Okla. Stat. tit. 19 § 215.4
The district attorney, assistant district attorneys, or special assistant district attorneys authorized by subsection C of Section 215.37M of this title, shall appear in all trial courts and prosecute all actions for crime committed in the district, whether the venue is changed or not; the district attorney or assistant district attorneys shall prosecute or defend in all courts, state and federal, in any county in this state, all civil actions or proceedings in which any county in the district is interested, or a party unless representation for the county is provided pursuant to subsection A of Section 215.37M of this title; and the district attorney or assistant district attorneys shall assist the grand jury, if required, pursuant to Section 215.13 of this title. The district attorney may at all times request the assistance of district attorneys, assistant district attorneys, district attorney investigators from other districts, or any attorney employed by the District Attorneys Council who then may appear and assist in the prosecution of actions for crime or assist in investigation of crime in like manner as assistants or investigators in the district.
Okla. Stat. tit. 19, § 215.4