Powers of Arrest: A Practical Guide

An arrest is the act of depriving a person of their liberty for the purpose of taking them before a court, bringing them before a constable, or otherwise dealing with them under a statutory power. In England and Wales, the primary power of arrest for constables is found in section 24 of PACE 1984. A constable may arrest without a warrant anyone who is about to commit an offence, is in the act of committing an offence, or whom the constable has reasonable grounds for suspecting to be committing or to have committed an offence.

Crucially, the power to arrest is not automatic merely because the first limb is satisfied. Under section 24(4) and (5) of PACE, the constable must also have reasonable grounds for believing that arrest is necessary. The necessity criteria set out in Code G include: to ascertain the person's name or address; to prevent the person causing physical injury, suffering injury, causing loss or damage, committing a public decency offence, or obstructing the highway; to protect a child or vulnerable person; to allow prompt and effective investigation; or to prevent prosecution being hindered by the person's disappearance. If none of the necessity criteria applies, an arrest is unlawful even if there are grounds for suspecting an offence.

Private citizens also retain a power of arrest under section 24A of PACE, which was inserted by the Serious Organised Crime and Police Act 2005. A person other than a constable may arrest without a warrant someone who is in the act of committing an indictable offence, or whom the person has reasonable grounds for suspecting to be committing an indictable offence. The citizen must also believe that it is not reasonably practicable for a constable to make the arrest instead. This power is narrower than the constable's power and applies only to indictable offences.

When making an arrest, the constable must inform the person that they are under arrest and the ground for the arrest, even if this is obvious from the circumstances: Christie v Leachinsky [1947] AC 573. The person must also be cautioned. Failure to comply with these requirements may render the arrest unlawful, with consequences for any subsequent prosecution.