Becoming a TD and early social influences

Having a family connection to the party, Costello had been a member of Fine Gael since joining college. In 1951, at the age of just 24, he was elected to Dáil Éireann as a Fine Gael TD for the Dublin North-West constituency during that year's general election. He was the youngest member of the house at the time, earning him the informal title of Baby of the Dáil. The following years would significantly influence Costello's political views; his exposure to the poor living conditions of his constituents in Dublin North-west radically altered his views on housing. In 1953, Costello married Joan Fitzsimons. With Joan, Costello would go on to have four sons and two daughters. One of these sons was later found to have autism, and the cause of children with special needs quickly became an area of special concern for Costello, particularly as "his elder brother Wilfrid had been left with a mild mental disability during birth".^[5] Costello co-founded the Association of Parents and Friends of Mentally Handicapped Children (renamed St Michael's House in later years) in 1955, and aided in the fund-raising for a daycare centre in 1956 for the education of children who were mentally disabled. The fundraising would lead to the daycare centre becoming known as an official school in 1960. Beginning in 1956 until he died in 2011, Costello was the St Michael's House president, making him ultimately responsible for 170 centres across the Dublin region.^[4]

Stepping out of his father's shadow

After the 1954 general election, John A. Costello became Taoiseach for a second time, while Declan retained his seat. Although Declan was not placed in a cabinet position, he had a measure of influence over his father and the government. Considered the most radical of those who advised his father, Declan pushed against the austerity measures of Finance Minister Gerard Sweetman, who in time would become a great rival and adversary. Following the 1957 Irish general election, in which Fine Gael and its coalition partners lost control of the government to Fianna Fáil, Costello became Fine Gael's spokesperson on foreign affairs. In this capacity, Costello asserted liberal, anti-communist views while encouraging European integration amongst the growing European Economic Community organisation. Two issues, in particular, drew his attention: the government's support for the withdrawal of Russian and US forces from Europe, and the support given for a resolution favouring the inclusion of People's Republic of China as part of the UN.^[6][4]

It was also at this time that he began to advocate that Fine Gael move politically leftward in order to broaden its image beyond that of simply being a status quo, bourgeois party, as well as to make it a more attractive coalition partner to the Labour party. Towards the end of the 1950s, Costello began to assert himself even more in Fine Gael; alongside a growing collection of progressives within the party, Costello founded a monthly political magazine as well as a research and study group focused on developing new policies for the party. However, to their disappointment, Costello and his faction found the rest of Fine Gael slow and sluggish in response to their new ideas, and thought that they were against complex making of policies and the voicing of personal differences in public. Following his father's retirement from politics in 1959, longstanding member James Dillon became leader of the party and Costello felt his ability to influence policy-making slipping away.^[4]

The Just Society

In 1963, Costello found an attempt to change party policy suppressed by the party leadership. Regardless, in April 1964 Costello broke party protocols and circulated a proposal to radically alter Fine Gael's economic policies. At this point Costello did not expect his proposal to gain traction within the party; instead it was to be used as a pretext to leave the party and politics, and to turn to his work as a lawyer. Costello neither canvassed other party members nor spoke to the press following the circulation of his document. However, to his surprise, Costello's ideas began to pick up momentum with Fine Gael backbenchers, who had begun to crave a means by which Fine Gael could differentiate itself from Fianna Fáil. Journalists too began to take an interest in the initiative, sensing a new direction emerging in Irish politics.^[4]

Costello began to argue his case with the Fine Gael frontbench, and using his honed debating skills, dominated proceedings. Unable to outright repudiate Costello's ideas, the frontbench sought to bog down discussions and drag them out. However, in March 1965 the party was shocked by the development that Fianna Fáil were seeking to hold a general election. With no time to develop a separate manifesto other than what Costello was proposing, his ideas were given the green light. He would go to expand his initial policy document into a 30,000-word manifesto called Towards a Just Society, which would have a major impact on the party for many decades.^[4]

Towards a Just Society called for a radical shift in the Irish economy to something closer to a social democratic mixed economy; it called for production objectives in the private-sector, earnings and credit from banks to be controlled, no discrimination of women's wages, industrial school reformation, lower use of indirect taxes, free near-universal health care with the decision of what doctor to have, and an educational system that permits moving to university despite being wealthy or not. Although radical, because of its length Towards a Just Society was difficult to communicate to the Irish public in the short time the party had to campaign in the 1965 Irish general election. Fine Gael did not make gains in the elections, and afterwards, Labour were rattled by the move, and in response, they themselves also moved more to the left. However, the Just Society's critique of public services in Ireland forced Fianna Fáil to alter their policies, and during the election, they made promises in regards to housing, health and welfare. Costello's political profile was enhanced by the Just Society concept.^[4]

After the 1965 election

Costello continued his work as a TD for Dublin North-West and came to seek the leadership of Fine Gael to continue his Just Society project. His opportunity came quickly, as following the 1965 election James Dillon stepped down as leader of the party. However, Costello was politically outmanoeuvred by Dillon and Sweetman who moved rapidly to place Liam Cosgrave as Dillon's successor, and were successful.^[7] In the aftermath, a dejected Costello sought to become the party's spokesperson for Finance, but instead was handed the position of spokesperson for health and social welfare. Costello was further frustrated by Cosgrave's limp espousal of the Just Society concept.^[4]

Post-1965, Costello's health once again began to haunt him, and his position as de facto leader of Fine Gael's progressive faction increasing fell to a young Garret FitzGerald, whom Costello himself had brought into the party. Like Costello, Fitzgerald was the son of a stalwart of the party, being the son of Desmond Fitzgerald, and like Costello Fitzgerald shook off the traditional conservatism of his father to embrace a more social liberal outlook. In February 1967, Costello said that he will not aim for the Dáil again and focused on his successful legal work. Michael O'Leary of Labour lamented that Irish politics would be losing a "young man of great courage and idealism".^[6] Fine Gael backbencher John Healy wrote "He has been lost to Fine Gael almost from the day Mr Liam Cosgrave took over, reshuffled his deck and left Declan Costello on the fringe of things. Declan Costello deserved better: he did not get it".^[4][6]

In 1968/1969, Costello successfully defended Sean Bourke against extradition to the United Kingdom in relation to his assisting George Blake, the Soviet double agent, to escape from prison.^[6] In 1972 Costello unsuccessfully defended journalist Kevin O'Kelly against contempt of court charges, arising from a radio interview he conducted with Provisional IRA leader Seán Mac Stiofáin.^[6] O'Kelly was sentenced to three months in prison.^[8]

Although outside the confines of Fine Gael, Costello continued to remain in the political sphere. He would host parties and meetings of Fine Gael and Labour members, where they would discuss possible Fine Gael/Labour coalitions, how to dislodge Cosgrave as leader of Fine Gael and even the possibility of forming a new political party. When the prospects of an actual Fine Gael/Labour coalition became more and more tangible from 1970 onwards, Costello announced he would stand for the Dáil in the next election. He stood in a different constituency from his previous one, moving to Dublin South-West, but nevertheless was elected at the 1973 Irish general election. The inclusion of a progressive such as Costello on the Fine Gael ticket helped cement the Fine Gael/Labour coalition.^[4]

Attorney General of Ireland

Costello served in the cabinet of Liam Cosgrave as Attorney General of Ireland

When Fine Gael returned to government in 1973, Costello was appointed Attorney General under Taoiseach Liam Cosgrave. By focusing on his successes in the legal profession, Cosgrave was able to prevent Costello from holding a ministry without dismissing him out of hand. Regardless, Costello accepted the position, even though it actually meant he would earn less money than if he continued his private law practice. As per the custom in Ireland, Costello as Attorney General rarely spoke in the Dáil. However, he was influential amongst the cabinet, where his views were held in high regard by the minister for foreign affairs Garret FitzGerald, and members of Labour, such as Justin Keating who was the minister for industry and commerce.^[4]

As attorney general, Costello took part in the negotiations for the Sunningdale Agreement. Costello took his cues from John Hume, the leader of the Social Democratic and Labour Party, the main nationalist party in Northern Ireland at the time, and like Hume was successful in pushing for very capable all-Ireland establishments. When the agreement was challenged as unconstitutional, it was Costello's role to defend it. He did so successfully in the courts, but his ultra-aggressive defence of it contributed to the disdain in which Unionists held it, and in turn, they would cause the collapse of the agreement in early 1974.^[4]

Costello pushed, unsuccessfully, for family law in Ireland to be updated so that it would be more sympathetic to forsaken wives, mothers who were not married, and out of wedlock-born children, as well as other more liberal values. In 1974, he also was the main person to promote a bill that would have liberalised the purchase of contraceptives in Ireland by allowing married couples to access them without barrier. However, the bill failed when six members of Fine Gael, including most prominently of all Taoiseach Liam Cosgrave, voted against it.^[9]

As Attorney General, Costello refused requests by members of the coalition to have their constituents' minor criminal charges squashed, an established practice in Ireland. Costello sought to depoliticise the office of Attorney General, and successfully did so in 1975 upon his establishment of the Director of Public Prosecutions's office. From then on, briefs for criminal cases would be apportioned despite party relationship. Finding many of his attempts to reform Irish law stifled by a combination of bureaucratic lethargy and defiance from vested interests, Costello founded the Law Reform Commission in 1975. Although the Law Reform Commission lacked resources or political support, in time it was able to produce significant legal reform in Ireland thanks to its institutional status.^[4]

During his time as Attorney General, Costello proved to be a thorn in the side of the British government. Costello was vocal in his belief that, wherever possible, the Irish state should refuse to extradite Provisional Irish Republican Army prisoners to the United Kingdom. Costello's stance was born out of his experience in 1973 when he was in charge of Ireland's case with the European Commission of Human Rights being against the UK for the internment and torture of nationalists in Northern Ireland. Costello had been convinced he needed to establish precedent in international law on the matter, regardless of diplomatic concerns. Engaging the political right and tabloid press in the UK, Costello was able to prove in court that the British state was illegally using sensory deprivation techniques on prisoners. In 1977, it was decided by the court that the prisoners were treated harmfully before giving the verdict of the UK being cleared of torture.^[4]

For having created the Office of the Director of Public Prosecutions and the Law Reform Commission, Costello has been called the "most consequential attorney general in the state's history".^[4]

The X Case

In February 1992, the Attorney General, Harry Whelehan, sought an injunction from the High Court to restrain a 14-year-old girl, known as "X", who was a victim of statutory rape, from travelling outside the State to obtain an abortion.^[6] The case came before Costello, who was forced to weigh the argument that there was a high probability of "X" committing suicide unless she were permitted to travel against "right to life of the unborn" contained in the constitution following the Eighth Amendment in 1983. Costello held "that the certainty of the fetus dying in an abortion outweighed the possibility of a suicide", and granted the injunction.^[4] The response was explosive; there was international condemnation of the decision. On 26 February the Supreme Court overturned Costello's ruling. Costello's ruling was opined to be in breach of European law, which "protects the right to travel for services lawfully provided" in other EU countries, although an official ruling on that thinking was avoided. In November 1992, a constitutional amendment to permit travel was approved in a referendum.^[4]

President of the High Court

Although his decision in the X Case had shocked Costello's liberal admirers, his appointment as President of the High Court in 1995 was not judged to be controversial, partly because he had been acting president since 1991. As president, Costello created procedures which allowed "urgent cases to be dealt with faster" before retiring as a judge in December 1997.^[4] Costello's final act as a public figure was "to head an inquiry into the tax evasion conspiracy directed by the Guinness and Mahon Bank".^[4] Having taken the position in 1999, he retired from it in 2000 upon medical advice.^[4]