Hamm v. Smith · ¶112

In modern parlance, one had to be “severely” or “profoundly” mentally retarded to be a common-law idiot. Penry, 492 U. S., at 333. Psychiatrists recognize “four degrees of mental retardation: mild, moderate, severe, and profound.” Smith, 213 So. 3d, at 248–249, and n. 3. “ `Mild' mental retardation,” Atkins explained, “is typically used to describe people with an IQ level of 50–55 to approximately 70.” 536 U. S., at 308, n. 3. People within this category “know the difference between right and wrong and are competent to stand trial.” Id., at 318. “Moderate” describes those whose IQs are 35–40 to 50–55. Smith, 213 So. 3d, at 249, n. 3. “Severe” describes those whose IQs are 20–25 to 35–40. Ibid. And “profound” describes those whose IQs are below 20 or 25. Ibid. This Court has explained that common-law idiots generally had IQs around 25, making them severely or profoundly mentally…

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