In the case of Diamond v. Louisiana, 1963, the U.S Supreme Court was tasked with determining whether a state law that allowed non-unanimous jury verdicts in criminal cases violated the Sixth Amendment's guarantee of a fair trial. The defendant, Diamond, had been convicted by a nine-to-three vote and appealed his conviction on these grounds. However, the Supreme Court upheld his conviction and ruled that states could allow for less than unanimous verdicts in criminal trials without violating constitutional rights to due process or fair trial guarantees under the Fourteenth Amendment. This decision affirmed Louisiana’s split-verdict rule which permitted ten out of twelve jurors to agree on guilt for serious crimes except capital offenses where unanimity is required.

In the dissenting opinion for Diamond v. Louisiana, the justice argued that the majority's decision to uphold a state law requiring unanimous jury verdicts in criminal cases was flawed. The justice contended that this requirement could potentially undermine the fairness and efficiency of trials by giving undue power to a single juror who disagrees with their peers. They also expressed concern about how this rule might disproportionately affect minority defendants, as it could make it more difficult for them to secure acquittals if there is any bias among jurors. Furthermore, they pointed out that many other jurisdictions do not require unanimity in all circumstances, suggesting that such a standard is not essential for ensuring due process of law. Therefore, they believed that Louisiana should have been allowed greater flexibility in determining its own rules regarding jury decisions.