"Witness" as used in this act shall include a person whose testimony is desired in any proceeding or investigation by a grand jury or in a criminal action, prosecution or proceeding.
The word "state" shall include any territory of the United States and the District of Columbia.
The word "summons" shall include a subpoena, order or other notice requiring the appearance of a witness.
Okla. Stat. tit. 22, § 721