The Court has considered a series of cases addressing the question of juror bias in capital cases and the defendant's right to a fair trial guaranteed by the Sixth and Fourteenth Amendments. These cases have focused either on jurors' attitudes toward the death penalty--i.e., whether they are strongly opposed or in favor of the death penalty--or racial bias. In deciding these cases, the Court has tried to give guidance with regard to the appropriate scope of voir dire.
A. Death-Qualified Jurors -
In Witherspoon v. Illinois, 391 U.S. 510 (1968), the Court held "that a sentence of death cannot be imposed or recommended if the jury that imposed or recommended it was chosen by excluding veniremen for cause simply because they voiced general objections to the death penalty or expressed conscientious or religious scruples against its infliction." Id. at 522. The Court observed that even someone opposed to the death penalty "can make the discretionary judgment entrusted to him by the State and can thus obey the oath." Id. at 519. A state, however, may exclude those jurors who would automatically vote against the death penalty or those jurors whose attitudes about the death penalty would affect their decision regarding the defendant's guilt. Id. at 522, n.21.
Later, the Court made clear that Witherspoon did not hold that the state could exclude only those jurors who would automatically vote against capital punishment. In Wainwright v. Witt, 469 U.S. 412 (1985), the Court held that the standard for excluding a juror because of his views in opposition to the death penalty is "whether the juror's views would 'prevent or substantially impair the performance of his duties as a juror in accordance with his instructions and his oath.'" Id. at 424 (quoting Adams v. Texas, 448 U.S. 38, 45 (1980)). The Court treated the question of jurors beliefs with regard to the death penalty as simply a routine inquiry into juror bias governed by Sixth Amendment standards applicable to all cases rather than the Eighth Amendment's prohibition against cruel and unusual punishment. Id. at 423.
The Court also noted that trial judges have historically been charged with determining whether a prospective juror harbors any bias. Id. at 428. If the trial judge, who is best placed to evaluate a juror's credibility, receives the impression that the juror would be unable to follow the law, the judge can remove the juror for cause. Id. at 425-26.1
B. Reverse-Witherspoon -
Just as the state may excuse for cause those jurors whose beliefs against the death penalty would substantially impair their performance of their duties as jurors, a defendant may excuse for cause those jurors whose beliefs in favor of capital punishment would lead them to ignore the court's instructions, not consider mitigating circumstances, and vote for the death penalty in every case. Morgan v. Illinois, 504 U.S. 719 (1992). This violates "the requirement of impartiality embodied in the Due Process Clause." Id. at 729.
If the defendant has the right to excuse for cause jurors who hold such views, and because the defendant must demonstrate that the juror lacks impartiality, voir dire must be adequate to uncover such bias. Id.2 It is not enough simply to ask the jurors if they could be fair and follow the law. Id. at 734-35. The defendant must be able to ascertain whether the prospective jurors find mitigating evidence irrelevant or even not worth their consideration. Id. at 736.
C. Racial Bias -
In Turner v. Murray, 476 U.S. 28 (1986), the Court held that a capital defendant is entitled to voir dire on the question of racial bias. "Because of the range of discretion entrusted to a jury in a capital sentencing hearing, there is a unique opportunity for racial prejudice to operate but remain undetected." Id. at 35. Thus, unless adequate voir dire is conducted, beliefs that blacks are more violence prone or morally inferior could influence a juror’s determination about the presence of aggravating factors. Id. Racist beliefs could also cloud a juror's view of evidence in mitigation. Id. Without adequate voir dire, there is an unacceptable risk "of improper sentencing in a capital case." Id. at 37. The Court, however, stressed that its holding was limited to cases in which the state was seeking the death penalty. In addition, the Court held only that Turner was entitled to a new sentencing phase, not a new trial on guilt-or-innocence. Id.
D. Jury Sentencing -
The Court over the years rejected numerous challenges to death penalty systems that did not require that a jury make the sentencing decision or that did not at least require that a jury make the findings concerning the existence of aggravating and mitigating circumstances. See, e.g., Clemons v. Mississippi, 494 U.S. 738, 745 (1990) (“Any argument that the Constitution requires that a jury impose the sentence of death or make the findings prerequisite to imposition of such a sentence has been soundly rejected by prior decisions of this Court.”) More recently, in Ring v. Arizona, 536 U.S. 584 (2002), the Court changed course in part and ruled that where an aggravating factor creates eligibility for a sentence of death, there is a Sixth Amendment right to a jury finding on whether or not the aggravating factor has been proven by the prosecution beyond a reasonable doubt.3
1 Because a determination of juror bias "involves credibility findings whose basis cannot be easily discerned from an appellate record," the trial judge's findings are accorded a presumption of correctness. Witt, 469 U.S. at 429; see also Uttecht v. Brown, 127 S.Ct. 2218, 2233 (2007) (reviewing courts are to accord deference to the trial court’s findings).
2 See also Lockhart v. McCree, 476 U.S. 162, 170, n.7 (1986) (state must be given the opportunity to identify through voir dire jurors' views about the death penalty).
3 Because the aggravating factor at issue in Ring was not related to a prior conviction, the Court’s holding in Almendarez-Torres v. United States, 523 U. S. 224 (1998) -- that the fact of prior conviction may be found by the judge even if it increases the statutory maximum sentence – was not challenged. 536 U.S. at 597 n. 3.