Henderson v. United States, 568 U.S. 266 (2013), was a United States Supreme Court case in which the Court held regardless of whether a legal question was settled or unsettled at the time of trial, an error is "plain" within the meaning of Rule 52(b) of Federal Rule of Criminal Procedure so long as the error was plain at the time of appellate review.

[1] Armarcion D. Henderson pleaded guilty to possessing a firearm while being a felon; a federal violation.

[3] While the appeal was pending, this Court decided in Tapia v. United States that it is an error for a court to "impose or lengthen a prison sentence to enable an offender to complete a treatment program or otherwise to promote rehabilitation.

"[4] While this meant that the District Court's sentence was erroneous, the Fifth Circuit determined that Rule 52(b) did not give it authority to correct the error.

[1] Justice Scalia wrote a dissenting opinion in which he argued that an issue of law that is unsettled at the time of the trial cannot be considered "plain error" for the purposes of appellate review.