In the United States v. Wade case of 1966, the U.S Supreme Court ruled that a criminal defendant has a right to counsel at any police lineup conducted after formal charges have been filed against him or her. The decision was based on the Sixth Amendment's guarantee of legal representation for defendants in all critical stages of prosecution. In this case, Robert Wade had been identified in a lineup without his lawyer present and was later convicted based on this identification evidence. However, he appealed arguing that his constitutional rights were violated because he did not have an attorney during the lineup process. The Supreme Court agreed with Wade stating that lineups could be manipulated by law enforcement officials and therefore constituted as critical stages where legal representation is necessary to ensure fairness and protect defendants' rights.

In the dissenting opinion for United States v. Wade, Justice Harlan argued that the majority's decision to extend a right to counsel during pretrial lineups was not supported by the Sixth Amendment or any other constitutional provision. He contended that such an extension would unnecessarily complicate and hinder law enforcement procedures without significantly enhancing defendants' rights or protections. Furthermore, he disagreed with the majority's assertion that pretrial confrontations were inherently suggestive and conducive to misidentification, arguing instead that they were generally reliable means of identification subject only to normal human error. Finally, Justice Harlan expressed concern about potential practical difficulties arising from requiring counsel at all stages of criminal proceedings - including police investigations - which could impede effective law enforcement.