Electrical conductivity of synovial fluid as a measure of death time in late postmortem examination

Abstract

BACKGROUND: The determination of time since death is of significant legal importance, because the findings of investigation of a crime against the life and health largely depends on the successful resolution of this issue. The determination of time since death becomes particularly significant in cases where the death circumstances are not evident and the cadaver is examined in the late postmortem period. Without conclusive evidence of a non-violent death, investigators assume homicide; the exact death time since death serves to narrow the options and confirm or refute this assumption. The putrefaction complicates the forensic examination, limiting the accuracy of answers to the investigator's questions and requiring the new objective expert criteria search.

AIM: To assess changes in electrical conductivity of synovial fluid of knee joints at the stage putrefaction with mathematical description of the revealed changes on the basis of a multilayer perceptron to substantiate the prospects of determining the time since death by conductometric method.

MATERIALS AND METHODS: Conductometric properties of synovial fluid of knee joints of 103 cadavers who died of various causes at the age of 20–87 years were studied. The study was performed in the late postmortem period (up to 10 days). The time since death was established comprehensively considering medical, forensic and investigative data. The electrical conductivity was measured using AKIP RLC 6109 measuring system, with an error of 0.1%, at frequencies of 0.1 kHz, 1 kHz, and 10 kHz.

RESULTS: Electrical conductivity of synovial fluid at 100 Hz and 1 kHz was found to depend significantly on the time since death. The optimal mathematical model describing this correlation is a second degree polynomial. A model with a 2-5-1 multilayer perceptron architecture is also presented with an error that does not exceed the set limit (reliability >95%).

CONCLUSIONS: Conductometric analysis of synovial fluid of cadavers’ knee joints in the late postmortem period allows to reliably detect changes in its electrical conductivity determined by the time since death. These changes can serve as a mathematical model basis for calculating the time since death in the late postmortem period. The most accurate predictions are provided by model No. 2 with a 2-5-1 multilayer perceptron architecture, making it the most suitable for this task.

Keywords

electrical conductivity / synovial fluid / knee joint / time since death / late postmortem period / mathematical model / multilayer perceptron

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