In the 1972 case Chambers v. Mississippi, the U.S. Supreme Court ruled that Leon Chambers' Sixth Amendment rights were violated when he was not allowed to cross-examine a witness who had previously confessed to committing the crime for which Chambers was on trial, and when his defense could not introduce evidence of this confession at trial. The court held that these restrictions denied him a fair opportunity to defend himself against the state's charges. In its decision, it emphasized that flexible application of traditional rules of evidence is necessary in order to ensure justice and fairness in criminal trials. This ruling has been influential in shaping standards for admitting hearsay testimony and allowing defendants greater freedom in presenting their defenses.

In the dissenting opinion for Chambers v. Mississippi, Justice William O. Douglas argued that the majority's decision violated Leon Chambers' constitutional rights to a fair trial and due process of law under the Sixth and Fourteenth Amendments. He contended that by not allowing Chambers to cross-examine Gable McDonald about his prior confession or present witnesses who could corroborate this confession, the court effectively denied him an opportunity to prove his innocence. Douglas also criticized Mississippi's "voucher rule," which prevented defendants from impeaching their own witnesses, as archaic and unjust because it limited a defendant’s ability to challenge testimonies given in court against them. In conclusion, he believed that these procedural restrictions had resulted in a fundamentally unfair trial for Chambers.