In the 1931 case Dunn v. United States, the Supreme Court ruled on whether a defendant's constitutional rights were violated when they were not allowed to testify about their own character during a trial. The court held that while defendants have the right to present evidence of good character as part of their defense, this does not extend to allowing them to provide personal testimony regarding their own character. This decision was based on an interpretation of common law rules concerning testimonial evidence and credibility assessments by juries. The ruling clarified that it is up to witnesses who know the defendant personally - rather than defendants themselves - to give such testimony in court.

In the dissenting opinion for Dunn v. United States, Justice Stone argued that the majority's decision to overturn Dunn's conviction was incorrect because it relied on a misinterpretation of the law. He believed that there was sufficient evidence presented at trial to support a finding of guilt and disagreed with the majority’s view that certain pieces of evidence should have been excluded from consideration by the jury. According to Justice Stone, these evidences were relevant and admissible under established rules of criminal procedure. Furthermore, he contended that even if some errors occurred during trial proceedings, they did not significantly affect its outcome or deny Dunn a fair trial as required by due process clause in Fifth Amendment. Therefore, he would have upheld Dunn's conviction rather than sending case back for retrial.