Experience needed? The long history of nonjudge justices.
Nearly half of justices had no prior experience on the bench.
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.