U.S. flag

An official website of the United States government, Department of Justice.

Collecting DNA Evidence at Property Crime Scenes

Collecting a Sample from a Smear

Collecting a Sample from a Smear

Collecting a sample from a smear is different from collecting from a thicker stain. Use the following procedure:

  • Use a slightly moistened (with distilled water), sterile cotton swab and concentrate the substance on the tip of the swab.
  • Collect a control sample by swabbing unstained adjacent surface areas with a sterile swab slightly moistened with distilled water.
  • Use a slightly moistened swab and follow with a second dry swab for a perspiration smear.
  • Allow the swabs to air-dry.
  • Label and package evidentiary swabs and control swabs separately in envelopes or bindle paper.

Back Forward