Rule 52 Harmless error and plain error

When a judge or court makes a small mistake during a criminal case, that mistake does not automatically mean you get a new trial or a different outcome. If the mistake did not seriously harm your case or change the result, the court will ignore it.

On the other hand, if a serious mistake happened during your case, the court can still fix it even if nobody pointed it out at the time. This means you do not always lose your right to challenge a big error just because your lawyer stayed quiet about it during the trial.