An arrest is lawful only if two separate conditions were met at the moment it happened. Officers frequently satisfy the first and not the second, and the second is where most wrongful arrest claims are won.
What the law requires
Section 24 of the Police and Criminal Evidence Act 1984 gives a constable power to arrest without a warrant, but only where two things are true at once. First, the officer must have reasonable grounds to suspect that an offence has been, is being, or is about to be committed. Second, under section 24(4), the officer must have reasonable grounds for believing that arrest is necessary for one of the reasons listed in section 24(5), such as allowing a prompt and effective investigation, preventing injury, or stopping the person disappearing.
"But the power of summary arrest conferred by subsection (1), (2) or (3) is exercisable only if the constable has reasonable grounds for believing that for any of the reasons mentioned in subsection (5) it is necessary to arrest the person in question."
Police and Criminal Evidence Act 1984, section 24(4)The word doing the work there is only. The necessity test is not a factor to weigh alongside suspicion. It is a condition without which the power does not exist.
Suspicion alone is not enough. An officer who genuinely and reasonably suspects an offence, but who cannot explain why arrest rather than a voluntary interview was necessary, has made an unlawful arrest.
What has to be shown
A wrongful arrest claim is a claim in trespass to the person. It is actionable per se, which means you do not have to prove you suffered a loss: the unlawful detention is itself the wrong. In practice the argument turns on:
- whether the officer actually held the suspicion, and whether it was objectively reasonable
- whether the necessity test in section 24(5) was addressed at all
- whether the reason given at the time matches the reason relied on afterwards
The burden sits with the police. Once you show you were arrested, it is for the force to prove the arrest was lawful, not for you to prove it was not.
How long you have to bring a claim
Publishing a general figure here would be worse than publishing nothing, because a reader who relies on the wrong one loses their claim outright. Get your own position checked, and do it early rather than late.
The free routes, before any claim
A complaint to the force costs nothing and does not stop you claiming later. If the force's answer does not stand up you can apply for a review, and across all forces reporting, 24.5% of completed reviews found the force's own outcome was not reasonable and proportionate.
The three routes, and what each one gets you.
Start with your force
Complaint handling, review outcomes and stop and search practice vary enormously between forces. Every force has its own page here with its own figures.