In Maxwell v. Powers (1994) 22 Cal.App.4th 1596, the Court held that juror affidavits were inadmissible to explain how the jury calculated its award. "The juror affidavits . . . recited the reasoning process the jury employed during deliberations to arrive at its damages figures . . . As such, the affidavits reflected the jurors' subjective mental processes and constitute inadmissible evidence to impeach a verdict. . . . 'While "jurors may testify to 'overt acts' -- that is, such statements, conduct, conditions, or events as are 'open to sight, hearing, and the other senses and thus subject to corroboration' -- they may not testify to 'the subjective reasoning processes of the individual juror . . .' " Likewise, evidence about a jury's "subjective collective mental process purporting to show how the verdict was reached" is inadmissible to impeach a jury verdict. Thus, juror declarations are inadmissible where . . . they "at most suggest 'deliberative error' in the jury's collective mental process -- confusion, misunderstanding and misinterpretation of the law." ' " ( Maxwell v. Powers, supra, 22 Cal.App.4th at pp. 1604-1605.)