The study found that the qRT-PCR assays used are 5-fold to 40-fold more sensitive than a capillary electrophoresis (CE) analysis for body fluid identification. Specificity is maintained over a wide range of RNA input concentrations (20 fg-500 ng). Normalization of both body fluid-specific genes to the housekeeping gene GAPDH by means of appropriate cycle threshold metrics ensures the high specificity of each assay for its cognate body fluid. The body fluid-specific genes included crythroid delta-aminolevulinate synthase (ALAS2) and beta-spectrin (SPTB) for blood, statherin (STATH) and histatin 3 (HTN3) for saliva, protamine 1 (PRM1) and protamine 2 (PRM2) for semen, and matrix metalloproteinase 7 (MMP7) and matrix metalloproteinase 10 (MMP10) for menstrual blood. Body fluids were collected from healthy individuals. The description of materials and methods addresses body fluid samples, RNA isolation and quantitation, cDNA synthesis, standard end-point PCR, real-time PCR primer and probe design, and real-time PCR. 2 tables, 5 figures, and 17 references