The testimony of any witness or witnesses admitted at a hearing on a petition to probate a will shall be recorded in one of the following methods:
If the testimony is recorded by one of the methods described in subdivisions (b) or (c), the same shall be transcribed, subscribed and sworn to by each witness, and filed with the court clerk. If the testimony is recorded by the method described in subdivision (d), the same shall be transcribed and certified by the official court reporter who took the testimony, and filed with the clerk of the court. Such evidence shall be admissible in any subsequent proceedings concerning the validity of the will, or the sufficiency of the proof if the subscribing witness is dead, or has permanently left this state.
Okla. Stat. tit. 58, § 44