What is the role of a reviewing court in determining bias in the presentation of evidence?

The " 'trial court has both the duty and the discretion to control the conduct of the trial' [citation] 'the Due Process Clause clearly requires a "fair trial in a fair tribunal," [citation], before a judge with no actual bias against the defendant or interest in the outcome of his particular case. [Citations.]' [Citation.] The role of a reviewing court 'is not to determine whether the trial judge's conduct left something to be desired, or even whether some comments would have been better left unsaid. Rather, we must determine whether the judge's behavior was so prejudicial that it denied [the defendant] a fair, as opposed to a perfect, trial. [Citation.]' [Citation.] In deciding whether a trial court has manifested bias in the presentation of evidence, we have said that such a violation occurs only where the judge ' "officiously and unnecessarily usurp[ed] the duties of the prosecutor . . . and in so doing create[d] the impression that he [was] allying himself with

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the prosecution." ' [Citation.]" (People v. Harris (2005) 37 Cal.4th 310, 346-347 (Harris).)