Forensic Biology by Richard Li Chapter 8: Identification of Semen Forensic Biology by Richard Li

Biological Characteristics Typical ejaculation 2-5 ml of semen Seminal fluid Seminal vesicle fluid- 60% of ejaculate Prostatic fluid secretions- 30% of ejaculate Acid Phospahatase (AP) & Prostate Specific Antigen (PSA) Epididymis and bulbourethral glands- each 5% Sperm cells- Spermatozoa Forensic Biology by Richard Li

Biological Characteristics Vasectomy- block spermatozoa Still produces ejaculate with seminal vesicle fluid and prostatic fluid Oligospermia- low sperm count Aspermia- no sperm Forensic Biology by Richard Li

Spermatozoa Three distinct regions: Head Middle Piece Tail Forensic Biology by Richard Li

Acid Phosphatase Optimal activity in acidic pH environment Present in lysosomes Prostate AP Half-life at 37 degrees C: 6 months Forensic Biology by Richard Li

Prostate-Specific Antigen Major protein in seminal fluid Also detected in urine, fecal matter, sweat, milk Half-life of dried stain: 3 years Forensic Biology by Richard Li

Seminal Vesicle Specific Antigen Semenogelins I & II Higher concentration in seminal fluid than PSA Not found in urine, milk, sweat Forensic Biology by Richard Li

Lighting Techniques Locating dried stains UV light Argon laser Alternate light source (ALS) 450-495 nm Forensic Biology by Richard Li

Colorimetric Assay AP catalyzes the removal of the phosphate group from a substrate Positive= purple color Forensic Biology by Richard Li

Fluororimetric Assay More sensitive than colorimetric AP catalyzes the removal of the phosphate residue on the substrate 4-methylumbelliferone phosphate which generates fluorescence under UV light Forensic Biology by Richard Li

Confirmatory Tests Microscopic examination Christmas Tree Stain Laser capture microdissection Identification of prostate-specific antigen Radial immunodiffusion Rocket immunoelectrophoresis CIE ELISA Imunnochromatographic assays Most sensitive Forensic Biology by Richard Li