Biochemical Parameters for Estimating Time of Death

Background: The estimation of the time of death, also known as postmortem interval (PMI) plays an important role in the investigation of homicides and other crimes relating to death. Death results in very extensive biochemical changes in all body tissues due to cellular degradation, altered enzymatic reactions, and cessation of all metabolic processes. A careful analysis of the biochemical changes that occur after death may help in estimating the actual time of death.

Methods: A total of fifty (50) cadavers where exact time and causes of death were known and without electrolytes and diuretics given prior to death were recruited for this study. Vitreous humour potassium, sodium, chloride and bicarbonate were analyzed using ion selective electrode system (ISE 4000).

Results: There was a statistically significant difference between the vitreous fluid potassium and bicarbonate levels of the cadavers that died within 48 hours and those that died after 48 hours (P-value 0.028 and 0.001 respectively) but there was no significant difference between the vitreous fluid sodium and chloride of cadavers that died within 48 hours and those that died after 48 hours (P-value 0.369 and 0.100 respectively). There was a positive correlation coefficient between potassium and PMI (r=-0.404) and negative correlation coefficient between bicarbonate and PMI (r= -0.339) within 48 hours after death.

Conclusion: In this study, we demonstrated that the concentrations of vitreous humour potassium and bicarbonate can be used to determine the time of death. We recommend that the scope of this study should be extended to determine the rate of increase in the concentration of vitreous humour potassium and decrease in the concentration of vitreous hummour bicarbonate.