Outer ear temperature and time of death

Abstract

From a research sample of 138 corpses, divided into four subgroups of ambient storage temperature (0–5 °C, 6–10 °C, 11–15 °C and 16–23 °C) four linear regression formulae of actual versus estimated post-mortem interval were obtained (‘interval’ formulae) using a single outer ear temperature measurement on both sides. This method showed the best correlation coefficient among five other methods previously proposed for time of death determination (rectal temperature, vitreous K +, CSF K +, blood log Na + K + and log Cl −), however its results were less accurate than those obtained with a multivariate equation combining several of the above mentioned methods. Eventually an equation expressing time of death (TOD) as a function of outer ear temperature (OE T °) and ambient temperature was also established from the whole research sample (‘global’ formulae). On a different sample of 141 corpses the regression formulae (‘interval’ and ‘global’) for the outer ear temperature were compared to three methods based on a single rectal temperature measurement (‘rule of thumb’ 1 and 2, Henssge nomogram) and therefore useful at the scene; the results of all methods were compared within the four subgroups of ambient temperature as well as in three subgroups of different post-mortem interval lengths (<7 h, <10 h, <15 h). In all cases the outer ear temperature formulae provided better results than the rectal temperature methods (especially Henssge nomogram and rule of thumb 1). Moreover they did not show any post-mortem plateau which was present in almost 30% of cases when rectal temperature was measured in corpses kept at ambient temperature above 15 °C. Our results show that outer ear temperature measurement is the method which provides the best simplicity/quality ratio and should therefore be proposed for use at the scene when conditions are similar to those of our experiment (within buildings). A software equipped thermometer is required in order to use in each case the appropriate formula and confidence interval.