What is the legal test for making a peremptory challenge against a potential juror?

Although the two challenges work in tandem, peremptory challenges differ considerably from challenges for cause. Challenges for cause, while unlimited in number, allow the removal of panel members only "on a narrowly specified, provable, and legally cognizable basis of partiality," id. at 220, 85 S.Ct. at 836, such as a personal relationship with a party, witness, or attorney in the litigation, or a biased state of mind concerning a party or issue in the case. The number of prospective jurors who may be excused for cause is unlimited. 28 U.S.C. 1870. Challenges for cause require the challenging party to articulate clearly on the record the precise reason for challenging the potential juror, but the decision whether to exclude a panel member for cause is vested in the trial court. Gray v. Mississippi, 481 U.S. 648, 652 n. 3, 107 S.Ct. 2045, 2048 n. 3, 95 L.Ed.2d 622 (1987) ("[M]otion to excuse a venire member for cause ... must be supported by specified causes or reasons that demonstrate that, as a matter of law, the venire member is not qualified to serve.").