Post-mortem supravital skeletal muscle excitability for early post-mortem interval estimation: a scoping review and methodological map.

Early post-mortem interval (PMI) estimation relies mainly on temperature-based nomograms together with rigor and livor mortis, all imprecise in the first hours after death - a limitation underscored by a recent independent validation of the compound method reporting an overall agreement of only ~ 37%. Post-mortem supravital skeletal-muscle excitability, evoked electrically or mechanically, is a long-standing but fragmented adjunctive marker. This scoping review maps the available evidence and derives the methodological requirements of a future prospective study, addressing the question: what evidence exists on post-mortem supravital skeletal-muscle excitability, induced by electrical or mechanical stimulation, as an adjunctive tool for early PMI estimation? Following the JBI methodology and PRISMA-ScR reporting, a Population-Concept-Context framework defined eligibility. PubMed/MEDLINE, Scopus and Web of Science were searched without language or date limits, with citation searching of key authors. Records were charted along ten predefined dimensions and appraised with study-type-adapted instruments. Twenty-six included records - corresponding to approximately 21 independent contributions after collapsing companion papers and consecutive series that report overlapping datasets - were organised into five streams: objectified/subjective electrical excitability, mechanical idiomuscular reaction, the compound method, post-stimulation structural artifacts, and animal models. Electrical methods provided the most precise estimates (95% confidence limits ~ ± 2.7-±2.85 h up to ~ 13 h) but required invasive instrumentation; mechanical reaction testing was field-deployable but operator-dependent and strongly modulated by biological and environmental factors. Within the compound method, adding non-temperature criteria - including muscular excitability - narrowed the temperature-based interval in roughly two-thirds of scene cases. A recurrent probative caveat is that structural alterations classically regarded as vital can be reproduced post-mortem in the supravital phase. Controlled animal (rat) models complemented the human evidence, characterising the decay of the compound muscle action potential and indicating that its onset latency is comparatively independent of the cause of death. Supravital muscle excitability is a promising adjunctive marker to be standardised and prospectively validated within the compound method, not used as a stand-alone determinant of the time of death. The review specifies the resulting research agenda: a prospective, minimally invasive study in deaths with a certified time of death, with standardised stimulation, objectified outcomes, systematic recording of confounders and internal validation against a temperature-based reference model.