State v. Coconino County Superior Court
In State v. Coconino County Superior Court, 139 Ariz. 422, 678 P.2d 1386 (1984), the supreme court held that the defendant who had allegedly committed acts before the effective date of a change in A.R.S. 13-502 had to be tried under the version of that statute in effect when he committed the offense. Under the former version of the statute, a defendant was presumed sane, but could rebut that presumption with evidence that "generated substantial and reasonable doubt as to his or her sanity." 139 Ariz. at 426, 678 P.2d at 1390.
The burden then shifted to the state to prove beyond a reasonable doubt that the defendant was sane. Under the amended version, however, a defendant was required to prove by clear and convincing evidence that he or she was not criminally responsible by reason of insanity.
The court in Coconino County chose not to decide the case based on the defendant's argument that applying the new version of the statute to him violated the federal prohibition against ex post facto laws. Rather, the court decided that, because "nothing in the new provisions of A.R.S. 13-502 . . . indicates a legislative intent to make the new provisions retroactive," the applicable burden of proof at the time the offense was committed was the burden to be applied in the defendant's case. 139 Ariz. at 427, 678 P.2d at 1391.