Okla. Stat. tit. 58, § 58-43: Witnesses on trial of contest - Depositions

If the will is contested, all the subscribing witnesses who are

present in the county, and who are of sound mind, must be produced

and examined; and the death, absence or insanity of any of them must

be satisfactorily shown to the court. If none of the subscribing

witnesses reside in the county, and are not present at the time

appointed for proving the will, or although such witnesses reside in

the county and are insane or incompetent, and such facts are first

made to appear to the court, either in contested or noncontested

will cases, the court may admit the testimony of other witnesses to

prove the sanity of the testator and the execution of the will and,

as evidence of the execution, it may admit proof of the handwriting

of the testator and of the subscribing witnesses, or any of them.

Provided that when the testimony of any nonresident witness or

witnesses residing out of the county wherein any will is sought to

be admitted to probate, may be desired, touching the execution of

such will, either in contested or noncontested will cases, it shall

be lawful for the party seeking to have such will admitted to

probate, or resisting the same in the district court, to cause the

deposition of such witness to be taken in like manner, as now is or

hereafter may be provided in civil cases; and the court may, in its

discretion, direct the original of such will to be attached to any

commission issued in such case; and the deposition of any such

witness taken, certified and returned, according to law, shall be of

like force and effect as if his testimony had been heard in the

court; provided, that before any such original will shall be

suffered to be attached to any such commission, a photostatic or

certified copy thereof shall be made and examined, and certified by

the judge to be a true copy of the original, and until the return of

such original, such copy shall be retained in the office of the

judge, in lieu of such original will; and if such will be admitted

to probate, the same may, in case of the loss or destruction of the

original thereof, be recorded from such certified copy. Provided,

further, that in all cases where wills have heretofore been proved

in substantial compliance with the provisions hereof, such proof is

hereby validated.