From Chron.com: (click for full article)
In my work as the executive director of the American Association on Intellectual and Developmental Disabilities (AAIDD), I have worked with many people who have intellectual disability, formerly known as mental retardation. Most of us know people who have intellectual disability through our extended circle of friends, family, church, schools and the like. We may be familiar with the diversity of people with intellectual disability, and many have first-hand experience of some of the vast variations in how this disability appears. However, despite the variety of ways that intellectual disability may appear to a layman, it is a medical diagnosis based on clinical indications; an individual either has it, or he does not.
In 2002, when the U.S. Supreme Court categorically banned the execution of persons with (what was then known as) mental retardation in Atkins v. Virginia, the court specifically endorsed AAIDD's clinical definition of intellectual disability. Indeed, the elements of the current clinical conditions to diagnose intellectual disability have been consistent for nearly 100 years.
Yet Texas plans to execute a man named Marvin Lee Wilson next Tuesday, Aug. 7, despite an IQ score of 61 and a complete evaluation by a specialist, both of which confirm that Wilson has intellectual disability, with the specific diagnosis of mild mental retardation. Make no mistake, if a trained clinician finds that an individual has an intellectual disability, the fact that the impairment is deemed mild rather than severe does not negate nor diminish the diagnosis or its profound impact on an individual's abilities.