In the United States v. Alphonso Vonn case of 2001, the Supreme Court ruled on whether a defendant's rights were violated if they weren't informed about their right to counsel during plea proceedings. The court held that Rule 11 does not require reversal of a conviction when there is no objection at trial and where an error in taking a guilty plea did not affect substantial rights. In this case, Vonn pleaded guilty to bank robbery but later appealed his sentence arguing that he was never told by the judge during his plea colloquy about his right to assistance of counsel if he chose to go to trial instead. However, because Vonn failed to raise this issue before entering his guilty plea or at sentencing, it was considered forfeited under Federal Rule of Criminal Procedure 52(b). Therefore, for such claims raised for the first time on appeal (as in this case), courts must apply plain-error review which requires defendants show: (1) an error; (2) that is clear or obvious; and (3) affected their substantial rights.

In the dissenting opinion for United States v. Alphonso Vonn, Justice Stevens argued that a defendant's failure to object during Rule 11 proceedings should not automatically trigger plain-error review. He contended that this approach was inconsistent with past precedent and unfairly shifted the burden of ensuring compliance with Rule 11 from the court to defendants. According to him, it is primarily the responsibility of judges, not defendants or their counsel, to ensure adherence to procedural rules in courtrooms. Therefore, he believed that if a judge fails in this duty by neglecting an essential part of Rule 11 proceedings - informing a defendant about his rights - then such error should be reviewed under harmless-error standards rather than being dismissed as "plain error". In essence, Justice Stevens disagreed with majority’s view because it seemed unjustly punitive towards defendants who may lack legal expertise and depend on courts for fair treatment.