Arrest is the act of lawfully depriving a person of their liberty so they are no longer free to leave, typically as a step in the criminal process. Across England and Wales, Scotland, Northern Ireland and Ireland, an arrest usually involves informing the person that they are under arrest and the grounds for it, and taking them into custody for questioning, charge or court appearance. In England and Wales and Northern Ireland, the core powers and safeguards are set out in the Police and Criminal Evidence Act 1984 (PACE) and corresponding Northern Irish legislation, alongside specific statutory powers (for example, terrorism, immigration). In Scotland, arrest is governed by the Criminal Justice (Scotland) Act 2016, which codifies when and how police may arrest without warrant. In Ireland, arrest powers derive from common law and multiple statutes, including the Criminal Justice Act 1984. Key legal issues include reasonable suspicion, necessity (where applicable), use of reasonable force, and compliance with rights to information, access to legal advice and prompt court review. An unlawful arrest may found civil claims (false imprisonment, assault), exclusion of evidence, or challenges to prosecution.