Revisiting intellectual disability and the death penalty

In 2002, in Atkins v. Virginia, the U.S. Supreme Court recognized the lesser culpability of people with intellectual disabilities and ruled that sentencing such individuals to death violated the 14th and the Eighth Amendments' prohibition against "cruel and unusual punishment."¹ The court reasoned that offenders with intellectual disabilities had significant impairments in their abilities to process information, logically reason, control their impulses and learn from experience. These factors made them both less morally culpable and more susceptible to wrongful conviction. Implementing this decision was, however, left to the states, which have taken different approaches to interpreting this ruling.²

The U.S. Supreme Court will revisit these issues this year in Hall v. Florida, which addresses whether Florida's procedure for identifying mentally retarded defendants in capital cases violates Atkins v. Virginia. Florida case law and statutes establish similar criteria to other states for the diagnosis of intellectual disability — namely, that an individual has an IQ two standard deviations below the mean; has significant impairment in adaptive behavior; and experienced the onset of his or her disability before age 18. The issue at stake is that Florida employs a bright line IQ score of 70, which means that an IQ of 71 precludes consideration of the other criteria.³

APA has filed an amicus brief in support of Hall's appeal, stating that the use of a fixed IQ score to assess intellectual function violates the professional consensus and clinical norms of mental health professionals.

In 1978, Freddie Hall and a partner were convicted of murdering a pregnant 21-year-old and a deputy sheriff. At sentencing proceedings in 1992, 10 years before Atkins, the Florida Supreme Court determined that Hall was mentally retarded. Yet, at the time of his Atkins appeal, Hall scored 71 on the WAIS-III⁴, above the rigid cut-off Florida established. This criterion is used despite the fact that the WAIS manual interprets scores in terms of confidence intervals around point scores to account for the standard error of measurement (SEM) of approximately 2.5 points, or 5 points for the suggested 95 percent confidence interval. In the range around 70, the SEM may be substantially larger due to the smaller number of people in that range of the standardization sample. Whitaker (2010) reported an SEM of 7.65 in low-IQ individuals, suggesting that a 95 percent confidence interval around a true score of 70 may extend upward to 85.⁵

Beyond the importance of the SEM in determining intellectual functioning, the Florida model for assessing intellectual disability also raises the importance of a person's adaptive functioning, which encompasses behaviors in three domains — conceptual, social and practical. Since Atkins, it could be argued that the impact of intellectual disability on adaptive functioning has come to play an even greater role in diagnosis. In fact, the Diagnostic and Statistical Manual of Mental Disorders-5 indicates that a diagnosis of intellectual disability must include an assessment of both adaptive and intellectual functioning, and that "a person with an IQ score above 70 may have such severe adaptive behavior problems … that the person's actual functioning is comparable to that of an individual with a lower IQ score."⁶ Hall, for example, is illiterate with significant impairment in his short-term memory. Florida's procedure to limit Atkins evaluations to people with IQs under 70 appears to go against standard clinical practice and norms.

On a related note, the impending Hall decision will highlight the relationship between clinical and legal definitions of mental illness and disorders, and whether states should be compelled to rely on professional definitions, or whether they can craft their own classifications.

Informed by 12 years of experience since Atkins, the court has the opportunity in Hall v. Florida to issue a ruling that may offer more specific guidance to the states, and to the mental health practitioners who provide intellectual disability evaluations in capital sentencing.

"Judicial Notebook" is a project of APA's Div. 9 (Society for the Psychological Study of Social Issues).