Temporal and spatial RNA expression dynamics in postmortem skin support PMI estimation and reveal spatial signatures of antemortem injury

RNA expression dynamics have emerged as a promising focus in forensic research; however, their practical applications remain limited. In this study, we focused on skin, a biologically stable, forensically practical, and accessible tissue, to characterize postmortem and injury-related RNA expression dynamics and explore their forensic relevance. First, under well-controlled experimental conditions, mouse skin was analyzed up to 8 h postmortem using transcriptomic profiling. Genes exhibiting characteristic time-dependent expression patterns were identified, and a postmortem interval (PMI) estimation model achieved a coefficient of determination of 0.900 and a root mean squared error of 0.894. These findings were subsequently examined in human autopsy skin samples, where several RNAs demonstrated temporal expression changes consistent with those observed in mice. Beyond the initial 8-h transcriptomic analysis, similar expression dynamics in mice were further validated up to 72 h postmortem, partially confirming RNA dynamics shown in human samples. In particular, EGR1 and FOS showed expression patterns consistent with their known functions in the stress response. Furthermore, spatial transcriptomic analysis of injured skin revealed region-specific gene expression alterations according to wound proximity and tissue layer (epidermis and dermis). These patterns were evident specifically in antemortem injuries when compared with postmortem injuries, potentially distinguishing antemortem from postmortem injuries in autopsy samples. In summary, our findings indicate that the skin RNA expression exhibits characteristic temporal and spatial dynamics following death and injury. Understanding these molecular time- and place-dependent changes may provide supportive information for PMI estimation and injury assessment in forensic practice.