In Dunn v. Louisiana, the U.S Supreme Court examined whether a state law that allowed for non-unanimous jury verdicts in criminal cases violated the defendant's right to a fair trial under the Sixth and Fourteenth Amendments of the Constitution. The case involved Gary Duncan, who was convicted by a 9-3 jury vote for simple battery in Louisiana - one of two states allowing such verdicts at that time. In its decision, however, the court did not directly address this issue but instead remanded it back to lower courts on procedural grounds due to an error made during Duncan's initial appeal process. This left open questions about unanimity requirements in jury trials which were later addressed by other landmark decisions like Apodaca v Oregon (1972) and Ramos v Louisiana (2020).

In the dissenting opinion for Dunn v. Louisiana, it was argued that the majority's decision to uphold a conviction based on evidence obtained through an illegal search and seizure violated the Fourth Amendment rights of the defendant. The dissenting justices believed that this ruling undermined constitutional protections against unreasonable searches and seizures by law enforcement officials. They contended that allowing illegally obtained evidence to be used in court would encourage police misconduct and infringe upon individual privacy rights. Furthermore, they disagreed with the majority's assertion that excluding such evidence from trial would hinder effective law enforcement, arguing instead that upholding constitutional principles should take precedence over prosecutorial convenience or expediency.