[JURIST] The US Supreme Court [official website] ruled [opinion, PDF] on Tuesday that a Florida law permitting the death penalty for criminal defendants whose IQ is greater than 70 violates the Eighth Amendment [text] of the US Constitution. The case, Hall v. Florida [SCOTUSblog backgrounder] involved a defendant who was sentenced to death for killing a pregnant woman and a sheriff’s deputy in 1978. Hall scored a 71 on a state-given IQ test, making him eligible for the death penalty under Florida law, even though his lawyers claimed that Hall was mentally disabled. Writing for the majority, Justice Anthony Kennedy announced that a defendant whose IQ is close to the 70-point cutoff has the right to present additional testimony of his or her mental disability:

[W]hen 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. …. By failing to take into account the standard error of measurement, Florida’s law not only contradicts the test’s own design but also bars an essential part of a sentencing court’s inquiry into adaptive functioning.

Justice Samuel Alito filed a dissent, which was joined by Chief Justice John Roberts and Justices Antonin Scalia and Clarence Thomas.

The death penalty [JURIST news archive] has been a highly controversial issue, especially with regard to individuals with mental disabilities. In January the Supreme Court of India [official website] commuted the death sentences [JURIST report] of two individuals on the basis of mental illness. In August 2012 JURIST guest columnist Laura Kagel opined [JURIST op-ed] that Georgia’s standards for mental disability [JURIST report] in death penalty cases are a “perversion of justice.” In July 2012 JURIST guest columnist Terrica Ganzy argued [JURIST op-ed] that Warren Hill, a Georgia man who allegedly had a mental disability, was improperly sentenced to death and that Georgia should adopt a “preponderance of evidence” standard for mentally disabled claims in capital offense cases.