In the last 30 years, almost all justices had served on United States Courts of Appeals, presumably because that gave the presidents who appointed them a way to assess how they might decide.

But in the history of the court, drawing on the pool of appeals judges is a relatively recent trend. Of the 109 people who have been on the Supreme Court, 41 had no previous judicial experience, according to the "Guide to the U.S. Supreme Court," published by Congressional Quarterly.

Many of those have been among the most influential justices - John Marshall, Earl Warren, Louis D. Brandeis, Robert H. Jackson, Felix Frankfurter and William H. Rehnquist, to name a few.

As recently as the early 1970's, prior judicial experience was not much of a factor in picking Supreme Court candidates. The early Warren court in the 1950's, for instance, included three former senators, two former attorneys general and Chief Justice Warren, a three-term governor of California and the Republican vice-presidential nominee in 1948.

Among those who joined the court from 1962 to 1972, in addition to Justice Rehnquist, who was an assistant attorney general, were Arthur J. Goldberg, a labor lawyer who had been labor secretary; Abe Fortas, a federal official in the New Deal who became a prominent corporate lawyer; Byron R. White, who was deputy attorney general; Lewis F. Powell Jr., a top lawyer who had been president of the American Bar Association and president of the Richmond, Va., School Board; and Thurgood Marshall, who had been an appeals court judge for four years but whose main experience was as a civil rights lawyer and solicitor general.

Since 1972, every justice has come directly from a federal appeals court except Sandra Day O'Connor, who was on the Arizona Court of Appeals.