ABSTRACT
In O’Hara v Chief Constable, Royal Ulster Constabulary [1997] 2 WLR 1; [1997] 1 All ER 129, the House of Lords considered the meaning of ‘reasonable grounds’ in the context of s 12(1)(b) of the Prevention of Terrorism (Temporary Provisions) Act 1984 (now s 14(1) of the Prevention of Terrorism (Temporary Provisions) Act 1989), which applies the same test as s 24 of the Police and Criminal Evidence Act 1984. It was held that, for a police officer to have reasonable grounds to effect an arrest, the question is whether a reasonable person would be of that opinion, having regard to the information which was in the mind of the arresting officer. In other words, the test is partly subjective (the officer must have formed a genuine suspicion in his own mind that the suspect has committed the offence in question) and partly objective (there must be reasonable grounds for that suspicion). The House of Lords went on to hold that the information acted on by the officer need not be based on his own observations: he is entitled to form a suspicion on the basis of what he has been told. It is not necessary to prove what was known to the person who gave the information to the police officer or to prove that any facts on which the officer based his suspicion were actually true.
