Texas Penal Code Sec. 2.04
Affirmative Defenses

Section 2.04 of the Texas penal code, establishes the concept of affirmative defenses in criminal prosecutions. An affirmative defense is a defense raised by the defendant that, if proven, can excuse or justify their actions, even if they would otherwise be considered criminal.
 

The key points of this law are:

1. Affirmative defenses in the Texas penal code are clearly labeled as such, stating "It is an affirmative defense to prosecution..."  The best example of this comes in the Texas self defense law.  

2. The burden of proof for affirmative defenses lies with the defendant, who must prove the defense by a preponderance of evidence. A preponderance of the evidence is greater than 50% likelihood much less than the burden of beyond a reasonable doubt that the prosecution must prove. 

3. The existence of an affirmative defense does not need to be negated by the prosecuting attorney in the accusation charging the offense.  This means the official charging documents like an information or an indictment do not need to for example say that an assault was not committed in self defense.  It must merely state that the assault was committed and it is up to the defendant to present the evidence of self defense at the trial and request a special instruction in the jury charge related to the existence of the affirmative defense of self defense.

4. The issue of the existence of an affirmative defense is not submitted to the jury unless evidence supporting the defense is admitted.  This type of evidence can be from cross examination of witnesses. 

Sec. 2.04. AFFIRMATIVE DEFENSE.

(a) An affirmative defense in this code is so labeled by the phrase: "It is an affirmative defense to prosecution . . . ."

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

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

(d) If the issue of the existence of an affirmative defense is submitted to the jury, the court shall charge that the defendant must prove the affirmative defense by a preponderance of evidence.
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.