In the case of McMann, Warden, et al. v. Richardson et al., 1969, the United States Supreme Court addressed whether a defendant's guilty plea could be challenged on grounds that it was made based on incompetent advice from counsel regarding potential suppression of evidence. The defendants in this case were convicted after pleading guilty to various charges and later sought habeas corpus relief arguing their pleas were induced by misrepresentation or poor legal advice about the admissibility of certain confessions they had given earlier. The court held that a voluntary plea of guilty intelligently made in light of available alternatives is not open to attack on the ground that counsel may have incorrectly appraised evidentiary issues involved in prosecution’s case against them. A defendant who pleads guilty upon competent advice from counsel need not be shown that if properly advised he might have insisted on going to trial.

In the dissenting opinion for McMann, Warden, et al. v. Richardson et al., Justice Brennan argued that a defendant's decision to plead guilty based on erroneous legal advice should not be considered voluntary and intelligent. He believed that such a plea is inherently coerced because it is influenced by misinformation about the potential consequences of going to trial. Therefore, he contended that defendants who are misled into pleading guilty should have their convictions overturned regardless of whether they were actually innocent or guilty of the charges against them. Furthermore, Justice Brennan criticized the majority's reliance on retrospective assessments of whether defendants would have been convicted had they gone to trial as irrelevant and speculative.