If a defendant in a capital case demand a trial, and it appears that more than one continuance has been granted to the State, and that the defendant has not before applied for a continuance, he shall be entitled to be admitted to bail, unless it be made to appear to the satisfaction of the court that a material witness of the State had been prevented from attendance by the procurement of the defendant or some person acting in his behalf.
Tex. Code Crim. Proc. § 29.12