Detailed Procedure:

Semen is typically found on a substrate, most often an item of clothing, bedding, towels, tissues, or floor covering.

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To collect an item with a questioned semen stain:

1. Semen is a bodily fluid. When collecting, observe Universal Precautions. Wear new, unused, clean latex or nitrile gloves. Wear respiratory and eye protection as needed.

2. Photograph the semen-stained item in place.

3. If the semen stain is wet, place the item on new, clean, dry paper. Place the item and paper in a draft-free, dry location that is secure, ensuring no one will touch, step on, remove, or displace the item. Allow the item to air dry. Do not package the item when wet; it may putrefy and therefore lose its evidentiary value.

4. When the item is dry, package it in an appropriately sized, air-permeable but closed container, such as a cardboard box, paper envelope, or paper bag. Prior to inserting the item, label the container with identifying information, including case number, date, exhibit number, a brief description, and your name. Do not fold the item unless it is absolutely necessary. If the item must be folded, protect the stained area with a piece of paper and avoid folding across the stained area.

5. If the semen is on an immovable surface, like a tile floor, it can be collected using an absorbent medium, such as a new, clean, sterile cotton gauze pad.

   1. Open the gauze pad packaging and lay the pad on the semen stain. Allow the pad time to absorb the semen. If the pool is not sufficient for absorption onto a sterile cotton gauze pad, collect the stain using a sterile swab, rubbing it over the stain to remove as much of the semen as possible. Be sure to concentrate as much semen as possible on each swab (ie: two swabs with concentrated amounts of semen are better than six swabs slightly stained with semen).

   2. Air dry the gauze pad or swab before packaging by laying it on a clean sheet of paper or hanging it up, at room temperature, away from direct heat, sunlight, or drafts. If semen evidence items are not dried before packaging, they may putrefy and therefore be unusable.

   3. Label a new, clean, evidence collection envelope with identifying information, including case number, date, exhibit number, a brief description, and your name.

   4. Once the gauze pad or swabs are dry, place them into the prepared envelope. If swabs are submitted, place them cotton tip first into the envelope.

   5. Submit a new, unused gauze pad or swab in a separate container as a control sample.

6. Seal the container(s) with evidence tape, not your own saliva. Initial and date the tape.

7. Store the item in a secure, temperature-controlled location, such as a refrigerator or climate-controlled evidence storage room, until you are able to transport it to the laboratory. Do not leave the swabs or any biological evidence in a hot car.

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If you are unsure how to collect semen or a semen-stained item, document the item photographically and contact your forensic laboratory for guidance before proceeding with collection procedures. If the semen-stained item will also be examined for ignitable liquid residue, please consult the laboratory for the proper collection procedure. Items should not be air-dried or packaged in an air-permeable container if they will be examined for ignitable liquid residue.

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Laboratory testing of semen:

Semen samples can be examined to determine nuclear DNA profile (sex is determined during the DNA analysis). Comparison of a questioned nuclear DNA profile to known profiles is possible. For some types of analysis, comparison to other samples via computerized database (eg: CODIS for DNA profiles) is possible.

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Known DNA samples:

Generally, known DNA is collected using a buccal swab. Please contact your forensic laboratory for assistance. A court order may be required to collect this type of sample.

 

Source:

Crime Scene and Evidence Collection Handbook. Bureau of Alcohol, Tobacco, Firearms and Explosives, 2005.