In the Chapman v. California case of 1966, the U.S Supreme Court ruled that a prosecutor's comments on a defendant's decision not to testify violated their Fifth Amendment rights against self-incrimination. The court also established the "harmless error" rule, which states that some constitutional errors committed during trial do not automatically require reversal of conviction if they are deemed harmless beyond a reasonable doubt. This means that even if an error is made in trial proceedings, as long as it did not contribute to the verdict obtained and there was overwhelming evidence pointing towards guilt, then such an error can be considered 'harmless'. In this specific case involving Ruth Elizabeth Chapman and Thomas Leroy Teale who were convicted for murder in California state court, their convictions were overturned because it could not be proven beyond reasonable doubt whether or not prosecutorial misconduct contributed to their guilty verdicts.

In the dissenting opinion for Chapman et al. v. California, Justice John Marshall Harlan II argued that the majority's decision to establish a federal standard for harmless error review was an overstep of their authority and undermined state sovereignty in criminal proceedings. He contended that it is not within the Supreme Court’s jurisdiction to impose such standards on states, as they should have discretion in determining whether constitutional errors are harmless or prejudicial under their own laws and procedures. Furthermore, he expressed concern about how this ruling could potentially lead to more appeals based on technicalities rather than actual harm caused by trial errors. He believed that this would burden appellate courts with unnecessary cases and delay justice for defendants who were rightfully convicted but had minor procedural mistakes during their trials.