Wisconsin Statutes & Annotations
Chapter 971 - Criminal procedure — proceedings before and at trial.
971.15 - Mental responsibility of defendant.

971.15 Mental responsibility of defendant.
(1) A person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect the person lacked substantial capacity either to appreciate the wrongfulness of his or her conduct or conform his or her conduct to the requirements of law.
(2) As used in this chapter, the terms “mental disease or defect" do not include an abnormality manifested only by repeated criminal or otherwise antisocial conduct.
(3) Mental disease or defect excluding responsibility is an affirmative defense which the defendant must establish to a reasonable certainty by the greater weight of the credible evidence.
History: 1993 a. 486.
It is not a violation of due process to put the burden of the affirmative defense of mental disease or defect on the defendant. State v. Hebard, 50 Wis. 2d 408, 184 N.W.2d 156 (1971).
Psychomotor epilepsy may be legally classified as a mental disease or defect. Sprague v. State, 52 Wis. 2d 89, 187 N.W.2d 784 (1971).
The state does not have to produce evidence contradicting an insanity defense. The burden is on the defendant. Gibson v. State, 55 Wis. 2d 110, 197 N.W.2d 813 (1972).
A voluntarily drugged condition is not a form of insanity that can constitute a mental defect or disease. Medical testimony cannot be used both on the issue of guilt to prove lack of intent and also to prove insanity. Gibson v. State, 55 Wis. 2d 110, 197 N.W.2d 813 (1972).
The legislature, in enacting the ALI Institute definition of insanity as this section, deliberately and positively excluded “antisocial conduct" from the statutory definition of “mental disease or defect." Simpson v. State, 62 Wis. 2d 605, 215 N.W.2d 435 (1974).
The jury was not obliged to accept the testimony of two medical witnesses, although the state did not present medical testimony, because it was the jury's responsibility to determine the weight and credibility of the medical testimony. Pautz v. State, 64 Wis. 2d 469, 219 N.W.2d 327 (1974).
The court properly directed the verdict against the defendant on the issue of mental disease or defect. State v. Leach, 124 Wis. 2d 648, 370 N.W.2d 240 (1985).
Discussing use of expert evidence of personality dysfunction in the guilt phase of a criminal trial. State v. Morgan, 195 Wis. 2d 388, 536 N.W.2d 425 (Ct. App. 1995), 93-2611.
When a defendant requests an 11th-hour change to a not guilty by reason of mental disease or defect plea, the defendant has the burden of showing why the change is appropriate. There must be an offer of proof encompassing the elements of the defense and a showing of why the plea was not entered earlier. State v. Oswald, 2000 WI App 3, 232 Wis. 2d 103, 606 N.W.2d 238, 97-1219.
A court is not required to conduct an on-the-record colloquy with respect to a defendant's desire to abandon a not guilty by reason of mental disease or defect plea. Only fundamental constitutional rights warrant this special protection, and such a plea falls outside the realm of fundamental rights. State v. Francis, 2005 WI App 161, 285 Wis. 2d 451, 701 N.W.2d 632, 04-1360.
A court is not required to inform a defendant during a plea colloquy that the defendant may plead guilty to a crime and still have a jury trial on the issue of mental responsibility. Because neither the federal or state constitutions confers a right to an insanity defense, a court has no obligation to personally address a defendant in regard to the withdrawal of a not guilty by reason of mental disease or defect plea, although it is the better practice to do so. State v. Burton, 2013 WI 61, 349 Wis. 2d 1, 832 N.W.2d 611, 11-0450.
Although expert testimony may be helpful to a defendant in the responsibility phase of the trial, a favorable expert opinion is not an indispensable prerequisite to a finding of mental disease or defect. Although expert testimony is not required, it is highly unlikely that a defendant's own testimony, standing alone, will be sufficient to satisfy the burden of proof. State v. Magett, 2014 WI 67, 355 Wis. 2d 617, 850 N.W.2d 42, 10-1639.
Because every person is competent to be a witness under s. 906.01 and there is no exception in s. 906.01 for defendants who have entered a plea of not guilty by reason of mental disease or defect, a defendant is competent to testify to the defendant's own mental health at the responsibility phase of a trial. This does not mean, however, that the defendant's testimony alone is sufficient to raise a question for the jury. State v. Magett, 2014 WI 67, 355 Wis. 2d 617, 850 N.W.2d 42, 10-1639.
Consumption of prescription medication cannot give rise to a mental defect that would sustain an insanity defense. Furthermore, it is established law that one who mixes prescription medication with alcohol is responsible for any resulting mental state. State v. Anderson, 2014 WI 93, 357 Wis. 2d 337, 851 N.W.2d 760, 11-1467.
Although a better practice, a circuit court is not required to conduct a right-to-testify colloquy at the responsibility phase of a bifurcated trial resulting from a plea of not guilty by reason of mental disease or defect. State v. Lagrone, 2016 WI 26, 368 Wis. 2d 1, 878 N.W.2d 636, 13-1424.
The Power of the Psychiatric Excuse. Halleck. 53 MLR 229 (1970).
The Insanity Defense: Conceptual Confusion and the Erosion of Fairness. MacBain. 67 MLR 1 (1983).
Criminal Law—First Degree Murder—Evidence of Diminished Capacity Inadmissible to Show Lack of Intent. Gertig. 1976 WLR 623.

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