Collection of body fluid samples Five forensically relevant body fluids were used for initial miRNA TaqMan1 Array screening. Body fluid samples were collected on sterile cotton swabs and dried at room temperature. Venous blood was collected by venipuncture without anticoagulation treatment, and 50 ml aliquots were spotted onto sterile cotton swabs. Freshly ejaculated semen was provided in sealed plastic cups and dried onto sterile cotton swabs. Semen-free vaginal secretions and menstrual blood were collected from the vagina with sterile cotton swabs and dried at room temperature. Saliva samples were provided in sealed plastic tubes and dried onto sterile cotton swabs. Written informed consent was obtained from all sample donors (18–47 years old) of the Chinese Han population living in the Sichuan Province. All samples were stored at 80 8C following collection. RNA isolation was performed on individual cotton swabs. Body fluid samples for TaqMan-qPCR validation (including those used for array screening) were collected from ten unrelated individuals. To observe the effect of natural environment on the miRNAs, cotton swabs were kept under normal laboratory conditions (approximately 15 8C and about 10-hour natural daylight exposure per day) for 1 month.