In which case did the Supreme Court address the validity of police lineups?

The Supreme Court addressed the validity of police lineups in the case of United States v. Wade. This landmark decision established important legal standards regarding the identification of suspects in lineups and emphasized the necessity for lineups to be conducted in a constitutionally fair manner. The ruling recognized that police lineups can potentially lead to misidentification, which can undermine the fairness of the criminal justice process.

In this case, the Court ruled that a defendant's right to counsel is violated when a lineup occurs after formal charges have been filed, and that identification procedures must be conducted with due process to ensure that witnesses are not improperly influenced. The implications of this decision are significant, as they address the potential for suggestiveness in police lineups and set forth guidelines to protect defendants' rights and ensure the reliability of witness identifications.

In contrast, the other options represent cases that primarily dealt with different legal issues such as police conduct in emergencies, juvenile death penalty, and the right to self-representation, which do not relate directly to the validity of police lineups.