Sec. 2.03 of the penal code outlines important aspects of defense in criminal prosecutions. It states that a defense to a prosecution for an offense must be clearly labeled as such, using the phrase "It is a defense to prosecution..." 

This requirement ensures that defendants are aware of the available defenses and can assert them appropriately. Furthermore, the prosecuting attorney is not obligated to prove the absence of a defense when charging the defendant. In other words, the burden of proof rests with the prosecution to establish the defendant's guilt, and they do not need to disprove the existence of a defense. The issue of whether a defense exists is typically not presented to the jury unless there is evidence supporting the defense. If the defense is presented to the jury, the court must instruct the jury that a reasonable doubt regarding the existence of the defense requires the defendant to be acquitted.

Additionally, if a defense is not clearly labeled as such in accordance with the procedural requirements, it will still be treated as a defense and subject to the same evidentiary and procedural consequences. It's essential for defendants, prosecutors, and jurors to understand the principles outlined in Sec. 2.03 to ensure that the defense process is fair and just in criminal prosecutions.

Sec. 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.

Acts 1973, 63rd Leg., p. 883, ch. 399, Sec. 1, eff. Jan. 1, 1974. Amended by Acts 1993, 73rd Leg., ch. 900, Sec. 1.01, eff. Sept. 1, 1994.