When is it constitutionally permissible for an appellate court to conclude that a district court's refusal to instruct the jury as to two elements of a crime constitutes harmless error?

QUESTION PRESENTED Because only a jury, acting on proof beyond a reasonable doubt, may take a person’s liberty, when, if ever, is it constitutionally permissible for an appellate court to conclude that a district court’s refusal to instruct the jury as to two elements of a crime constitutes harmless error? ii LIST OF PROCEEDINGS United States District Court Eastern District of Missouri Eastern Division No. 4:16-CR-300 (RLW) United States of America, Plaintiff, v. Mark A. Beckham, Defendant. Verdict/Order Dates: Jury Verdict: September 13, 2017 Denying Post-Trial Motion for Acquittal/New Trial: November 7, 2017 Denial of Motion for Stay: August 10, 2017 United States Court of Appeals for the Eighth Circuit United States of America, Plaintiff-Appellee v. Mark A. Beckham, Defendant-Appellant No. 18-1406 Opinion Dates: Eighth Circuit Opinion: March 8, 2019 Granting Bail Pending Appeal: May 15, 2018 Rehearing Denial: April 15, 2019