What is the test for striking out the affidavits of two jurors that impeach a jury's verdict?

The court struck out the affidavits of the two jurors upon the motion of the defendants upon the ground that they were not competent to impeach the verdict of the jury. Appellant assigns this ruling as error, claiming that the affidavits are for the purpose of establishing an independent act of irregularity and are not strictly for the purpose of impeaching the verdict. There has long been a controversy as to the soundness of the rule that jurors may not impeach their verdict. This rule and the contentions with reference thereto and the decisions of the California courts upon the subject have been carefully reviewed in Kollert v. Cundiff, 50 Cal.2d 768, 329 P.2d 897. The court there calls attention to the fact that two exceptions to the rule of exclusion have been established in California, one by Code of Civil Procedure, 657, subdivision 2, which permits the filing of affidavits to show that the verdict was the result of chance, and a second exception, established by decisions of court, to the effect that disqualifications of a juror were concealed upon his examination on voir dire. The court holds that although other situations may [175 Cal.App.2d 627] arise where, as a matter of substantial justice, other exceptions should be allowed, that nevertheless, no further exceptions should be recognized unless there is compelling reason.