In the case of Carter v. Illinois, 1946, the U.S. Supreme Court ruled that a defendant's right to due process was violated when he was not informed of his right to counsel during police interrogation. The defendant, Robert Lee Carter, had been convicted for murder in an Illinois state court based on a confession obtained by police without informing him of his rights or providing access to legal representation. The Supreme Court held that this constituted a violation of the Fourteenth Amendment's Due Process Clause and reversed the conviction. This ruling emphasized that defendants must be made aware of their constitutional rights at all stages in criminal proceedings and underscored law enforcement’s responsibility in ensuring these protections are upheld.

In the dissenting opinion for Carter v. Illinois, Justice Murphy argued that the majority's decision failed to uphold an individual's constitutional right to counsel during a critical stage of prosecution. He contended that when Carter was brought before a judge and asked whether he had committed the crime, this constituted a crucial part of his trial process where legal representation should have been present. The lack thereof resulted in an unfair disadvantage for Carter who did not fully comprehend the implications of his actions at that time. Furthermore, Justice Murphy disagreed with the majority’s view on what constitutes ‘a critical stage’ in criminal proceedings; he believed it should include any point where substantial rights could be affected or lost due to absence of counsel - including preliminary hearings like identification lineups which can significantly influence case outcomes. In essence, Justice Murphy felt strongly about safeguarding defendants' Sixth Amendment rights by ensuring they are adequately represented throughout all stages of their trials.