After Miers, everybody and his grandmother are qualified for the Supreme Court. [Uh-HYUCK! Uh-HYUCK!]
The Constitution does not explicitly establish any qualifications for Justices of the Supreme Court. In fact it does not even specify citizenship or age as it does for the executive and legislative branches. However, Presidents normally nominate individuals who have prior legal experience. Typically, most nominees have 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.
Nominees to the Supreme Court, as well as to lower federal courts, are evaluated by the American Bar Association's Standing Committee on Federal Judiciary. The panel is composed of fifteen federal judges (but not Supreme Court Justices), including at least one from each federal judicial circuit. The body assesses the nominee "solely to professional qualifications: integrity, professional competence and judicial temperament," and offers a rating of "well qualified," "qualified," or "not qualified." The opinions of the committee bind neither the President nor the Senate; however, they are generally taken into account.