The House of Lords (Lord Slynn and Lord Lloyd dissenting) reversed the decision of the Divisional Court (Law Report, 30 October 1998), which had quashed provisional warrants issued under section 8(1)(b) of the Extradition Act 1989 at the request of the Spanish Government for the arrest of the applicant.
The charges against the applicant were torture, contrary to section 134(1) of the Criminal Justice Act 1988, and hostage-taking, contrary to section 1 of the Taking of Hostages Act 1982. It was conceded that both offences were extradition crimes within the meaning of the Extradition Act.
The Divisional Court quashed the warrant on the ground that the applicant was head of the Chilean state at the time of the alleged offences and that he was, therefore, entitled to immunity from the criminal processes of the English courts. The court certified, as a question of law of general public importance, "the proper interpretation and scope of the immunity enjoyed by a former head of state from arrest and extradition proceedings in the United Kingdom in respect of acts committed while he was head of state".
Alun Jones QC, Professor Christopher Greenwood, James Lewis and Campaspe Lloyd-Jacob (Crown Prosecution Service, International Division) for the Government of Spain and the Metropolitan Police; Clive Nicholls QC, Clare Montgomery QC, Helen Malcolm, James Cameron and Julian Knowles (Kingsley Napley) for the applicant; David Lloyd Jones (Treasury Solicitor) as amicus curiae; Professor Ian Brownlie QC, Michael Fordham, Owen Davies and Frances Webber (Bindmans) for Amnesty as intervenor.
Lord Nicholls said that section 20 of the State Immunity Act 1978 conferred personal immunity upon a head of state by reference "with necessary modifications" to the privileges and immunites enjoyed by the head of a diplomatic mission under the Vienna Convention on Diplomatic Relations 1961, which was enacted as a schedule to the Diplomatic Privileges Act 1964.
Those immunities included, under article 31, "immunity from the criminal jurisdiction of the receiving state". Accordingly there could be no doubt that if the applicant had still been head of the Chilean state, he would have been entitled to immunity.
Whether he continued to enjoy immunity after ceasing to be head of state turned upon the proper interpretation of article 39.2 of the convention, which provided, in effect, that a former head of state should continue to enjoy immunity with respect to acts performed by him in the exercise of his functions as head of state.
The crucial question was whether the acts of torture and hostage-taking charged against the applicant were done in the exercise of his functions as head of state.
It hardly needed saying that torture of his own subjects, or aliens, would not be regarded by international law as a function of a head of state. Similarly, the taking of hostages, as much as torture, had been outlawed by the international community as an offence.
Whilst recognising that the functions of a head of state might include activities which were wrongful, even illegal, by the law of his own or other states, international law had made plain that certain types of conduct, including torture and hostage-taking, were not acceptable conduct on the part of anyone. That applied as much to heads of state, or even more so, as it did to everyone else: the contrary conclusion would make a mockery of international law.