NCJ Number
138361
Journal
Journal of the Forensic Science Society Volume: 32 Issue: 2 Dated: (April/June 1992) Pages: 117-129
Date Published
1992
Length
13 pages
Annotation
This study sought to produce an accurate, standardized, and reproducible method of assessing the contraction of skeletal muscle after death by means of electrical stimulation and relating muscle contraction to the time elapsed since death.
Abstract
The sample included 50 experimental bodies and 21 control bodies, all cases of sudden natural or traumatic death with a short terminal episode. All investigations were conducted at a constant ambient temperature of 20 degrees C, with continuous measurement of deep rectal and local temperature. Postmortem contraction was measured using sensitive force transducers inserted into human muscle. The muscle was stimulated using rectangular impulses of 1-second duration and known current intensity. After some time, a noticeable change occurred in muscle contraction, from a two-peak to a one-peak shape. The maximum force of muscle contraction using a stable current intensity decreased with time since death, but relaxation time increased. The decrease of maximum force and the increase of relaxation time were used as criteria for extrapolating time since death for the 50 bodies. Calculated 95-percent limits of confidence were 2.85 hours (decrease of maximum force) and 2.7 hours (increase of relaxation time) up to 13 hours postmortem. The 95-percent confidence limits proved to be reliable for the 21 bodies as well. The author concludes that decrease of maximum force and increase of relaxation time represent quantifiable criteria for describing changes in muscular excitability with time. 10 references, 2 tables, and 12 figures