What is the test for determining whether jury tampering or jury misconduct prejudiced the jurors?

The question whether jury tampering or jury misconduct prejudiced the jurors is a mixed question of law and fact subject to an appellate court's independent determination. (People v. Danks, supra, 32 Cal.4th at p. 303.) However, an appellate court accepts the "trial court's credibility determinations and findings on questions of historical fact if supported by substantial evidence." (Id. at p. 304, citation and quotation marks omitted.) The "presumption of prejudice may be rebutted, inter alia, by a reviewing court's determination, upon examination of the entire record, that there is no substantial likelihood that the complaining party suffered actual bias." (Id. at p. 303, citation and quotation marks omitted.)