D was president and general manager of Prime, Inc., a trucking company. D and his fourteen-year-old stepson together with several friends arranged a hunting trip to Creede, Colorado. After a hunter's safety class, D drove all night to be in Creede at the agreed time. On the trip up the mountain road, D became increasingly anxious and apprehensive and had feelings of unreality. He began to notice that the trees surrounding the road had a particular type of bark that was 'soft and unnatural.' He was paranoid and questioned his stepson about what was occurring and why he was being 'tricked.' D stopped his pickup truck. When their companions stopped their truck to make sure everything was all right, D demanded that all of the individuals kneel in prayer with him. Kim testified that he had never known D to be 'a religious person.' After the prayer, D insisted that Roller drive Shane to the campsite in Kim's truck and that Kim drive D's truck with D as a passenger. Kim complied because D appeared to be tired from his trip from Missouri. D began to speculate on whether he was alive or dead. At the campsite, D was convinced that he was dead and had gone to hell. While resting D concluded that he was a corpse in a mausoleum and that it was necessary to redeem himself in order to get to heaven. He referred to pitching his tent to raising a temple. He called a member of the party the devil and eventually went for his gun. The other hunters realized by this time that D was disturbed and took the rifle from him. D then unbuckled his hunting knife, went to his tent, and stabbed A.D. in the upper back. He was immediately subdued. D repeatedly called his tent a temple, and that he was acting in an irrational and 'crazy' manner. The victim suffered serious injuries and was taken to a hospital. D then tried to stab himself when Kim attempted to take the hunting knife away from him, but Kim disarmed him. D returned to his truck, removed a can of kerosene from the truck bed, and went into the partially erected tent. He poured kerosene on the floor, sat in a folding chair, and ignited the tent while he was still inside of it. Kim grabbed a gun and ammunition and took Shane into the woods to avoid a further confrontation until help arrived. D left the tent shortly before it was burned completely and fell asleep on the ground. He then returned to the cabin and lay down. The police arrived and arrested D. For several months, D had ingested forty to fifty 'HOLD' cough drops a day. On the trip, D did not sleep and consumed approximately one hundred twenty cough drops within a twenty-four-hour period. Prior to the attack, D had never felt any adverse or intoxicating effects from the cough drops. A Dr. Lewis gave an expert opinion that there was very little doubt that the dextromethorphan caused a psychotic disorder known as 'organic delusional syndrome' or 'toxic psychosis.' Symptoms include a distorted perception of reality, paranoia, auditory hallucinations, and delusions. Dr. Lewis concluded that D was psychotic and delusional at the time he attacked McCowan. Dr. Lewis testified that D was incapable of distinguishing right from wrong at the time of the alleged assault and that D did not have the ability to formulate the specific intent to commit a criminal act. D entered a plea of not guilty and waived his right to a jury trial. Both the prosecution and the court were advised that D was not entering a plea of not guilty by reason of insanity and elected not to plead the affirmative defense of impaired mental condition. D gave a notice of defenses to the court and to P. The affirmative defense of involuntary intoxication was raised in the notice. D claimed that the warning on the cough drop box did not alert the defendant to the danger of intoxication. The judge found that D committed serious injuries with a deadly weapon but did not rule on the issue of involuntarily intoxication. The trial judge acquitted D because the prosecution 'failed to prove an element of the offense or any lesser included offense; namely, the culpability element of mens rea.' P appealed. The question before us is whether the failure of the defendant to plead the defense of insanity or impaired mental condition precludes the introduction of evidence of insanity or impaired mental condition to establish the absence of mens rea.