Okla. Stat. tit. 12, § 2608
A. The credibility of a witness may be attacked or supported by evidence in the form of opinion or reputation, subject to these limitations:
B. Specific instances of the conduct of a witness, for the purpose of attacking or supporting his credibility, other than conviction of crime as provided in Section 609 of this Code, may not be proved by extrinsic evidence. They may, however, in the discretion of the court, if probative of truthfulness or untruthfulness, be inquired into on cross-examination of the witness if they:
Laws 1978, SB 276, c. 285, § 608, eff. October 1, 1978.