Atkins v. Virginia

Those mentally retarded persons who meet the law’s requirements for criminal responsibility should be tried and punished when they commit crimes. Because of their disabilities in areas of reasoning, judgment, and control of their impulses, however, they do not act with the level of moral culpability that characterizes the most serious adult criminal conduct. Moreover, their impairments can jeopardize the *307reliability and fairness of capital proceedings against mentally retarded defendants. Presumably for these reasons, in the 13 years since we decided Penry v. Lynaugh, 492 U. S. 302 (1989),…