Temperature based forensic death time estimation: The standard model in experimental test

Abstract The determination of the time since death is essential to forensic homicide investigations since the time of death represents the presumed time of the offence. Erroneous death time estimates may lead to false acquittal or conviction of suspects. Since its introduction 30years back, the nomogram method by Hensge has been established as the standard procedure of temperature-based death time determination in the early post-mortem period. The present study provides an independent investigation of the validity of its death time estimates and their corresponding 95%-confidence intervals. Comparison to post-mortem cooling curves recorded under controlled conditions of 84 suddenly deceased with known death times yielded the following results: (1)Violations of the predicted 95%-confidence intervals by the nomogram method were observed in 48 of 84 cases (57.1%). (2)The standard deviations computed from our experimental data considerably exceed those presupposed in the nomogram method for 95%-confidence interval derivation. (3)The nomogram method shows a clear trend to over-estimate the post-mortem interval in cases with high body mass and large surface area. Since in the light of our experiments the validity of the nomogram method seems to be problematic, death time estimates – and particularly their 95%-confidence interval limits – have to be interpreted carefully and should only be restrictively used as court evidence to support or refute alibis. Systematic overestimation of the post-mortem interval in bodies of high mass and large surface area must be taken into account.