In the 1971 case Moore v. Illinois, the U.S Supreme Court ruled that a criminal defendant's right to due process was violated when he was identified in court by a witness who had previously seen him only during an unnecessarily suggestive police lineup. The defendant, Charles Moore, had been convicted of armed robbery based on this identification. However, the Supreme Court found that because there were no exigent circumstances justifying such a suggestive procedure and because it carried a substantial likelihood of misidentification, its use infringed upon Moore's constitutional rights under the Fourteenth Amendment’s Due Process Clause. Therefore, his conviction was reversed and remanded for further proceedings consistent with this opinion.

In the dissenting opinion for Moore v. Illinois, Justice Brennan disagreed with the majority's decision to uphold Moore's conviction despite a violation of his Sixth Amendment right to counsel during a pretrial identification procedure. He argued that this ruling contradicted previous Supreme Court decisions which had established that such violations should result in automatic reversal of convictions, rather than being subjected to harmless error analysis. Furthermore, he contended that eyewitness identifications are notoriously unreliable and therefore any violation related to them is significant enough to warrant reversal. In addition, he expressed concern about the implications of allowing prosecutors and police officers discretion over when defendants' constitutional rights can be violated without consequence.