Determination of the Late Postmortem Interval by Observing the Electrical Conductivity in Skeletal Muscles of Rats.

Objective: To determine the values of electrical conductivity (EC) of cadaveric skeletal muscles of male rats and their relationship with different postmortem intervals (PMI).

Study design: Experimental study. Place and Duration of the Study: Department of Forensic Medicine and Toxicology, King Edward Medical University (KEMU), Lahore, in collaboration with the University of Veterinary and Animal Sciences (UVAS) Lahore, from October 2021 to September 2022.

Methodology: The non-probability consecutive sampling technique was used for the sample collection of 98 Sprague-Dawley rats and all were male. All lower-hind limb skeletal muscles of rats with known death intervals were used. Parameters (EC) were measured by using conductivity meter DDS-11A, through the method described by Ekanem and Achinewhu. Healthy adult rats within a specific weight range (250-300 g) and with a known time of death, euthanised using a standardised method such as CO2 asphyxiation were included, and the rats with pre-existing diseases or injuries affecting muscle tissue, those showing advanced decomposition or bacterial contamination, or with an unknown or inconsistent PMI were excluded.

Results: The results showed that there was a significant correlation between the duration of PMI and EC, and the data fitted well in the quadratic regression equation as y = -1203.67 + 2.50 EC + 0.001x2 (R2 = 0.924).

Conclusion: This study suggests that measuring the EC of skeletal muscle extracts offers a reliable method for estimating late PMIs, showing a strong correlation with PMI duration and providing a valuable forensic tool.

Key words: Postmortem interval, Electrical conductivity, Skeletal muscles, Postmortem changes, Muscle conductivity.