State of Arizona, Appellee v. Shawn Ryan Grell, Appellant

Summary

The court independently reviewed the evidence and held that Grell proved by a preponderance of the evidence that he had mental retardation, including significantly subaverage intellectual functioning and significant adaptive-behavior deficits arising before age eighteen. Because the Constitution prohibits executing a defendant with mental retardation, the court vacated the death sentence and imposed natural life imprisonment. The court did not reach Grell's remaining claims. Vice Chief Justice Bales, concurring, agreed with the result but noted that the trial court could have reconsidered its earlier determination in light of the additional evidence and identified unresolved procedures for later cases.