Egelhoff (defendant), Roberta Pavlova, and John Christenson spent the day drinking. That night, police found Christenson’s car in a ditch. Inside, Pavlova and Christenson had been shot to death, and Egelhoff was alive with gunshot residue on his hands. Egelhoff’s gun was in the floor. An hour later, Egelhoff still had a blood-alcohol content of .36 percent. Egelhoff was charged with deliberate homicide, or purposely or knowingly causing a death, under Montana law. Egelhoff claimed that his extreme intoxication made him physically incapable of committing the crime and unable to remember what happened. The jury was instructed on the requirements for a defendant to act purposefully or knowingly, but was told that it could not consider Egelhoff’s intoxication in deciding whether he had the requisite mental state. The Montana criminal code provided that a defendant’s intoxicated condition could not be considered in determining whether the defendant had the mental state required for commission of the offense. Mont. Code Ann. §45-2-203. Egelhoff was convicted. On appeal, the Supreme Court of Montana reversed the conviction, concluding that §45-2-203 violated Egelhoff’s due process right to introduce “all” evidence relevant to his mens rea. The United States Supreme Court granted certiorari.