Art. 4.18. CLAIM OF UNDERAGE    

(b) The motion must be filed and presented to the presiding judge of the court:

(1) if the defendant enters a plea of guilty or no contest, before the plea;

(2) if the defendant's guilt or punishment is tried or determined by a jury, before selection of the jury begins; or

(3) if the defendant's guilt is tried by the court, before the first witness is sworn.

(c) Unless the motion is not contested, the presiding judge shall promptly conduct a hearing without a jury and rule on the motion. The party making the motion has the burden of establishing by a preponderance of the evidence those facts necessary for the motion to prevail.

(d) A person may not contest the jurisdiction of the court on the ground that the juvenile court has exclusive jurisdiction if:

(1) the person does not file a motion within the time requirements of this article; or

(2) the presiding judge finds under Subsection (c) that a motion made under this article does not prevail.

(e) An appellate court may review a trial court's determination under this article, if otherwise authorized by law, only after conviction in the trial court.

(f) A court that finds that it lacks jurisdiction over a case because exclusive jurisdiction is in the juvenile court shall transfer the case to the juvenile court as provided by Section 51.08, Family Code.

(g) This article does not apply to a claim of a defect or error in a discretionary transfer proceeding in juvenile court. A defendant may appeal a defect or error only as provided by Article 44.47.