Rule 606. Competency of juror as witness.
(a) At the trial. A member of the jury may not testify as awitness before that jury in the trial of the case in which he is sitting as ajuror. If he is called so to testify, the opposing party shall be afforded anopportunity to object out of the presence of the jury.
(b) Inquiry into validity of verdict or indictment. Upon aninquiry into the validity of a verdict or indictment, a juror may not testifyas to any matter or statement occurring during the course of the jury'sdeliberations or to the effect of anything upon his or any other juror's mindor emotions as influencing him to assent to or dissent from the verdict orindictment or concerning his mental processes in connection therewith, exceptthat a juror may testify on the question whether extraneous prejudicialinformation was improperly brought to the jury's attention or whether anyoutside influence was improperly brought to bear upon any juror. Nor may hisaffidavit or evidence of any statement by him concerning a matter about whichhe would be precluded from testifying be received for these purposes. (1983, c. 701, s. 1.)