postmortem parameter should be interpreted independently and that combining multiple indicators may improve the accuracy of PMI estimation.

Materials and Methods:  A prospective observational study was designed involving 150 medico-legal autopsy cases in which the time of death was reliably documented. Rectal temperature, ambient temperature, degree and distribution of rigor mortis, and characteristics of postmortem lividity were recorded at the time of examination. Cases with advanced decomposition, severe thermal injury, prolonged refrigeration, unknown time of death or major disruption of postmortem changes were excluded. The estimated PMI derived independently from each parameter was compared with the documented PMI. Mean absolute error, correlation coefficients and the proportion of cases estimated within ±2 hours of the documented PMI were calculated. Paired comparisons and multivariable regression were performed. A p-value <0.005 was considered statistically significant.

Results:  Among the 150 cases, 108 (72.0%) were males and 42 (28.0%) were females. The mean age was 41.8±17.6 years. Rectal temperature showed the strongest inverse correlation with PMI (r=-0.78, p<0.001), followed by rigor mortis score (r=0.71, p<0.001) and livor mortis progression (r=0.64, p<0.001). The mean absolute error was lowest for the combined model (2.1±1.7 hours), followed by rectal temperature (3.0±2.3 hours), rigor mortis (3.7±2.8 hours) and livor mortis (4.1±3.0 hours). The combined approach estimated PMI within ±2 hours in 76.0% of cases compared with 58.0% for rectal temperature, 49.3% for rigor mortis and 42.7% for livor mortis (p<0.001).

Conclusion:  The findings suggest that rectal temperature, rigor mortis and livor mortis each provide useful information during early PMI estimation, but their combined interpretation provides greater accuracy than reliance on any single parameter. Environmental and individual variables should be considered when interpreting traditional postmortem changes.