A study in humans characterized piwi-interacting RNA (piRNA) expression in six forensically relevant biological fluids and stains (venous blood, menstrual blood, saliva, semen, vaginal secretions, and skin) using massively parallel sequencing [Wang et al. DOI:10.1016/j.fsigen.2019.07.015]. A study in humans demonstrated that the piR-hsa-25783 is a potential biomarker for body fluid identification, showing statistically significant expression differences between at least two types of forensically relevant fluids, with higher expression in semen and vaginal secretions compared to saliva, though it could not distinguish between vaginal secretions and semen [Wang et al. DOI:10.1016/j.fsigen.2019.01.002].