A classic statement of the importance of the value of freedom of expression:
Freedom of expression is, of course, intrinsically important: it is valued for its own sake. But it is well recognised that it is also instrumentally important. It serves a number of broad objectives. First, it promotes the self fulfilment of individuals in society. Secondly, in the famous words of Mr. Justice Holmes (echoing John Stuart Mill), “the best test of truth is the power of the thought to get itself accepted in the competition of the market.”: Abraham v. United States 250 U.S. 616, at 630 (1919), per Holmes J. (dissent). Thirdly, freedom of speech is the lifeblood of democracy. The free flow of information and ideas informs political debate. It is a safety valve: people are more ready to accept decisions that go against them if they can in principle seek to influence them. It acts as a brake on the abuse of power by public officials. It facilitates the exposure of errors in the governance and administration of justice of the country: see Stone, Seidman, Sunstein and Tushnett, Constitutional Law, 3rd ed., (1996), 1078-1086. It is this last interest which is engaged in the present case. The prisoners argue that in their cases the criminal justice system has failed, and that they have been wrongly convicted. They seek with the assistance of journalists, who have the resources to do the necessary investigations, to make public the wrongs which they allegedly suffered.
R (Simms) v Secretary of State for the Home Department [2000] 2 AC 115 (Lord Hoffman).