1. 12.6 Notes
Semen & Rape

2. Objectives
List the laboratory tests necessary to characterize seminal stains
Explain how suspect blood and semen stains are properly preserved for laboratory examination
Describe the proper collection of physical evidence in a rape investigation.

3. Characterization of Semen
Normal male releases 2.5 to 6-mL during ejaculation
Each mililiter contains 100 million+ spermatozoa
Sperm are indicative of semen
Oligospermia – low sperm count
Aspermia – no sperm in seminal fluid

4. Forensic examination for seminal stain
2 step process
Stain must be located usually using an acid phosphatase color test
Acid phosphatase = enzyme secreted by the prostate gland into seminal fluid
Concentrations are up to 400x greater than in other bodily fluid
Turns purple when reacted with acidic solutions
Fluoresces under UV light with 4-methyl umbelliferyl phosphate (MUP)
Subject to test to prove its identity

5. Semen
Protein p30 or prostate specific antigen (PSA) is a protein unique to seminal plasma
Stimulates the production of polyclonals when injected into a rabbit
Currently a new technique is used that places a monoclonal PSA antibody on a porous membrane which then moves toward a polyclonal PSA also on the same membrane

6. Rape Evidence
Seminal constituents on a rape victim are important evidence that sexual intercourse took place
Their absence does not necessarily mean that a rape did not occur
Physical injuries such as bruises and bleeding tend to confirm that a violent assault occurred
Forceful physical contact between victim and assailant may results in the transfer of physical evidence – blood, semen, hairs, fibers

7. Collection of Rape Evidence
To protect the evidence, all outer garments and undergarments of the persons involved are carefully removed and packaged separately in paper bags
A clean bed sheet and clean paper sheet are placed on the floor and the victim removes all their clothing
Paper collects any loose foreign material falling from the clothing
Each piece of clothing is individually bagged to avoid cross-contamination
Paper is carefully folded to keep all foreign material inside

8. Collection of Rape Evidence CONT….
Items suspected of containing seminal stains are carefully handled
Folding the article can cause the stain to flake off
Rubbing against the surface of the packaging material can also cause flaking
Analysts try to link seminal material to donor(s) using DNA typing
Individuals may transfer their DNA types to a stain through perspiration, so special care must be taken to minimize direct personal contact with the stain

9. Collection of Rape Evidence CONT….
Rape victim undergoes a complete medical examination as soon as possible following the assault
Physical evidence is collected by trained personnel
It includes: pubic combings, pubic hair standard/reference sample, external and internal genital skin area swabs (vaginal, cervical, rectal, oral), head hairs, blood sample, fingernail scrapings, all clothing, urine specimen.

10. Collection of Rape Evidence CONT….
From the suspect, physical evidence is also collected.
It includes: all clothing, pubic hair combs, pulled head and pubic hair standard/reference samples, penile swab, and blood sample or buccal swab for DNA

11. 12.6 Questions
What test is used to locate and characterize seminal tissue? Why is it useful?
Differentiate between oligospermia and aspermia
What protein is indicative of semen and what two tests are used to detect this protein?
Why must a rape victim stand on a sheet of paper while disrobing for forensics analysis?
Besides swabbing for semen constituents, what other bodily fluids should be collected from a rape victim during a medical examination?
What items should be collected from the suspected perpetrator of sexual assault? (at least 4 things)
How long do motile sperm generally survive in the vaginal cavity of a living female?
How long do non-motile sperm generally survive in the vaginal cavity of a living female?