Describe what is meant by extrinsic aid

Extrinsic aids are materials found outside of the Act in question which may be used by the court in order to aid interpretation.

Explanatory notes are published outside the Act and have been used since 1999. In R v National Asylum Support Service, Lord Steyn noted they can ..cast light on the objective setting or contextual scene of the statute, and the mischief at which it is aimed....

A White Paper was used in W v MPC to determine whether the word remove meant a police officer could use force to take an under 16 year-old home from a dispersal area, it said they did. Hansard can be used where the legislation is ambiguous or obscure or leads to an absurdity (Pepper v Hart). In Pickstone v Freemans it was used to establish why the Equal Pay Act had been passed.

Previous statutes can be used as illustrated by Wheatley. This case involved the Explosive Substances Act 1883, the long title stated it amended the Explosives Act 1875 so the Court of Appeal considered earlier Act too. International treaties may be used to ascertain the overriding objective of the treaty which the Act is intended to comply with. This will often occur when interpreting EU Law. In Fothergill v Monarch Airlines a case about insurance of luggage the Warsaw Convention 1929 was consulted. Committee reports can be used to discover the mischief an Act was aimed to remedy (Allen).

Dictionaries have been used to find the meaning of words. In Fulling it was found oppression as used in the Police and Criminal Evidence Act 1984 should be read as described in the third definition Oxford English Dictionary. Academic studies and commentaries can be used and in Shivpuri the court acknowledged academic argument.