[Quantimetric investigations of the time of death by estimating the postmortem threshold (rheobase) of human skeletal muscles to electric stimulus by direct current (author's transl)].

We recently reported on an unusually high correlation between the post mortem interval and the postmortem (pm) increase of the muscular threshold to galvanic stimuli (Rheobase) in the skeletal muscle of the rat. To find out whether a practicable method of estimating the time of death could be developed out of this, we investigated skeletal muscles of 11 individuals having died from various causes. The muscles were stimulated electrically by square-impulses of 1 s length at 200 V, the strength ranging from 0.1 to 80 mA. The electrodes were applied to the skin. A strong correlatin (r = 0.98 on average) between the muscular threshold to electric stimuli and the time of pm investigation was also found in human muscles and can be described by the Formula Y(T)[mA] = A*Exp(b . T) when A* is the primary threshold (Rheobase) and T the time of pm interval. Differentiation of this equation leads to a strongly linear regression curve by which finally the time of death can be expressed as (formula: see text). The coefficients a0 and b can be calculated by the linear regression of the pm Rheobase in a semi-logarithmic system of coordinates and a* as lnA* [mA] from the course of the regression curves--a0 = lnA0 [mA] at the beginning of the investigation and b [l/min] = gradient of the regression. The testing of the muscles flexor digiti V and flexor digitorum communis brevis, in particular, lead to the most exact results. By this method immediate results of hitherto unknown reliability can be achieved in estimating the time of death up to 15 h postmortem by statistical means of calculation. Changing temperatures, different causes of death, and other individual factors seem to be of no influence on the results so that collectives of known characteristics are not necessary for comparison.