Tex. Rev. Civ. Stat. art. 4015c

In any investigation or prosecution under any provision of this chapter, the court or tribunal in which the same is pending may compel any person to attend and give testimony, and to produce such papers, books and documents as may be desired by the State. No person shall be exempt from giving testimony therein, but no criminal action or proceeding shall be brought or prosecuted against such witness on account of any testimony so given or furnished by him.