It takes only a few saliva cells on a licked stamp to catch a crook. Most cells in the human body contain DNA, the instruction book for building a specific person. By extracting DNA from samples of blood, semen, or other cells found at a crime scene, forensic scientists can tell if a suspect's DNA matches the cells left behind on evidence.

NIST helps the Federal Bureau of Investigation and other forensic laboratories ensure that their DNA tests are accurate. NIST prepares Standard Reference Materials that these laboratories use to check the accuracy of their DNA matching equipment and procedures.