Factbox: Supreme Court's Stevens to retire

WASHINGTON (Reuters) - Supreme Court Justice John Paul Stevens announced on Friday that he would be retiring.

Following are some key facts about Stevens:

ONE OF THE OLDEST AND LONGEST-SERVING JUSTICES IN HISTORY

Stevens, who was appointed to the court in 1975 by President Gerald Ford, is the fourth-longest-serving justice in the court's history.

The record was set by Justice William Douglas, whom Stevens replaced. Douglas retired after 36 years and seven months on the court.

Stevens, who will turn 90 on April 20, is the second oldest justice in court history. Justice Oliver Wendell Holmes retired in 1932 just two months before his 91st birthday.

FROM MODERATE REPUBLICAN TO LEADER OF LIBERALS

During his career, Stevens evolved from a moderate Republican to the leader of the four liberal justices as the Supreme Court moved to the right.

Stevens initially carved out a record on the bench as a maverick, with a reputation as a nonpartisan, highly independent jurist.

At the ideological center of the court, Stevens often wrote separate concurring or dissenting opinions that reflected his hard-to-label judicial philosophy.

But as the court moved to the right in the 1990s and this decade, Stevens became the leader of the liberal faction that included three other justices.

A master tactician, he often built coalitions that won a majority, such as in rulings that rejected the Bush administration's legal positions in the war on terrorism.

Stevens authored the court's opinion that detainees at the U.S. military base at Guantanamo Bay in Cuba can challenge their confinement in U.S. courts. He also wrote the opinion that struck down as illegal the military tribunal system for the terrorism suspects.

OFTEN WROTE THE COURT'S MAJOR BUSINESS CASES

Stevens, who had been a specialist as a private attorney in Chicago on antitrust laws barring anti-competitive acts by big companies, often wrote the court's major business cases.

In two cases last term, Stevens wrote for the court majority that tobacco firms can be sued for deceptive advertising of "light" cigarettes and pharmaceutical companies can be held liable for damages for harm from medicines even if they carry warnings approved by federal regulators.

In 2007, Stevens authored the court's opinion that handed the Bush administration a defeat by ruling U.S. environmental officials have the power to regulate greenhouse gas emissions that contribute to global warming.

And in 1997, Stevens extended free-speech rights to cyberspace in his landmark ruling that struck down a federal law that restricted indecent pictures and words on the Internet.

STILLS PLAYS TENNIS, SPENDS TIME IN FLORIDA

Stevens remains an avid tennis player, golfer and swimmer. He and his wife, Maryan, have a condominium in Fort Lauderdale, Florida, where he spends as much time as possible when the court is in recess. He works by computer and uses e-mail to stay in touch with his office in Washington.

Born in Chicago, Stevens served in the Navy during World War II, and helped crack Japanese code. He graduated from Northwestern's law school and worked at the Supreme Court as a law clerk to Justice Wiley Rutledge in 1947-48.

A sharp, but polite, questioner of attorneys who argue before the Supreme Court, Stevens wears a bow tie with his black robes.

(Reporting by James Vicini, Editing by David Alexander)