Forensic Characterization of Semen The presence of seminal stains is important in crimes involving sexual offenses. The presence of seminal stains is important in crimes involving sexual offenses. Two steps: 1. Stains must be located 2. Stains are tested to determine identity

Testing for Seminal Stains Stains can sometimes be identified visually. Stains can sometimes be identified visually. Acid phospatase test- Acid phosphatase is an enzyme found in large concentrations in semen. Acid phospatase test- Acid phosphatase is an enzyme found in large concentrations in semen. 2 tests: 1. Acid phophatase reacts with sodium alpha naphthylphospate and Fast Blue B dye to give a purple color. 2. Acid phospatase reacts with 4-methyl umbelliferyl phosphate, which fluoresces under UV light

Testing for Seminal Stains Microscopic Examination- Semen can be identified by the presence of spermatozoa Microscopic Examination- Semen can be identified by the presence of spermatozoa Prostate Specific Antigen – antigen/antibody reaction confirms the presence of seminal fluid Prostate Specific Antigen – antigen/antibody reaction confirms the presence of seminal fluid

Collection of Rape Evidence Evidence of rape is not limited to semen Physical injuries Physical injuries Blood Blood Hairs Hairs fibers fibers

Collection of Rape Evidence Physical evidence collected from a rape victim include: Pubic combings Pubic combings Pubic hair reference samples Pubic hair reference samples External genital dry- skin samples External genital dry- skin samples Vaginal swabs Vaginal swabs Cervix swabs Cervix swabs Rectal swabs Oral swabs Head hairs Blood sample Fingernail Scrapings Clothing Urine specimen

Collection of Rape Evidence If a suspect is apprehended, the following physical evidence would be collected. Clothing Clothing Pubic hair combings Pubic hair combings Head and pubic hair samples Head and pubic hair samples A penile swab A penile swab Blood sample or buccal swab Blood sample or buccal swab