Confidence intervals in temperature-based death time determination

• Death time determination (DTD) is a central competence in legal medicine.
• Marshall and Hoare Method with Henßge parameters (MHH) is widely used in DTD.
• Probability of 95%-confidence intervals (CI) of MHH is reduced by bias.
• In the article formulae are derived for real CI probability under bias.
• Corrected CIs can be computed by formulae in this article.

Marshall and Hoare’s double exponential model with Henßge’s parameters is a well known method for temperature based death time estimation. The authors give 95%-confidence intervals for their method. Since body cooling is a complex thermodynamical process, one has to take into account a potential bias of the estimator. This quantity measures the systematic error of the estimators underlying model. For confidence interval radius calculation a bias of 0 is presupposed, therefore the actual probability of the true death time value to lie in the 95%-confidence interval can be much lower than 95% in case of nonvanishing bias.As in case of nonstandard conditions the confidence intervals have a probability of containing the true death time value which even in case of small corrective factor errors of Δc = ±0.1 can be substantially smaller than the 95% claimed, the paper presents a formula for confidence intervals which keep a 95% probability in case of error Δc ⩽ ±0.1.