Documentation, Chain of Custody, and Evidence Handling
Domain 7: Documentation, Chain of Custody, and Evidence Handling
This domain tests whether your data would survive a challenge. Good measurements can be rejected if the record is incomplete, altered, or disconnected from the instrument that produced it.
Core rules
- Record the who, what, when, where, and why: observer, instrument make/model/serial number, calibration dates and results, settings, weather, source operation, site map, GPS coordinates, and photographs.
- Maintain chain of custody from collection to storage. Each transfer should record date, time, handler, purpose, and signature.
- Preserve original raw files. Work on copies, and use checksums or hash values to demonstrate that files have not changed. Keep an audit trail of edits.
- Retain calibration certificates, field notes, and metadata for the period required by the contract or regulation.
- Document deviations and problems, including calibration drift, equipment failure, and access limitations.
Worked example
A data logger produced a valid one-hour file, but the after-calibration record is missing. The file may still be relevant, but its evidential weight is reduced because the instrument's post-deployment accuracy is unverified. If the chain-of-custody form also has an unexplained gap, opposing counsel can challenge authenticity. The fix is to document the gap honestly, not to reconstruct a record after the fact.
Traps
Editing raw data; overwriting files; missing calibration records; unsynchronized clocks; and treating photographs without metadata as sufficient documentation.