Texas Penal Code - PENAL § 2.03. Defense

(a) A defense to prosecution for an offense in this code is so labeled by the phrase:  “It is a defense to prosecution . . . .”

(b) The prosecuting attorney is not required to negate the existence of a defense in the accusation charging commission of the offense.

(c) The issue of the existence of a defense is not submitted to the jury unless evidence is admitted supporting the defense.

(d) If the issue of the existence of a defense is submitted to the jury, the court shall charge that a reasonable doubt on the issue requires that the defendant be acquitted.

(e) A ground of defense in a penal law that is not plainly labeled in accordance with this chapter has the procedural and evidentiary consequences of a defense.