In the case of Witherspoon v. Illinois, 1967, the U.S Supreme Court ruled that a juror cannot be excluded from service in a capital punishment trial simply because they have personal objections to the death penalty. The court held that such exclusions could lead to biased juries favoring conviction and thus violate an individual's right to an impartial jury under the Sixth Amendment and due process clause of Fourteenth Amendment. However, jurors who stated they would automatically vote against capital punishment regardless of evidence presented could still be dismissed for cause as their views would prevent them from fulfilling their oath as jurors. This ruling significantly impacted how juries are selected in cases involving potential death sentences.

In the dissenting opinion for Witherspoon v. Illinois, the justices argued that a jury composed only of individuals who could impose capital punishment did not necessarily lead to biased or unfair outcomes. They contended that jurors' personal beliefs about the death penalty would not inherently influence their ability to objectively evaluate evidence and determine guilt or innocence. The dissenting justices also expressed concern over potential implications of this ruling on future cases, suggesting it might unduly restrict states' abilities to administer justice in accordance with their own laws and customs. Furthermore, they questioned whether excluding those opposed to capital punishment from juries was truly unconstitutional, as it could be seen as a reasonable measure taken by states seeking fair trials in serious criminal cases.