The Federal Rules of Civil Procedure
(a) Examining Jurors. The court may permit the parties or their attorneys to examine prospective jurors or may itself do so. If the court examines the jurors, it must permit the parties or their attorneys to make any further inquiry it considers proper, or must itself ask any of their additional questions it considers proper.
(b) Peremptory Challenges. The court must allow the number of peremptory challenges provided by 28 U.S.C. §1870.
(c) Excusing a Juror. During trial or deliberation, the court may excuse a juror for good cause.