The mere fact that a police constable had been instructed by a superior officer to arrest a person was not capable of amounting to "reasonable grounds for suspecting" that person of being involved in terrorism under the Prevention of Terrorism (Temporary Provisions) Act 1984. The constable must be given some basis for such an instruction, such as a report of an informer, from which he could reasonably form a genuine suspicion in his own mind.
The House of Lords dismissed an appeal by the plaintiff, Gerard O'Hara, against the decision of the Court of Appeal on 6 May 1994, affirming the decision of Mr Justice McCollum on 14 September 1990, dismissing the plaintiff's claim against the Chief Constable of the Royal Ulster Constabulary for damages for unlawful arrest and false imprisonment.
Section 12(1) of the 1984 Act (now section 14(1) of the Prevention of Terrorism (Temporary Provisions) Act 1989) provided that:
a constable may arrest without warrant a person whom he has reasonable grounds for suspecting to be . . . (b) a person who is or has been concerned in the commission, preparation or instigation of acts of terrorism . . .
The plaintiff was arrested on 28 December 1985 after a search had been conducted at his house at 72 Duncreggan Road, Londonderry. He was detained for questioning at Castlereagh Police Office before subsequently being released without charge.
At the trial of the plaintiff's action against the Chief Constable, the arresting officer, DC Stewart, said in evidence that he had attended a briefing at Strand Road Police Station at 5.30 am on the morning of 28 December 1985. The purpose of the briefing was to mount an operation to search houses to look for weapons or other evidence and to arrest a number of people in connection with a recent act of terrorism. The briefing was conducted by an inspector and was attended by a number of other officers.
The court held that the information given at the briefing was admissible and was sufficient to constitute the state of mind required of an arresting officer under section 12(1)(b).
Hugh Kennedy QC and Barry MacDonald BL (B.M. Birnberg & Co) for the plaintiff; Patrick Coghlin QC and Piers Grant BL (Treasury Solicitor) for the defendant.
Lord Hope said the test which section 12(1) laid down was a simple but practical one. It related entirely to what was in the mind of the arresting officer when the power was exercised. In part it was a subjective test, because he must have formed a genuine suspicion in his own mind that the person had been concerned in acts of terrorism.
In part it was also an objective one, because there must also be reasonable grounds for the suspicion. But the objective test did not require the court to look beyond what was in the mind of the arresting officer.
It was the grounds which were in his mind at the time which must be found to be reasonable grounds for the suspicion he had formed. All the objective test required was that these grounds be examined objectively and that they be judged at the time when the power was exercised.
The question was not whether the arresting officer himself thought at the time that they were reasonable, but whether a reasonable man would be of that opinion, having regard to the information which was in the mind of the arresting officer. It was the arresting officer's own account of the information which he had which mattered, not what was observed by or known to anyone else.
The information acted on by the arresting officer need not be based on his own observations, as he was entitled to form a suspicion based on what he had been told. His reasonable suspicion might be based on information which had been given to him anonymously or it might be based on information, perhaps in the course of an emergency, which turned out later to be wrong. As it was the information which was in his mind alone that was relevant, it was not necessary to prove that the information or facts on which his suspicion was based were true.