Did the Arizona Supreme Court err by shifting the burden of proof of harm to the defendant after a juror was exposed to inadmissible external evidence during trial?

Capital Case Did the Arizona Supreme Court err when, like a substantial number of courts throughout the country, it violated the rule contained in Court’s decisions in Mattox v. United States , 146 U.S. 140, 13 S.Ct. 50 (1892), and Remmer v. United States , 347 U.S. 227, 74 S.Ct. 450 (1954), by shifting the burden of proof of harm to the defendant even though a juror had inadmissible, external evidence during the defendant’s trial and shared it with other jurors? i