Okla. Stat. tit. 12, § 12-2606: Competency of juror as witness

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 the 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 as to any matter or statement

occurring during the course of the jury's deliberations or as to the

effect of anything upon the juror’s mind or another 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

during deliberations. A juror may testify on the question whether

extraneous prejudicial information was improperly brought to the

jury's attention or whether any outside influence was improperly

brought to bear upon any juror. An affidavit or evidence of any

statement by the juror concerning a matter about which the juror

would be precluded from testifying shall not be received for these

purposes.