John Marshall is widely revered as "the great Chief Justice," but before joining the Supreme Court in 1801 he had never served a day in judicial robes and lost the only case he argued at the high court.
Earl Warren had worked for 18 years as a prosecutor and was three times elected governor of California. But he had no prior judicial experience. Nor did William Rehnquist, Felix Frankfurter, and Louis Brandeis.
The nomination of White House counsel Harriet Miers to the Supreme Court has sparked debate over her qualifications. Does she have the intellectual heft and constitutional dexterity necessary for the job? And how does her experience compare to the résumés and stature of prior justices?
"People are still learning about Harriet Miers. Hers was not a name that quickly came off everybody's lips when people [asked] who are the most qualified people for the court," says David Yalof, a political science professor and expert on Supreme Court nominations at the University of Connecticut.
But Professor Yalof adds, "The issue has never been most qualified, the issue is qualified."
Who is qualified to sit on the Supreme Court is a determination made on a nominee by nominee basis by at least 51 US senators. There are no set rules for qualification. Although every past justice has been a lawyer, 41 of the 109 justices had no prior judicial experience.
But many of the justices who lacked hands-on experience as a jurist nonetheless had achieved a high level of accomplishment and stature as intellectual or political leaders prior to their nominations.
"Judicial experience is not a prerequisite, but what you look for in place of judicial experience is distinguished experience as a law professor or public official, and Miers really doesn't have either of those two," says Michael Comiskey, a political science professor at Penn State University at Fayette.
One key consideration, scholars say, is the goal of the nominating president.
"She clearly doesn't have the kind of symbolic significance that presidents are sometimes going for in choosing justices - those who you put on the bench because you expect them to be great justices," says Keith Whittington, a politics professor at Princeton University and visiting professor at the University of Texas at Austin.
President Reagan tried it, unsuccessfully, with the nomination of Robert Bork and succeeded with Justice Antonin Scalia, he says. "Earlier in the century Oliver Wendell Holmes was in that mold. Louis Brandeis was in that mold," Professor Whittington says.
But naming the next Holmes or Brandeis is not the only legitimate goal in a high court nomination.
"In lots of other cases you are putting people on who are reliable and have good judgment. You don't know if they are going to be great justices but you think they are going to be good justices, and she [Miers] seems to be more in that mold," he says. "She may emerge as a great justice for all we know, but that is not necessarily the point of picking her."
Scholars are drawing comparisons between Miers and various former justices. Lewis Powell, Abe Fortas, and Brandeis were all lawyers with no judicial experience at the time of their nominations. Powell was president of the American Bar Association, while Miers was head of the Texas Bar Association. Fortas was Lyndon Johnson's personal lawyer prior to being named to the court. Miers was President Bush's personal lawyer and White House counsel prior to her nomination. But the least apt comparison, many analysts say, is with Brandeis.
"The difference between Louis Brandeis and Harriet Miers is that Louis Brandeis was an academic lawyer," says Stefanie Lindquist, a professor of law and political science at Vanderbilt University. "He wrote some very influential law review articles while he was in private practice. So he established intellectual credentials to serve on the court before he was elevated."
She adds, "That is something we are missing with Harriet Miers. We really don't have any paper trail that establishes any intellectual credentials."
Snobbery is no small part of the debate over Miers, analysts say. The fact that she attended Southern Methodist University rather than a top-tier law school like Harvard or Yale is seen by some as a mark against her. Yalof says that although a high number of justices attended elite law schools, not all justices did.
Lewis Powell went to Washington & Lee. Warren Burger attended the St. Paul College of Law. Thurgood Marshall attended Howard University. Hugo Black went to the University of Alabama, and Chief Justice Fred Vinson was a graduate of Centre College in Kentucky.
Yalof says the debate over who is most qualified for the Supreme Court is a false debate. Just because Miers isn't on someone's list of 100 most qualified candidates for a high court post doesn't mean she isn't qualified to do the job, he says.
"No one could possibly have thought in 1956 that William Brennan was on the top 100 list of people to become a justice of the Supreme Court," Yalof says. "At the time of his appointment, William Brennan had been a little-known state supreme court judge in New Jersey for seven years. He was far and away not considered the most reputable justice on his own court," Yalof says. "Was he qualified?"
Judge Brennan, appointed by President Eisenhower, went on to become one of the most influential justices of the 20th century.
In contrast, some high court nominees never measure up. Charles Whittaker was an experienced litigator and corporate lawyer. He served as both a federal judge and an appeals court judge. But was unable to adjust to life as a justice.
"He was one of the great failures in Supreme Court history," Yalof says. "He was overwhelmed by the job and quit after just five years."
Some justices learn and grow on the job.
"People now say that the [Miers nomination] is not a Scalia or Thomas nomination," says Whittington. "But at the time Clarence Thomas was nominated it wasn't clear that Thomas was that kind of nominee either."
He adds, "He has emerged subsequently as somebody who has this kind of strong distinctive voice on the court. It is possible that Miers would as well."
Professor Lindquist says the lack of an academic or judicial paper trail makes it difficult to assess Miers' potential ability to develop or clarify legal and constitutional doctrine.
"My guess is she would be a fine Supreme Court justice, but will she be a great Supreme Court justice - that seems less likely," she says. "John Roberts, on the other hand, is going to become a great Supreme Court justice. Whether or not I agree with all his politics, I think he is likely to be a brilliant Supreme Court justice."