Key Cases on Wrongful Arrest

An arrest is unlawful if the officer does not have reasonable grounds for suspicion, if the necessity criteria under section 24(5) of PACE are not met, or if the officer fails to inform the person of the grounds for arrest. A person who is unlawfully arrested may bring a civil claim for false imprisonment against the chief constable.

Christie v Leachinsky [1947] AC 573 (House of Lords) established the foundational principle that a person must be told the reason for their arrest at the time of arrest, or as soon as is practicable thereafter. Lord Simonds stated: "a person is entitled to know the ground on which he is being arrested." Failure to inform the person renders the arrest unlawful from its inception.

Richardson v Chief Constable of West Midlands [2011] EWHC 773 concerned the necessity criteria for arrest under PACE s.24(5). The court held that the officer must genuinely consider whether arrest is necessary and must be able to identify which of the statutory necessity criteria applied. A "blanket" arrest based on convenience, without turning the mind to whether each individual's arrest was necessary, is unlawful.

Castorina v Chief Constable of Surrey (1988) 138 NLJ 180 (Court of Appeal) addressed the question of reasonable grounds for suspicion. The court held that the officer must have subjective suspicion and that suspicion must be objectively reasonable: a genuine but wholly unreasonable suspicion is insufficient. However, the test is not whether there is a prima facie case: suspicion is a lower threshold than belief or proof.

The consequences of an unlawful arrest include: the person must be released immediately once the illegality is recognised; any detention following an unlawful arrest is also unlawful (false imprisonment); evidence obtained as a result of the unlawful arrest may be excluded under section 78 of PACE; and the person may bring a civil claim for damages. Damages for false imprisonment are awarded by reference to the duration of the detention and the circumstances, following the guideline bands in Thompson v Commissioner of Police [1998] QB 498.