Short answer: Chain of custody is the written record of who collected a specimen, who handled it, and when. It is what makes a legal DNA or drug test defensible.

• What we record: identity checks, the collection, tamper-evident sealing, and every transfer until the laboratory receives the specimen.
• Legal vs non-legal: legal DNA tests use chain of custody; non-legal tests and home kits do not.
• Drug tests: chain of custody applies to laboratory drug tests too, using a custody and control form.