citizen's arrest

citizen's arrest

an apprehending of a person by a member of the public. It is assumed in the UK that a private citizen (including a police constable) may arrest another without warrant if the citizen has witnessed the commission of a serious crime. Any force used must be reasonable (or in certain limited circumstances where there has been no unlawful conduct but there is a real threat of a breach of the peace interfering with the rights of another that would involve unreasonable violence).