In the United States v. Ash case of 1972, the U.S. Supreme Court ruled that a defendant's Sixth Amendment right to counsel was not violated when an identification lineup took place after indictment but without his lawyer present. The court held that this amendment only guarantees the presence of counsel during adversarial proceedings such as trials and pretrial hearings, not investigative procedures like lineups or photo identifications conducted by police officers outside courtroom settings. Robert Ash had been convicted for robbing a D.C restaurant based on eyewitness testimony from two employees who identified him in a photographic array while he was already indicted and in jail for another offense; his attorney wasn't notified about this procedure nor present at it. His appeal argued that these circumstances breached his constitutional rights under Wade-Gilbert rule (which requires legal representation during post-indictment lineups), but SCOTUS disagreed stating those precedents didn't apply here because they were concerned with actual trials or their equivalents where prosecutorial forces are aligned against defendant.

In the dissenting opinion for United States v. Ash, Justice Brennan disagreed with the majority's conclusion that a defendant does not have a right to counsel during post-indictment photographic displays conducted by law enforcement. He argued that such an interpretation of the Sixth Amendment was too narrow and failed to consider its broader purpose: ensuring fairness in criminal proceedings. According to him, any critical stage of prosecution after formal charges are filed should involve legal representation for defendants because these stages can significantly impact their rights and outcomes at trial. In his view, photo lineups were no exception as they could potentially lead to misidentification or other forms of prejudice against defendants without them having adequate means to challenge this process or protect their interests due to lack of counsel presence.