Early experience as a barrister was gained on the border circuit in Cavan- Monaghan where he displayed an enormous appetite for work. His arrival on the bench coincided with a period of discontent with the accepted order in the post-Independence Catholic-leaning state.
The historian Joe Lee, in his book Ireland 1912-1985 (1989), saw Walsh's elevation as part of the overturning of the monolithic state ethos fostered under Cosgrave, de Valera and Costello governments when dissidents "either emigrated or were marginalised". Walsh was "the outstanding legal reforming mind of his generation", Lee wrote.
Perhaps more than any other decision, Walsh's 1972 ruling in Byrne vs Ireland, allowing the citizen to sue the state, altered legal history. It ended a British-inherited tradition based on the presumption that, as the barrister Seamus McKenna put it, "the Crown could do no wrong".
Other landmark judgments echoing this commitment to the individual's rights included his 1966 ruling that bail could not be withheld simply because of a belief that a defendant might commit further offences if freed.
In the landmark 1973 McGee case, he ruled the 1935 ban on the importation of contraceptives was unconstitutional. This encouraged a more liberal social climate and a gradual improvement in the status of Irish women after generations of hardship associated with rearing large families on limited incomes.
His 1974 appointment as leader of Dublin's side on the Anglo-Irish Law Enforcement Commission, a creation of the Sunningdale Agreeement, sent in the state's most trenchant defender of civil rights at a time of international anger over treatment of prisoners in custody in Northern Ireland.
He retained his independent thinking until the end of his career, with a landmark 1987 decision forcing the Dublin government to hold a referendum before it could ratify the Single European Act. Controversially, he also protected the "political exception" when the Supreme Court directed that suspects not be extradited where they were likely to suffer ill-treatment.
This came in the case of the Maze escapers Dermot Finucane and James Pius Clarke, the latter having been a victim of alleged sustained beatings during earlier custody in Northern Ireland. The five judges all bluntly agreed on "the probable risk that if Finucane were returned [to Northern Ireland] he would be assaulted or injured by the illegal actions of prison officers".
Earlier, Walsh's hostility to extraditing suspects back to that regime had seen sparks fly between himself and a colleague on the Law Enforcement Commission, Mr Justice Seamus Henchy. The two had other disagreements, notably over homosexuality, on which Henchy took the more liberal view in the long-running saga which led eventually to decriminalisation.
Walsh was also opposed to what he felt were over-liberal attitudes which he feared might encourage demand for abortion by making it an easy option and backed the anti-abortion clause in the Irish Constitution.
Brian Walsh, barrister and judge: born Dublin 23 March 1918; called to the Irish Bar 1941, Inner Bar 1954; High Court judge 1959-61, Supreme Court judge 1961-90; member, World Association of Judges 1966-98; leader of Irish delegation on Anglo-Irish Law Enforcement Commission, 1974; President, Irish Law Reform Commission 1975-85; member, European Court of Human Rights 1980-98; married 1944 Noreen Joyce (one son, four daughters); died Dublin 9 March 1998.