Pleading insanity as a defense

16-8-103. Pleading insanity as a defense. (1) (a) The defense of insanity may only be raised by a specific plea entered at the time of arraignment; except that the court, for good cause shown, may permit the plea to be entered at any time prior to trial. The form of the plea is: Not guilty by reason of insanity; and it must be pleaded orally either by the defendant or by the defendant's counsel. A defendant who does not raise the defense as provided in this section is not permitted to rely upon insanity as a defense to the crime charged but, when charged with a crime requiring a specific intent as an element thereof, may introduce evidence of the defendant's mental condition as bearing upon the defendant's capacity to form the required specific intent. The plea of not guilty by reason of insanity includes the plea of not guilty. (b) This subsection (1) applies to offenses committed before July 1, 1995. (1.5) (a) The defense of insanity may only be raised by a specific plea entered at the time of arraignment; except that the court, for good cause shown, may permit the plea to be entered at any time prior to trial. The form of the plea is: Not guilty by reason of insanity; and it must be pleaded orally either by the defendant or by the defendant's counsel. The plea of not guilty by reason of insanity includes the plea of not guilty. (b) This subsection (1.5) applies to offenses committed on or after July 1, 1995. (2) If counsel for the defendant believes that a plea of not guilty by reason of insanity should be entered on behalf of the defendant but the defendant refuses to permit the entry of the plea, counsel may inform the court. The court shall then conduct an investigation as it deems proper, which may include the appointment of psychiatrists or forensic psychologists to assist in examining the defendant and advising the court. After its investigation, the court shall conduct a hearing to determine whether the plea should be entered. If the court finds that the entry of a plea of not guilty by reason of insanity is necessary for a just determination of the charge against the defendant, the court shall enter the plea on behalf of the defendant, and the plea entered has the same effect as though it had been voluntarily entered by the defendant. (3) If a grand jury indictment or preliminary hearing has not been held prior to the entry of the plea of not guilty by reason of insanity, the court shall hold a preliminary hearing prior to the trial of the insanity issue. If probable cause is not established, the case must be dismissed, but the court may order the district attorney to institute civil proceedings pursuant to article 65 of title 27 if it appears that the protection of the public or the accused requires a civil proceeding. (4) Before accepting a plea of not guilty by reason of insanity, the court shall advise the defendant of the effect and consequences of the plea. Source: L. 72: R&RE, p. 226, � 1. C.R.S. 1963: � 39-8-103. L. 75: (3) amended, p. 926, � 26, effective July 1. L. 95: (1) amended and (1.5) added, p. 73, � 4, effective July 1. L. 2010: (3) amended, (SB 10-175), ch. 188, p. 783, � 21, effective April 29. L. 2013: (2) amended, (SB 13-116), ch. 115, p. 393, � 2, effective August 7. L. 2025: Entire section amended, (HB 25-1058), ch. 15, p. 40, � 4, effective August 6.