- 1: Types of Evidence
- 2: Types of Crime Scenes
- 3: Evidence Collection
- Collection Priority
- Control Samples
- Reference Sample Collection
- Equipment
- Procedures
- Biological Evidence Packaging
- Blood and Body Fluid Collection
- Hair and Fiber
- Wet Stains on Absorbent Surfaces
- Special Situations
- Wet Stains on Nonabsorbent Surfaces
- Dry Stains on Absorbent Surfaces
- Dry Stains on Nonabsorbent Surfaces
- Collecting a Sample From a Smear
- Evidence Marking
- Packaging for Transport
- Chain of Custody
- Preserving Evidence
- Reporting
- Testifying
- Summary
- 04: CODIS
Dry Stains on Nonabsorbent Surfaces
Home > 3. Evidence Collection > Dry Stains on Nonabsorbent Surfaces
Collection procedures for dry stains on nonabsorbent surfaces are as follows:
- Submit the entire item, if possible. (Note: If the entire item is submitted
and it is a sharp object such as broken glass, it will need to be safely
packaged in cardboard and labeled "sharp object enclosed.")
- Use a new or clean scalpel blade to scrape the stains from the surface.
- Collect the flakes onto clean paper and fold the paper in a bindle.
- If the stain is on wood, shave the area of the bloodstain with a new or
clean scalpel blade.
- Package each item separately.
- Place sample in a labeled envelope that provides reference information
on where the sample was collected.
- Take a control swabbing from unstained areas using a new sterile swab slightly
moistened with distilled water. Allow the control swab to air-dry, label
and package in paper.
- If determined by your agency protocol, collect the sample with tape using the following procedure:
- Place fingerprint tape (do not touch sticky surface with bare hands) over bloodstain and surrounding negative control area.
- Rub nonsticky side of tape with a pencil eraser or other blunt object. This is to ensure that good contact is made between the stain and the tape.
- Lift the bloodstain like a fingerprint and place the tape on an acetate backing. (Do NOT use a paper backing — paper makes the stain difficult to handle during analysis). The lifting process can be repeated several times on the same stain if necessary.
- Label the stain(s) and package individually in a paper envelope.
Advantages:
The dilution and contamination potential is minimized by eliminating the use of water as the collection medium; a control is readily collected; it requires little storage space and is a fairly easy technique to perform.
Disadvantages:
Investigator must decide which stains to collect; bloodstains do not lift well off certain surfaces. A potential drawback to this method is possible touch DNA contamination if the investigator repeatedly reaches into a common tape lift bag or handles the sample using nonclean techniques.
