Is Respondent to a Motion for a Separation of Jurors waived his right to move for a new trial when he became aware that an alternate juror had been in the jury room?

Appellant next contends that respondent waived his right to move for a new trial when he failed to move for a mistrial immediately after he became aware of the fact that the alternate juror had been in the jury room. Appellant relies on Weathers v. Kaiser Foundation Hospitals (1971) 5 Cal.3d 98, 95 Cal.Rptr. 516, 485 P.2d 1132 for the proposition that a litigant seeking a new trial on the ground of juror improprieties must present affidavits showing that neither he nor his attorney had knowledge of the misbehavior until after the verdict was returned.