In the case of Robertson v. United States, 1951, the U.S Supreme Court was tasked with determining whether a defendant's constitutional rights were violated when he was not allowed to cross-examine a government witness about his probationary status. The defendant argued that this information could have been used to challenge the credibility of the witness and therefore should have been disclosed during trial proceedings. However, in its decision, the Supreme Court held that while defendants do generally have a right to cross-examine witnesses on matters affecting their credibility, there is no absolute rule requiring disclosure of all possible impeaching evidence prior to trial. In this particular case, it found no violation of constitutional rights because even if such questioning had been permitted and had discredited the witness somewhat in jurors' eyes; it would not likely have changed outcome given other strong evidence against him.

In the dissenting opinion for Robertson v. United States, Justice Douglas argued that the majority's decision to uphold a law allowing non-unanimous jury verdicts in federal courts was unconstitutional. He contended that this practice violated defendants' Sixth Amendment rights to a fair trial by an impartial jury and undermined the fundamental principles of our justice system. According to him, unanimous verdicts were essential because they ensured thorough deliberation and consensus among jurors before someone could be convicted of a crime. Furthermore, he believed that permitting non-unanimous verdicts would disproportionately affect minority jurors whose views might be disregarded if unanimity was not required. Thus, he disagreed with the majority's interpretation of historical precedent and constitutional text regarding this issue.