Okla. Stat. tit. 58, § 58-61: Causes for contesting will after probate

When a will has been admitted to probate, any person interested

therein may at any time within three (3) months from the date the

will was admitted to probate contest the same or the validity of the

will. For that purpose he must file in the court in which the will

was proved a sworn petition in writing containing his allegations,

that evidence discovered since the probate of the will, the material

facts of which must be set forth, shows:

1. That a will of a later date than the one proved by the

decedent, revoking or changing the will, has been discovered, and is

offered; or

2. That some jurisdictional fact was wanting in the probate; or

3. That the testator was not competent, free from duress,

menace, fraud, or undue influence when the will allowed was made; or

4. That the will was not duly executed and attested.