Forensic Characterization of Semen

1
Forensic Characterization of Semen

• The presence of seminal stains is important in
  crimes involving sexual offenses.
• Two steps
• Stains must be located
• Stains are tested to determine identity

2
Testing for Seminal Stains

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

3
Testing for Seminal Stains

• Microscopic Examination- Semen can be identified
  by the presence of spermatozoa
• Prostate Specific Antigen antigen/antibody
  reaction confirms the presence of seminal fluid

4
Collection of Rape Evidence

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

5
Collection of Rape Evidence

• Physical evidence collected from a rape victim
  include
• Pubic combings
• Pubic hair reference samples
• External genital dry-skin samples
• Vaginal swabs
• Cervix swabs

• Rectal swabs
• Oral swabs
• Head hairs
• Blood sample
• Fingernail Scrapings
• Clothing
• Urine specimen

6
Collection of Rape Evidence

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