(a) Upon an inquiry into the validity of a verdict, no evidence may be received to show the effect of any statement, conduct, event, or condition upon the mind of a juror or concerning the mental processes by which the verdict was determined.
(b) The limitations in subsection (a) do not bar evidence concerning whether the verdict was reached by lot.
(c) After the jury has dispersed, the testimony of a juror may be received to impeach the verdict of the jury on which he served, subject to the limitations in subsection (a), only when it concerns:
(1) Matters not in evidence which came to the attention of one or more jurors under circumstances which would violate the defendant's constitutional right to confront the witnesses against him; or
(2) Bribery, intimidation, or attempted bribery or intimidation of a juror. (1977, c. 711, s. 1.)