The Supreme Court established in 2002 that executing a mentally retarded person constitutes cruel and unusual punishment. (Atkins v. Virginia, 536 U.S. 304 (2002).) Twelve years later, it provided guidance in determining what constitutes mental retardation, now referred to as intellectual disability.
On May 27, 2014, the Court struck down a Florida law on intellectual disability as it relates to capital punishment. (Hall v. Florida, 572 U.S. ____ (2014).) The law provided that intellectual disability is present only when the subject has an IQ score of 70 or less. (The mean IQ score is 100.) The effect of the law was to make anyone with an IQ score of 71 or higher automatically eligible for the death penalty—people with such scores couldn’t even present additional evidence of intellectual disability.
The Court explained that the margin for error of IQ testing means that someone who scores a 71 could very well have an IQ of anywhere from 66 to 76. It also explained that, even with an IQ score above 70, people can meet the criteria for intellectual disability when one considers factors like childhood development and social functioning. So, the Court found Florida’s law irreparably flawed because it didn’t account for these issues. It also relied on the fact that Florida was in the minority because in 41 other states, a 71 IQ score, by itself, didn’t provide clearance for execution.
The result of Hall v. Florida is that states can’t use a 70 IQ score as a bright line, above which a defendant is eligible for execution. When the IQ score falls within the test’s margin of error, the defense must be able to present other evidence of intellectual disability. That means that, if 70 is the cutoff point, with a margin of error of five, a defendant who scores between 70 and 75 must have the chance to offer additional evidence.