The results confirm the effectiveness of the commercial products for casework applications, particularly the PowerPlex-Y and Y-Filer systems. All systems performed well with 1-3 ng of male DNA as recommended by the manufacturers. All systems gave full profiles at 100 pg of input DNA, which is within the realm of low copy number DNA analysis. Moreover, all except Y-Plex 12 gave full profiles with 30-50 pg of male DNA. When up to 1 mg of female DNA was used (in the absence of male DNA), no female DNA cross reactivity was observed with the Y-Plex 12 and Y-Filer systems. All systems were able to detect the minor alleles in male/male DNA admixtures at a 1:5 dilution, with the PowerPlex Y and Y-Filer being able to detect some minor alleles at 1:20. All Y-STR multiplex systems tested were able to produce complete Y-STR profiles from bloodstains and semen stains exposed up to 6 weeks when the samples were protected against precipitation and sunlight. Complete Y-STR profiles of the male donors up to 72 hours after intercourse were obtained with all of the multiplex systems tested, except for Y-Plex 12, which produced partial profiles. The study evaluated the sensitivity, specificity, and stability of the Y-STR markers used and the ability to obtain a male profile from samples taken at various time points after intercourse. 7 tables, 3 figures, and 20 references