Okla. Stat. tit. 22, § 22-724: Exemption from arrest and service of process

If a person comes into this state in obedience to a summons

directing him to attend and testify in this state he shall not while

in this state pursuant to such summons be subject to arrest or the

service of process, civil or criminal, in connection with matters

which arose before his entrance into this state under the summons.

If a person passes through this state while going to another

state in obedience to a summons to attend and testify in that state

or while returning therefrom, he shall not while so passing through

this state be subject to arrest or the service of process, civil or

criminal, in connection with matters which arose before his entrance

into this state under the summons.