What is the current state of the law on peremptory challenges?

Though the peremptory challenge is one of the accused's "most important rights," neither the number of peremptories nor the manner of their exercise is constitutionally secured. United States v. Turner, 558 F.2d 535, 538 (9th Cir. 1977) (citations omitted). The district court has wide discretion in setting the procedures for the exercise of peremptory challenges, but "the method chosen by the district court must not unduly restrict the defendant's use of his challenge." Id. In addition, the defendant must be given adequate notice of the system that the court uses for exercising peremptories. Id.