(a) A member of the jury shall not testify as a witness before that
jury in the trial of the case in which the juror is sitting. If a juror is called to testify, the opposing party shall be afforded an opportunity to object out of the presence of the jury.
(b) Upon an inquiry into the validity of a verdict or indictment, a juror shall not testify by affidavit or otherwise nor shall a juror’s statements be received in evidence as to any matter or statement occurring during the course of the jury’s deliberations or to the effect of
anything upon the jury deliberations or any other juror’s mind or emotions as influencing the juror to assent to or dissent from the verdict or indictment or concerning the juror’s mental processes in connection therewith; provided, however, that a juror may testify on the question of whether extraneous prejudicial information was improperly brought to the juror’s attention, whether any outside influence was improperly brought to bear upon any juror, or whether there was a mistake in
entering the verdict onto the verdict form.