What is the test for determining whether a juror's misconduct was prejudicial?

assuming misconduct, the trial court must determine whether the misconduct was prejudicial. [Citations.]" (People v. Dorsey (1995) 34 Cal.App.4th 694, 703-704.) To determine whether misconduct occurred, "[w]e accept the trial court's credibility determinations and findings on questions of historical fact if supported by substantial evidence. [Citations.] Whether prejudice arose from juror misconduct, however, is a mixed question of law and fact subject to an appellate court's independent determination. [Citations.]" (People v. Nesler (1997) 16 Cal.4th 561, 582.)