In Morgan v. Illinois the United States Supreme Court settled the "reverse- Witherspoon" question. The Court held that a trial court in a capital case must, upon the defendant's request, specifically inquire into a prospective juror's views on capital punishment and that a potential juror who would always vote for a sentence of death, regardless of the facts, must be struck for cause. Further, the Court stated that the presence of even one partial juror on a defendant's panel offends the defendant's Fourteenth Amendment right to a fair and impartial jury and the sentence may not stand.
Before Morgan, trial courts often refused a defendant's request for a specific inquiry into whether any prospective jurors would always vote for the death penalty upon conviction of a capital crime. Trial judges maintained that a general question concerning the prospective juror's ability to follow the law sufficed to identify impartial jurors. However, the Court held that such questions are inadequate. When a trial court refuses the defendant's request for the specific question of a potential juror's vote on death sentences, the sentencing phase must be retried.
Thomas Joshua R. Archer, Morgan v. Illinois: The Defense Gets the Reverse-Witherspoon Question, 44 Mercer L. Rev. 997 (1993).