Constitution of the State of Texas 1876 Art. 5, § 3. Jurisdiction of Supreme Court

(a) The Supreme Court shall exercise the judicial power of the state except as otherwise provided in this Constitution. Its jurisdiction shall be coextensive with the limits of the State and its determinations shall be final except in criminal law matters. Its appellate jurisdiction shall be final and shall extend to all cases except in criminal law matters and as otherwise provided in this Constitution or by law. The Supreme Court and the Justices thereof shall have power to issue writs of habeas corpus, as may be prescribed by law, and under such regulations as may be prescribed by law, the said courts and the Justices thereof may issue the writs of mandamus, procedendo, certiorari and such other writs, as may be necessary to enforce its jurisdiction. The Legislature may confer original jurisdiction on the Supreme Court to issue writs of quo warranto and mandamus in such cases as may be specified, except as against the Governor of the State.

(b) The Supreme Court shall also have power, upon affidavit or otherwise as by the court may be determined, to ascertain such matters of fact as may be necessary to the proper exercise of its jurisdiction.