Official Secrets Act: Defence of Necessity (Hansard, 17 March 2004)

§ The Attorney-General (Lord Goldsmith)

Necessity is a common law defence which applies to all crimes. The origin of the defence of necessity in Official Secrets Act cases arises from the case of David Shayler, who was prosecuted for an offence under Section 1 of the Official Secrets Act 1989. In that case the Court of Appeal decided that in addition to the defences specifically provided by the Act the defence of duress or necessity of circumstance was available to defendants charged with an offence contrary to Section 1 of the 1989 Act.

The essence of the defence is that it is available when a defendant commits an otherwise criminal act to avoid an imminent peril of danger to life or serious injury to himself or towards somebody for whom he regards himself as responsible. That person need not be named and may not be identifiable. If it is not possible to name the person it must be possible to identify them by reason of the threat to them which may be avoided by the defendant taking action. The defendant has a responsibility for them because he is placed in a position where he has a choice whether to take or not to take the action which will avoid them being injured. The act done should be no more than is reasonably necessary to avoid the harm feared and the harm resulting from the act should not be disproportionate to the harm avoided.

The defence of necessity has been used in the case of David Shayler and was raised by the defence in the case of Katharine Gun.