He became Queen's Counsel (NI) in 1970. From 1979 to 1988, he was (as Sir Brian Hutton) a High Court judge. In 1988 he became Lord Chief Justice of Northern Ireland, becoming a member of the Privy Council of Northern Ireland, before moving to England in 1997 to become a Lord of Appeal in Ordinary. He was consequently granted a life peerage as Baron Hutton, of Bresagh in the County of Down.
On March 30, 1994 as Lord Chief Justice of Northern Ireland, he dismissed Private Lee Clegg's appeal against his controversial murder conviction. On March 21, 2002, Lord Hutton was one of four Law Lords to reject David Shayler's application to use a "public interest" defense as defined in section 1 of the Official Secrets Act at his trial.
Lord Hutton represented the Ministry of Defence at the inquest into the killing of civil rights marchers on "Bloody Sunday". Later, he publicly reprimanded Major Hubert O'Neil, the coroner presiding over the inquest, when the coroner accused the British Army of murder, as this contradicted the findings of the Widgery Tribunal.
Lord Hutton also came to public attention in 1999 during the extradition proceedings of former Chilean dictator Gen. Augusto Pinochet. Pinochet had been arrested in London on torture allegations by request of a Spanish judge. Five Law Lords, the UK's highest court, decided by a 3-2 majority that Pinochet was to be extradited to Spain. The verdict was then overturned by a panel of seven Law Lords, including Lord Hutton on the grounds that Lord Hoffmann, one of the five Law Lords, had links to human rights group Amnesty International which had campaigned for Pinochet's extradition.
In 1978 he defended Britain in the European Court of Human Rights when it was found guilty of torturing internees without trial. He sentenced 10 men to 1,001 years in prison on the word of 'supergrass' informer Robert Quigley who was granted immunity in 1984.
Lord Hutton was appointed by the Blair government to chair the inquiry into the death of the British scientist Dr David Kelly at the heart of the September Dossier controversy. The inquiry commenced on August 11, 2003. Many observers were surprised when he delivered his report on January 28, 2004. Lord Hutton cleared the British Government in large part. His criticism of the BBC was regarded by some as unduly harsh; one critic commented that he had given the "benefit of judgement to virtually everyone in the government and no-one in the BBC.
Peter Oborne wrote in The Spectator in January 2004: "Legal opinion in Northern Ireland, where Lord Hutton practised for most of his career, emphasises the caution of his judgments. He is said to have been habitually chary of making precedents. But few people seriously doubt Hutton's fairness or independence. Though [he is] a dour Presbyterian, there were spectacular acquittals of some very grisly IRA terrorist suspects when he was a judge in the Diplock era."
In the case Q v JOHN CHRISTOPHER WALSH, the appellant had been given the Trial Transcripts on 24th September 1993, and informed that his Appeal would be only in 3 days time. He was not permitted to consult with any legal advisor prior to the Appeal. The Appellants legal representatives protested at this and also informed the Court that they were not properly prepared. Hutton LCJ ruled that the Appeal was still to continue. The Appealant accused Hutton LCJ, Carswell LJ, and Kelly LJ of “railroading” him. The Appeal was adjourned and a new panel of judges were selected.
Sinn Féin and former IRA member (volunteer) Danny Morrison wrote in The Guardian: "Although in the Belfast high court Hutton occasionally acquitted republicans and dismissed the appeals of soldiers, nationalists generally considered him a hanging judge and the guardian angel of soldiers and police officers. [...] I was amused at the response of sections of the media and British public [to Hutton's exonerating the Blair government]. Do they know anything about how the establishment works?"