Did the Mississippi Supreme Court establish an erroneous legal standard when it held that proof of intellectual disability in Atkins cases requires a showing of 'adaptive functioning deficits ... so severe that [the petitioner] should be ruled intellectually disabled,' when the term 'so severe' does not appear in the diagnostic criteria, and in light of this Court's holding that Atkins decisions must be 'informed by the work of medical experts'?

QUESTION PRESENTED Did the Mississippi Supreme Court establish an erroneous legal standard when it held that proof of intellectual disability in Atkins cases requires a showing of “adaptive functioning deficits ... so severe that [the petitioner] should be ruled intellectually disabled,” when the term “so severe” does not appear in the diagnostic criteria, and in light of this Court’s holding that Atkins decisions must be “informed by the work of medical experts”? ii