Investigative Techniques, Evidence Handling, and Surveillance
Planning and lawful method
This domain tests investigation planning, interviews, surveillance, and evidence integrity. Start with a written objective, the legal basis for each method, and a least-intrusive plan. Surveillance should be conducted from lawful public vantage points; trespass, peeping, stalking, and unlawful audio capture are not acceptable techniques. Record date, time, location, weather, identity of observer, and continuity of observation. For interviews, obtain voluntary participation, identify yourself, and document questions, answers, and any refusal.
Evidence handling
- Photograph and describe an item before moving it when practicable.
- Package, seal, label, and log each item; use a chain-of-custody form with every transfer.
- For digital evidence, preserve the original file, record a hash value, work from a copy, and document metadata.
- Keep contemporaneous notes; do not rewrite them later to fit a theory.
Worked example
A client provides parking-lot video showing a subject. The investigator copies the file without editing, records the source device and time, computes a hash, stores the original as evidence, and uses a working copy for review. Each transfer is logged. If the client later asks for a “clean” clip, the investigator supplies a derivative copy labeled as such and keeps the original intact. The reasoning is that authentication depends on continuity and integrity, not on a persuasive edit.
Traps
Frequent errors are editing the only copy, gaps in the chain-of-custody log, narrating surveillance from memory, and recording audio without all-party consent. Another trap is claiming continuous surveillance when there were breaks; note gaps honestly. Evidence that cannot be authenticated is weak even if it appears convincing.