Fire Scene Evidence Collection Guide

Bodily Fluids

Bloodstain on Substrate

Detailed Procedure:

Any investigator working at a scene where blood or bodily fluids may be present should observe Universal Precautions. Please consult your laboratory for specific guidance on how to collect blood evidence based on the particular situation and the scene you are processing.

To collect bloodstains from substrates:

  1. Photograph the bloodstain and the item bearing the bloodstain. Photograph spatters, stains, and drops in both wide angle and closeup.

  2. Wear new, unused, clean latex or nitrile gloves, respiratory protection, and eye protection.

  3. Collect the entire item bearing the bloodstain, if possible. Use a tool appropriate to the item, taking care not to touch, smear, or alter the bloodstain. If the full item cannot be collected, dismantle it (if possible) so you can collect only the portion bearing the bloodstain. For example, remove the cushion from a chair or cut away part of a large piece of fabric or carpet. If the stain and/or substrate is wet, air dry it before packaging by laying it on a clean sheet of paper, at room temperature, away from direct heat, sunlight, and drafts. If blood evidence items are not dried before packaging, they may putrefy and therefore be unusable.

  4. Label an air-permeable container with identifying information, including case number, date, exhibit number, a brief description, and your name.

  5. Place the item inside the container.

  6. If it is not possible to collect the item or the portion of the item bearing the bloodstain, such as a bloodstain on a tile floor or a bathroom fixture, you may swab the item.

    1. If the bloodstain is wet, open a new, unused, clean sterile cotton swab and rub the swab over the stain. If the bloodstain is dry, open a new, unused, clean sterile cotton swab. Moisten the swab in distilled or sterile water. Then, rub the moistened swab over the stain to remove as much of the blood as possible. Be sure to concentrate as much blood as possible on each swab (ie: two swabs with concentrated amounts of blood are better than six swabs slightly stained with blood).

    2. Air dry the swab in a position where the swabbed end does not have contact with any surface. Do not touch the cotton end of the swab.

    3. Label an air-permeable container with identifying information, including case number, date, exhibit number, a brief description, and your name.

    4. Once the sample is dry, place it into an air-permeable container and then place that container into a new, clean evidence collection envelope. If swabs are being submitted, place them cotton tip first into the envelope.

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

  7. Seal the envelope and/or container with tape, not your saliva. Initial and date the tape.

  8. 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.

If you are unsure how to collect a bloodstained item, document the item photographically and contact your forensic laboratory for guidance before proceeding with collection procedures. If the bloodstained 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.

Laboratory testing of blood:

Blood samples can be examined to possibly determine the nuclear DNA profile (sex is determined during the DNA analysis), species, blood type, and other characteristics of the donor. Comparison of questioned nuclear DNA profiles to known profiles is possible. Comparison of DNA to other samples via computerized database (eg: CODIS for DNA profiles) may be possible.

Known blood 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:

CFITrainer.Net®. “Evidence Collection Toolbox.” Website, video, 2013.

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