In Pena-Rodriguez v. Colorado, the U.S. Supreme Court ruled in a 5-3 decision that courts must make an exception to the usual rule against jurors testifying about their deliberations if it's shown that racial bias played a part in reaching a guilty verdict. The case involved Miguel Angel Peña Rodriguez, who was convicted for unlawful sexual contact and harassment. After his trial concluded, two jurors reported that another juror had expressed racially biased sentiments during deliberations which influenced the jury’s decision-making process. The court held that where there is clear evidence of racial bias influencing jury proceedings, this undermines both the defendant's right to fair treatment and society's interest in just outcomes; thus requiring examination despite rules generally prohibiting inquiry into juror discussions post-verdict.

In the dissenting opinion for Pena-Rodriguez v. Colorado, Justice Alito, joined by Justices Thomas and Roberts, argued that the majority's decision to create a constitutional exception to the rule against jury impeachment undermines long-standing legal principles. The dissenters contended that this ruling would lead to uncertainty and instability in future cases as it is unclear how far this new principle might extend beyond racial bias. They also expressed concern about potential invasions of juror privacy and feared that post-verdict investigations could become commonplace if exceptions were made for allegations of racial bias. Furthermore, they pointed out that there are already safeguards in place during jury selection (voir dire) designed to prevent biased individuals from serving on juries.