State of Arizona v. Stephen Jay Malone Jr

JUSTICE TIMMER, opinion of the Court:

¶1 Although a defendant cannot use evidence of a mental disease or defect to show he did not form a crime's requisite mental state (mens rea), see State v. Mott , 187 Ariz. 536 , 541, 931 P.2d 1046 , 1051 (1997) ; State v. Schantz , 98 Ariz. 200 , 212-13, 403 P.2d 521 , 529-30 (1965), he may use evidence of a character trait for impulsivity to cast doubt on the existence of premeditation, see State v. Christensen , 129 Ariz. 32 , 35, 628 P.2d 580 , 583 (1981), which forms part of the mens rea for first degree murder under A.R.S. § 13-1105(A)(1), see State…