U.S. flag

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

Principles of Forensic DNA for Officers of the Court


Home  |  Glossary  |  Resources  |  Help  |  Contact Us  |  Course Map


Photo of a woman bending down picking up a cigarette while holding her nose
National Institute of Justice (NIJ) (see reuse policy).

Contamination of DNA from one source can occur when it comes into contact with DNA from another source.

Contamination can occur during collection, such as handling the evidence without wearing gloves, failing to change gloves between collecting samples, or packaging two or more items in the same collection container.

Contamination may occur in the laboratory, such as when equipment is not properly cleaned before an item is examined.

Back Forward