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 identified the piR-hsa-18287 as an absolute specific marker for venous blood, demonstrating high specificity in pairwise comparisons and moderate expression levels [Liu et al. DOI:10.3390/genes13091530].