Okla. Stat. tit. 22, § 22-736: Immunity from arrest and civil or criminal process

If a witness from another state comes into or passes through

this state under an order directing him to attend and testify in

this or any other state, while in this state pursuant to the order,

he shall not be subject to arrest or the service of civil or

criminal process because of any act committed prior to his arrival

in this state under the order.