Section 939.23 - Criminal intent(1) When criminal intent is an element of a crime in chs. 939 to 951, such intent is indicated by the term "intentionally", the phrase "with intent to", the phrase "with intent that", or some form of the verbs "know" or "believe".(2) "Know" requires only that the actor believes that the specified fact exists.(3) "Intentionally" means that the actor either has a purpose to do the thing or cause the result specified, or is aware that his or her conduct is practically certain to cause that result. In addition, except as provided in sub. (6), the actor must have knowledge of those facts which are necessary to make his or her conduct criminal and which are set forth after the word "intentionally".(4) "With intent to" or "with intent that" means that the actor either has a purpose to do the thing or cause the result specified, or is aware that his or her conduct is practically certain to cause that result.(5) Criminal intent does not require proof of knowledge of the existence or constitutionality of the section under which the actor is prosecuted or the scope or meaning of the terms used in that section.(6) Criminal intent does not require proof of knowledge of the age of a minor even though age is a material element in the crime in question.1979 c. 89; 1987 a. 332 s. 64; 1987 a. 399; 1993 a. 486. A person need not foresee or intend the specific consequences of an act in order to possess the requisite criminal intent and is presumed to intend the natural and probable consequences of the act. State v. Gould, 56 Wis. 2d 808, 202 N.W.2d 903 (1973). Instructions on intent to kill created a permissible rebuttable presumption that shifted the burden of production to the defendant, but not the burden of persuasion. Muller v. State, 94 Wis. 2d 450, 289 N.W.2d 570 (1980). The court properly refused to instruct the jury on a "mistake of fact" defense when the accused claimed that the victim moved into the path of a gunshot intended only to frighten the victim. State v. Bougneit, 97 Wis. 2d 687, 294 N.W.2d 675 (Ct. App. 1980). The constitutionality of sub. (3) is upheld. State v. Smith, 170 Wis. 2d 701, 490 N.W.2d 40 (Ct. App. 1992). The trial court's wholesale exclusion of the defendant's proffered expert and lay testimony regarding posttraumatic stress disorder from the guilt phase of a murder trial without valid justification violated the defendant's right to present a defense and to testify on her own behalf. Morgan v. Krenke, (1999).