Texas Statutes
Article 24.29. Uniform Act to Secure Rendition of Prisoners in Criminal Proceedings
Section 9. Exemption From Arrest and Service of Process

Sec. 9. EXEMPTION FROM ARREST AND SERVICE OF 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 another state, while in this state pursuant to the order he is not 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.