ACPO Digital Evidence Principles Explained
The four ACPO principles in plain English — what they mean for daily practice, and how Faraday isolation sits inside them.
Quick Answer
The four ACPO principles require that data is unchanged, examiners are competent, an audit trail is maintained, and the case officer is accountable. Faraday isolation operationalises Principle 1 from the moment of seizure.
Principle 1: No Action Should Change Data
Anything the seizing officer does that touches the device must not alter data. Network connectivity is the largest source of unintended change — Faraday isolation removes it.
Principle 2: Competence
Officers handling devices must be competent for the actions they take. Field isolation and sealing is in scope; advanced extraction is not — escalate to the DFU.
Principle 3: Audit Trail
Every action, decision and handover is logged. Bag serial, seal events, transport custody and examination steps form a continuous chain.
Principle 4: Officer-in-Charge Responsibility
The officer in the case retains ultimate responsibility for the integrity of the digital evidence. Process, training and kit must support — never undermine — that responsibility.
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