Albert v Lavin

Factual and Procedural Background

The Respondent, an off-duty police constable in plain clothes, was standing at the head of a queue at a bus stop in The City. The Appellant attempted to jump the queue. The Respondent, believing a breach of the peace to be imminent, physically restrained the Appellant to prevent him from boarding the bus out of turn. During the restraint the Respondent announced that he was a constable. The magistrates later found that the Appellant, though in an excited state, honestly but unreasonably disbelieved this assertion and struck the Respondent five or six times in the stomach.

The Appellant was subsequently arrested and convicted in The Magistrates’ Court for assaulting a constable in the execution of his duty, contrary to section 51 of the Police Act 1964. He appealed by way of case stated to the Divisional Court, which dismissed the appeal. A further appeal was brought to the House of Lords (now “the Court”) where the present opinion was delivered.

Legal Issues Presented

1. Whether a constable who reasonably believes that a breach of the peace is about to occur may lawfully detain a person without formal arrest to prevent that breach.
2. Whether a person so detained, who does not accept that the detainer is a constable, can be convicted of assaulting a constable in the execution of his duty when he uses only such force as he reasonably believes necessary to defend himself against what he mistakenly believes to be an unlawful assault and false imprisonment.

Arguments of the Parties

The opinion does not contain a detailed account of the parties' legal arguments.

Table of Precedents Cited

No precedents were cited in the provided opinion.

Court's Reasoning and Analysis

Judge Diplock, delivering the principal speech, observed that the Divisional Court had proceeded on an erroneous assumption that detention without arrest is always unlawful save for one exception relating to constables. The Court identified an “equally well-established” common-law exception applicable to all citizens: any individual who witnesses a breach of the peace, or reasonably apprehends one, has both the right and (subject to imperfect obligation) the duty to take reasonable steps— including detention— to prevent or terminate the disturbance.

Applying this principle, the magistrates’ factual findings established that a breach of the peace was imminent and that the Respondent’s restraint of the Appellant fell within the scope of reasonable preventive action. Consequently, even if the Respondent had been a private citizen rather than a constable, his conduct would have been lawful. The Appellant’s forceful resistance therefore constituted an unlawful assault.

The Court further noted that the Divisional Court’s extended discussion of mens rea and the reasonableness of mistaken belief was irrelevant. The certified question—whether an accused may be convicted of assault where he acts under an unreasonable but honest mistake of fact—is hypothetical in the circumstances and need not be answered.

Holding and Implications

Appeal dismissed. The conviction for assaulting a constable in the execution of his duty stands.

Implications: The decision reaffirms the common-law right (and corresponding duty) of any citizen to take reasonable steps, including detention, to prevent a breach of the peace. It clarifies that an assailant cannot rely on an honest but unreasonable belief about the status of the person restraining him when the restraint itself is otherwise lawful under this common-law principle. No new legal precedent is created; the ruling restates existing doctrine and corrects the misapprehension articulated by the lower court.