Ill. R. Evid. 606

(a) At the Trial. A member of the jury may not testify as a witness before that jury in the trial

of the case in which the juror is sitting. If the juror is called so to testify, the opposing party shall

be afforded an opportunity to object out of the presence of the jury.

(b) Inquiry Into Validity of Verdict or Indictment. Upon an inquiry into the validity of a

verdict or indictment, a juror may not testify as to any matter or statement occurring during the

course of the jury’s deliberations or to the effect of anything upon that 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. But a juror may testify (1)

whether any extraneous prejudicial information was improperly brought to the jury’s attention, (2)

whether any outside influence was improperly brought to bear upon any juror, or (3) whether there

was a mistake in entering the verdict onto the verdict form. A juror’s affidavit or evidence of any

statement by the juror may not be received concerning a matter about which the juror would be

precluded from testifying.