Semen & Rape

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.

Normal male releases 2.5 to 6-mL during ejaculationEach mililiter contains 100 million+

spermatozoa

Sperm are indicative of semenOligospermia – low sperm countAspermia – no sperm in seminal

fluid

2 step process Stain must be located usually using

an acid phosphatase color testAcid phosphatase = enzyme secreted by

the prostate gland into seminal fluidConcentrations are up to 400x greater

than in other bodily fluidTurns purple when reacted with acidic

solutionsFluoresces under UV light with 4-methyl

umbelliferyl phosphate (MUP) Subject to test to prove its identity

Protein p30 or prostate specific antigen (PSA) is a protein unique to seminal plasmaStimulates the production of polyclonals

when injected into a rabbitCurrently 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

Seminal constituents on a rape victim are important evidence that sexual intercourse took placeTheir 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

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 clothingPaper collects any loose foreign material

falling from the clothingEach piece of clothing is individually bagged

to avoid cross-contaminationPaper is carefully folded to keep all foreign

material inside

Items suspected of containing seminal stains are carefully handledFolding the article can cause the stain to

flake offRubbing 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

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.

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

1. What test is used to locate and characterize seminal tissue? Why is it useful?

2. Differentiate between oligospermia and aspermia

3. What protein is indicative of semen and what two tests are used to detect this protein?

4. Why must a rape victim stand on a sheet of paper while disrobing for forensics analysis?

5. Besides swabbing for semen constituents, what other bodily fluids should be collected from a rape victim during a medical examination?

6. What items should be collected from the suspected perpetrator of sexual assault? (at least 4 things)

7. How long do motile sperm generally survive in the vaginal cavity of a living female?

8. How long do non-motile sperm generally survive in the vaginal cavity of a living female?