US Supreme Court Justice John Paul Stevens, a one-time centrist maverick who became a powerful leader of the Court's liberal wing, announced his retirement on Friday (9 May), just 11 days short of his 90th birthday.

When Stevens departs at the end of the current term in late June or early July, he will have been one of the oldest and longest-serving justices in US history, appointed by President Gerald Ford in 1975, and the last justice with World War II service.

Stevens' departure sets up the likelihood of a contentious confirmation battle this summer, almost no matter who President Barack Obama nominates to replace him. Speculation in Washington immediately settled on Solicitor General Elena Kagan and federal appeals judges Diane Wood and Merrick Garland as the most likely possible successors, though other names ranging from Homeland Security Secretary Janet Napolitano to Minnesota Democratic Senator Amy Klobuchar have also been mentioned.

Although a new Obama-appointed justice may vote the same way Stevens would in most cases, the stakes are high because of Stevens' role as a crucial strategist within the Court. Because of his seniority, Stevens was also the justice who assigned the writing of opinions whenever he was in the majority and Chief Justice John Roberts Jr was not. Justice Antonin Scalia, who joined the Court in 1986, will be the most senior associate justice when Stevens leaves.

"They are enormous shoes to fill," said former Stevens law clerk Pamela Harris, now executive director of the Supreme Court Institute at Georgetown University Law Center. "He is a Gerald Ford Republican and is at the very left of this Court. Both things are true."

Diane Amann, a University of California, Davis School of Law professor who is writing a book on Stevens' jurisprudence, said, "In his 40 years as a federal judge, Justice Stevens has helped to shape the law's response to the issues of our day. He has influenced how our society considers criminal justice and capital punishment, gay rights and reproductive freedom, the role of the government in fostering diversity and the powers of the president in time of crisis."

Though not unexpected, the timing of Stevens' announcement came as a surprise in Washington. Stevens was at his second home in Fort Lauderdale, Florida, and his letter was conveyed to the White House counsel's office by an unnamed Court representative. White House counsel Robert Bauer phoned Obama with the news while Obama was on Air Force One.

In his letter, Stevens pointedly indicated he was announcing it now so his successor could be confirmed "well in advance" of the beginning of the Court's fall term in October.

Obama, reacting to Stevens' announcement, also pledged to move quickly to find someone who would match Stevens "independent mind, a record of excellence and integrity, a fierce dedication to the rule of law, and a keen understanding of how the law affects the daily lives of the American people."

Underscoring his criticism of the Supreme Court's 21 January decision in Citizens United v Federal Election Commission, Obama also said he would look for someone who understands that corporate interests should not "drown out" the voices of average citizens. Stevens was the leading dissenter in the 5-4 Citizens United case, which relaxed regulation of corporate and union participation in political campaigns.

'Consummate dealmaker'

Born in Chicago into a wealthy family that built what was once the world's largest hotel, Stevens had a modest manner, often sporting an impish smile above his trademark bow ties on and off the bench. When he addressed a lawyer during oral argument, Stevens would often start meekly with, "Counsel, may I interrupt." Then he would ask what lawyers often found to be the most penetrating or difficult question.

"It's a modesty born of extreme confidence. He knows he is smart," said Chicago journalist Bill Barnhart, whose biography of Stevens will be published soon. "He enjoys being a facilitator, being engaged in the process of compromise." By most accounts, Stevens is the only current justice who writes the first drafts of at least some of his opinions, and his ability to write quickly helped him shape coalitions and compromises early, when drafts are being circulated among justices.

"He is the consummate dealmaker," said Mayer Brown partner Andrew Pincus, a frequent advocate before the Court. "When I appear before him, he always seems quicker and better. I feel like I'm the one who has aged, not him."

Stevens leaves a diverse legal legacy, authoring landmark decisions ranging from Reno v ACLU, the 1997 decision that anointed the internet with broad First Amendment protection, to Chevron v Natural Resources Defense Council [1984], which has guided the administrative state ever since. In Rasul v Bush and Hamdan v Rumsfeld, Stevens asserted the role of the courts even in wartime determinations of the fate of detainees held at Guantanamo Bay. Those rulings harkened back to Stevens' own role as a law clerk to Justice Wiley Rutledge in a 1948 post-World War II ruling Ahrens v Clark. During his own military service, Stevens was a code-breaker during World War II.

A 2005 decision by Stevens, Kelo v City of New London, triggered a broad public backlash by upholding a city's plan to take a private home by eminent domain for the benefit of a private development. He later said he personally disagreed with the decision, but was compelled by Court precedents to rule against the homeowner. He also vigorously denied the decision was an example of judicial activism, as critics had charged.

Another memorable ruling by Stevens came in 1997 in Clinton v Jones, regarding Paula Jones' civil lawsuit against President Bill Clinton – which launched a chain of events leading to Clinton's impeachment. "It appears highly unlikely to occupy a substantial amount of [President Clinton's] time," Stevens wrote. Along with assessments of the Titanic's seaworthiness, that may rank among the last century's most inaccurate predictions. In a post-impeachment speech, however, Stevens defended the decision and doubted that any justice would change his or her vote even in light of what had transpired since.

The National Law Journal is a US sister title of Legal Week.