FYI from Wikipedia:
The Constitution does not explicitly establish any qualifications for Justices of the Supreme Court. However, Presidents normally nominate individuals who have prior legal experience. Typically, most nominees have previous judicial experience, either at the federal or state level. Several nominees have formerly served on federal Courts of Appeals, especially the Court of Appeals for the District of Columbia Circuit, which is often considered a stepping stone to the Supreme Court. Another source of Supreme Court nominees is the federal executive branch?in particular, the Department of Justice. Other potential nominees include members of Congress and academics. On the current Supreme Court, seven Justices previously served on federal courts (including three on the D.C. Circuit); two served on state courts; three were former law school professors; and three held full time positions in the federal executive branch.