Intellectual Disability, IQ Scores, and the Death Penalty

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Yesterday, the United States Supreme Court decided Hall v. Florida, a case about the death penalty and intellectual disability. It’s an important case with implications for North Carolina.

Background. In Atkins v. Virginia, 536 U.S. 304 (2002), the Court prohibited the imposition of the death penalty on mentally retarded defendants. The Court indicated that it would leave the details of the prohibition to the states, but suggested in a footnote that states should “generally conform to the clinical definitions” of mental retardation when deciding which defendants are eligible for capital punishment.

Since Atkins, the term “mental retardation” has given way to “intellectual disability.” Generally, the condition is present when, prior to age 18, an individual manifests both (1) significantly below average intellectual functioning, generally indicated by low IQ score, and (2) significant limitations in “adaptive functioning,” i.e., difficulty with everyday activities. Different states have adopted slightly different formulations of the condition, and defense attorneys have challenged the most restrictive definitions as inconsistent with Atkins and with accepted clinical practice.

Facts and procedural history of Hall. In 1978, the defendant and an accomplice raped and murdered a young woman and killed a law enforcement officer. The defendant was sentenced to death. After Atkins, the defendant alleged that his intellectual disability rendered him ineligible for execution. He offered evidence of an IQ score of 71 (and other scores, less relevant here but discussed in the Court’s opinion), as well as evidence of difficulty in adaptive functioning. The Florida Supreme Court ruled that an IQ score of 70 or below was indispensable to a claim of intellectual disability under the state’s statute, and that such a hard cutoff was constitutional. The United States Supreme Court agreed to review the case.

The majority opinion. The Court reversed, 5-4. Justice Kennedy wrote the majority opinion. He reviewed the medical community’s current approach to intellectual disability. Prominent sources such as the DSM-V allow for a diagnosis of intellectual disability even when a person’s IQ is above 70, if the person has sufficient difficulty in adaptive functioning. Further, medical experts generally view an IQ score as a range, rather than a precise figure, given the inherent measurement error in IQ tests. Justice Kennedy wrote that “[a] score of 71, for instance, is generally considered to reflect a range between 66 and 76 with 95% confidence.”

Justice Kennedy then turned to state laws, finding that “at most nine States” impose a strict cutoff like Florida’s. He reasoned that the remaining states either do not employ the death penalty or define intellectual disability more flexibly. Further, Justice Kennedy stated that the trend since Atkins has been away from a strict IQ cutoff. He viewed these facts as evidence of an emerging consensus against the use of a strict cutoff.

Finally, acknowledging that Atkins promised to give the states the power to implement its mandate, Justice Kennedy wrote that the states’ discretion was not unfettered and that Florida had overstepped its authority by adopting and unreasonably restrictive test. Ultimately, the Court concluded, “[i]ntellectual disability is a condition, not a number. . . [and] when a defendant’s IQ test score falls within the test’s acknowledged and inherent margin of error, the defendant must be able to present additional evidence of intellectual disability, including testimony regarding adaptive deficits.”

The dissent. Justice Alito wrote the dissent for the Court’s four most conservative Justices. First, he tallied the states differently than Justice Kennedy, finding that among death penalty states, about equal numbers allow consideration of measurement error in IQ tests; do not allow it; and have not addressed the issue. Thus, he saw no consensus among the states. Second, he argued that the views of “a small professional elite” – that is, the medical community – do not necessarily reflect the views of society as a whole and should not be viewed as dispositive on the Eighth Amendment issue. Third, he foresaw practical difficulties with depending on mental health professionals’ views when interpreting the Eighth Amendment: what happens if the professionals’ definition of intellectual disability changes in the future, as it has done in the past? What if the professionals disagree with one another about the proper definition? Fourth, and finally, even assuming that the medical community’s views are authoritative, Justice Alito suggested that Justice Kennedy misunderstood measurement error and had confused the two prongs of the clinical definition of intellectual disability.

Effect on North Carolina. North Carolina’s mental retardation statute is G.S. 15A-2005. It defines “significantly subaverage general intellectual functioning” as “[a]n intelligence quotient of 70 or below.” Such language is consistent with the idea of a strict cutoff. Justice Kennedy observed that “Arizona, Delaware, Kansas, North Carolina, and Washington have statutes which could be interpreted to provide a bright-line cutoff leading to the same result that Florida mandates in its cases.” However, Justice Kennedy also noted that some states’ courts have interpreted apparently strict cutoffs to allow consideration of measurement error. Our state supreme court hasn’t considered the issue. The closest it seems to have come is in State v. Locklear, 363 N.C. 438 (2009), where it simply recited the statute in the course of a discussion of the procedural requirements for determining mental retardation.

Perhaps our courts will interpret G.S. 15A-2005 in a way that is consistent with Hall. Even if they don’t find the statute amenable to such an interpretation, of course, Hall trumps the statute and capital defendants must be given the requisite leeway regarding IQ scores. The General Assembly could also weigh in, revising the statute in accordance with its understanding of Hall.

If you have additional or different thoughts about Hall and the litigation of intellectual disability claims under it, please send me an email or post a comment.

2 comments on “Intellectual Disability, IQ Scores, and the Death Penalty

  1. […] to conform the statute to the Supreme Court’s recent decisions in Hall v. Florida (summarized here) and Brumfield v. Cain (summarized here), by adding this language: “An intelligence quotient of […]

  2. […] 70 or below is used as the cutoff for intellectual disability. But in 1978, the Supreme Court overturned the death sentence of a defendant who was found guilty of rape and murder who had an IQ of 71, arguing […]

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