Crime Scene Preservation, Chain of Custody, and Evidence Handling
Domain 7 tests evidence handling from the moment a lock, key, or tool is identified until it is presented in court. The examiner must preserve condition, prevent contamination, and be able to account for every transfer.
Core rules
- Minimize handling. Wear gloves; handle by edges; avoid touching keyway, bolt face, or suspected tool marks.
- Package metal in breathable paper or suitable evidence containers; avoid sealed plastic when moisture or biological contamination is possible. Use tamper-evident seals and label with case number, item number, date, time, location, and collector.
- Create a custody log at seizure. Each entry records from whom, to whom, date, time, purpose, and seal condition. Never sign for an item you did not receive or transfer.
- Store in a secure, dry, access-controlled location. Separate items to prevent cross-transfer. Document any opening, examination, or repackaging.
- If disassembly is required, document and package components separately, then reseal with a new seal and note the old seal number.
Worked example
A padlock is collected from a wet door. You photograph it in place, blot surface water, place it in a paper bag, seal it, and write the seal number across the seal and bag. At the lab, you note the seal is intact, photograph it before opening, and log the opening. After examination, you repackage it with a new seal and record both seal numbers. The chain is unbroken.
Traps
- Sealing wet ferrous evidence in plastic and causing corrosion.
- Signing a custody entry without verifying the seal.
- Opening a package without documenting the seal number.
- Storing keys and suspect tools together, inviting cross-transfer.
- Relying on memory instead of contemporaneous notes.