In my first year criminal law class, I teach the case Atkins v. Virginia, 536 U.S. 304 (2002), which concerns the constitutionality under the 8th Amendment of executing mentally retarded killers. A special jury trial started this week to determine whether the subject of that case, Daryl Atkins, is, in fact, mentally retarded such that he cannot be executed. See informative blog posts and links here and here. Here's an excerpt from a BBC news article cited at MindHacks:
Atkins' IQ was tested in 1998, and was found to be 59, well below the level at which a person is deemed retarded in Virginia.
But when he was retested following the Supreme Court ruling defence experts found his IQ had risen to 74, while prosecutors said it was two points higher.
Dr Evan Nelson, who tested Atkins in 1998 and 2004, wrote in a report last year that "his constant contact with the many lawyers that worked on his case" gave him more intellectual stimulation in jail than he got during childhood.
"That included practising his reading and writing skills, learning about abstract legal concepts and communicating with professionals."
But prosecutors say Atkins was never retarded in the first place, indicated by the fact that he was able to load a gun, direct the victim to a cash machine and identify a remote spot for the killing.
And here's an interesting snippet on testing for IQ when the taker has a life-or-death incentive to get a low score:
An independent forensic psychologist, Dr Bob Stinson, told the BBC it would be "unusual and unexpected" for a person's IQ to rise 17 points in seven years.
"It would be easy to deliberately do badly on one IQ test," he said.
"But it would be very difficult to feign low cognition across time, different settings and multiple examiners."
Psychology tests used to evaluate a criminal's cognition typically include sophisticated traps to catch fakers.
Difficult questions that appear to be easy may be inserted to test whether people answer correctly because they feel they can allow themselves to get a simple answer right.
Other questions that look very different, but which are actually very similar, may be used to test consistency.
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