How criminal defenses work in court

(1) A defense is a fact or set of facts which negatives penal liability. (2) No defense may be considered by the trier of fact unless evidence of the specified fact or facts has been presented. If such evidence is presented, then: (a) If the defense is not an affirmative defense, the defendant is entitled to an acquittal if the trier of fact finds that the evidence, when considered in the light of any contrary prosecution evidence, raises a reasonable doubt as to the defendant's guilt; or (b) If the defense is an affirmative defense, the defendant is entitled to an acquittal if the trier of fact finds that the evidence, when considered in light of any contrary prosecution evidence, proves by a preponderance of the evidence the specified fact or facts which negative penal liability. (3) A defense is an affirmative defense if: (a) It is specifically so designated by the Code or another statute; or (b) If the Code or another statute plainly requires the defendant to prove the defense by a preponderance of the evidence. [L 1972, c 9, pt of §1; am L 1973, c 136, §2(b)] COMMENTARY ON §701-115 The Code establishes two classes of defenses. As to both, it places an initial burden on the defendant to come forward with some credible evidence of facts constituting the defense, unless, of course, those facts are supplied by the prosecution's witnesses. As to the burden of persuasion, two different rules are codified. In the case of defenses which are not affirmative, the defendant need only raise a reasonable doubt as to the defendant's guilt. The other side of the coin is that the prosecution must prove beyond a reasonable doubt facts negativing the defense. The prosecution in fact does this when the jury believes its case and disbelieves the defense. In the case of affirmative defenses, the burden on the defendant increases. Now the defendant must prove by a preponderance of the evidence facts which negative the defendant's penal liability. Subsection (4) defines "affirmative defense," making it clear that this type of defense needs special legislative prescription. Unless the legislature has made a particular defense affirmative, the defendant's burden is only to raise a reasonable doubt.