A member of the grand jury may, however, be required by any court to disclose the testimony of a witness examined before the grand jury for the purpose of ascertaining whether it is consistent with that given by the witness before the court, or to disclose the testimony given before them by any person, upon a charge against him for perjury in giving his testimony or upon his trial therefor.
Okla. Stat. tit. 22, § 342