Plain Error. A reviewing court may grant relief for “plain error” even if the error was not raised and preserved at trial or sentencing. In an appeal based on “plain error,” the defendant must show: (1) there was an error (2) that is “clear or obvious,” and (3) affected the defendant's “substantial rights.” To determine if a ruling affected the defendant's substantial rights, an appellate court analyzes the alleged error in the context of the entire record. Even if the defendant can satisfy these three requirements, relief is only available if the court determines that the error “seriously affect[ed] the fairness, integrity, or public reputation of judicial proceedings.” Rights or objections that were waived will not be reviewed for “plain error,” but those that were merely “forfeited” may be reviewed.

Appellate courts are more likely to find plain error if the error at trial affected the defendant's constitutional rights. Courts frequently find plain error occurred through incorrect jury instructions, improper admission of evidence, errors in sentencing, a change in law between trial and appeal, or prosecutorial misconduct. Most circuits have allowed plain error claims on other bases as well.

A court is unlikely to find plain error where the defense counsel contributed to the error, where the error concerned a fact admitted by the defendant, where the defendant failed to request curative instructions at trial, where curative instructions were given to correct the error, or where evidence against the defendant was overwhelming.