Precision of estimating the time since death using different criteria of supravital muscular excitability

Abstract

Supravital electrical excitability of skeletal muscle is an important method of estimating the time since death in the early postmortem period, which further narrows down the limits of death-time estimation resulting from body cooling. Compared with the subjective grading of muscular excitability, the precision of death-time estimation could already be raised by objectifying the muscular contraction. Criteria for extrapolation of the time since death by objectified muscular contraction are decrease of the maximum force using definite stimuli, increase of the relaxation time, and increase of the galvanic threshold.In an original investigation comprising 71 cases, the first 50 served as reference, whereas the remainder served as the control sample.To re-evaluate the data on the precision of death-time estimation the data was remodeled and matched reference and control samples regarding beginning of the investigation and duration of electrical excitability, age, and so on, were formed. Twenty-eight cases were available for matched reference and control samples. For the reference group, calculations on the accuracy of death-time estimation were carried out and were checked with the independent control group. The following questions were examined on these remodeled reference and control samples: 1. Would death-time estimation be more precise when using the postmortem interval as a dependent or independent variable? 2. Are there any differences between contralateral muscle groups? 3. Are there differences between muscles in the duration of electrical excitability? 4. Can the original data on the precision of death-time estimation be confirmed on the remodeled reference and control sample? The most relevant new result is that when using the postmortem interval as a dependent variable, a much higher precision of death-time estimation can be achieved. There are no differences between contralateral muscles as far as the criteria for extrapolation of the time since death are concerned and the thenar and hypothenar muscles are excitable over a much longer period of time than the biceps bracchii muscle.