S & Anor, R v

A compulsory requirement to disclose knowledge of an encryption key may engage the privilege against self-incrimination where that knowledge tends to incriminate its holder. The encrypted data and key are nevertheless facts existing independently of the holder’s will, and the key does not itself amount to an admission of guilt.

A limited statutory qualification of the privilege is compatible with article 6 where it pursues the legitimate objectives of national security or crime prevention and detection, is proportionate, is subject to judicial oversight, and concerns data lawfully held by the authorities. The continuing power to exclude unfairly obtained evidence protects the overall fairness of any later trial.

S and A were charged with conspiring to breach a control order. Computer material seized by the police included encrypted files which could not be accessed without encryption keys known, it was alleged, to the appellants.

Notices served under Part III of the Regulation of Investigatory Powers Act 2000 required each appellant to disclose the relevant key or information sufficient to make the data intelligible. Neither complied, and each faced counts under section 53.

At a preparatory hearing in the Central Criminal Court, Judge Martin Stephens QC refused to stay those counts. The appellants brought interlocutory appeals, contending that compelled disclosure infringed the privilege against self-incrimination and article 6 of the European Convention of Human Rights.

Appeals dismissed.

1. The court held that the judge had been wrong, if he treated an appellant’s knowledge of the means of access as identical to the encryption key itself. A compelled requirement to convey that knowledge may engage the privilege against self-incrimination, because knowledge of the key may support an inference that the appellant knowingly possessed incriminating material.

2. That conclusion did not make the notices unlawful or unfair. The encrypted data, and the key as a fact, existed independently of the appellants’ wills. The notices required no admission about the contents. They required only enough information to make lawfully obtained data intelligible.

3. Any interference with the privilege was very limited and proportionate. Under section 49 of the Regulation of Investigatory Powers Act 2000, a notice required judicial permission and depended on lawful acquisition, necessity, proportionality, and the absence of a reasonably practicable alternative means of access. Its objectives of national security and prevention or detection of crime were legitimate. The limited disclosure requirement did not compromise the overall fairness required by article 6.

4. The trial judge retained the power under section 78 of the Police and Criminal Evidence Act 1984 to exclude the underlying material, the key, or evidence of knowledge of it if the circumstances of acquisition rendered a later trial unfair. Accordingly, there was no basis to interfere with Judge Stephens’ discretionary indication and no possible basis to stay the section 53 prosecutions as an abuse of process.

• Court of Appeal (Criminal Division): In [2008] EWCA Crim 2177, the court dismissed the interlocutory appeals against the refusal to stay the section 53 counts.
• Central Criminal Court: During a preparatory hearing on 26 June 2008, Judge Martin Stephens QC refused the appellants’ applications to stay the counts alleging offences under section 53 of the Regulation of Investigatory Powers Act 2000.