WASHINGTON -- The U.S. Supreme Court on Tuesday continued a trend to limit capital punishment, ruling that Florida's IQ score cutoff was too rigid to decide which mentally disabled individuals must be spared the death penalty.
"Florida seeks to execute a man because he scored a 71 instead of 70 on an IQ test," Justice Anthony M. Kennedy wrote for the majority in a 5-4 decision.
Justice Kennedy was joined by the court's four-member liberal wing, a recurring coalition in cases concerning harsh punishments.
When the court barred the execution of people with mental disabilities in 2002 in Atkins v. Virginia, it largely let the states determine who qualified. Tuesday's decision, Justice Samuel A. Alito Jr. wrote for the four dissenters, represented a "sea change" in the court's approach.
The ruling will affect not only Florida, which has the nation's second-largest death row, but also as many as eight other states by Justice Kennedy's count, including Virginia and Alabama. They will now be required to take a less mechanical approach to mental disability in capital cases, said law professor Eric M. Freedman at New York's Hofstra University.
"Death row inmates commonly suffer from multidimensional mental problems," Mr. Freedman said. "Today's ruling requires courts to investigate these fully, by looking at the elephant rather than the tail."
The Supreme Court decision is not expected to impact Pennsylvania because the state, unlike Florida, does not have a rigid IQ test cutoff of 70 for determining whether a convict is mentally impaired.
"It doesn't really affect our law because we already recognize the standard error of measurement," said Marc Bookman, director of the Atlantic Center for Capital Representation in Philadelphia, a nonprofit death penalty resource center that serves Pennsylvania and Delaware. Pennsylvania, like most states, recognizes that the IQ score is an imprecise measurement and takes that into account in determining intellectual ability in capital cases.
In Tuesday's decision, Justice Kennedy responded that closer supervision of the states was warranted given the nature of the punishment. "The death penalty is the gravest sentence our society may impose," he wrote. "Persons facing that most severe sanction must have a fair opportunity to show that the Constitution prohibits their execution. Florida's law contravenes our nation's commitment to dignity and its duty to teach human decency as the mark of a civilized world."
The case, Hall v. Florida, arose from the 1978 murder of Karol Hurst, who was 21 and seven months' pregnant when Freddie L. Hall and an accomplice forced her into her car in a supermarket parking lot. She was found in a wooded area, where she had been beaten, sexually assaulted and shot.
There was significant evidence in school and court records of Hall's intellectual disability. Before the Supreme Court's decision in the Atkins case, a trial judge found that there was "substantial evidence" that Hall "has been mentally retarded his entire life."
After the Atkins decision, Hall challenged his death sentence, relying in part on the earlier state court determinations.
The Atkins decision gave states only general guidance. It said a finding of mental retardation required proof of three things: "subaverage intellectual functioning," meaning low IQ scores; a lack of fundamental social and practical skills; and the presence of both conditions before age 18. The court said IQ scores under "approximately 70" typically indicate retardation.
A Florida law enacted not long before the Atkins decision created what Hall's lawyers called an "inflexible bright-line cutoff" requiring proof of an IQ of 70 or lower. In 2012, the Florida Supreme Court ruled that Hall was eligible to be executed because his IQ had been measured at various times as 71, 73 and 80.
That approach, Justice Kennedy wrote, had at least two flaws. One was that it failed to take account of standard errors of measurement. "An individual's score is best understood as a range of scores on either side of the recorded scores," he wrote.
The second problem, he said, was that a rigid cutoff excludes consideration of other evidence. "Intellectual disability is a condition, not a number," he wrote.
Justice Alito protested that this changed the rules announced in Atkins, which required both low scores and more practical proof. He was also critical of the court's reliance on the views of medical experts, saying the majority had overruled part of the Atkins decision "based largely on the positions adopted by private professional organizations."
The Supreme Court assesses whether given practices are barred by the Eighth Amendment's prohibition of cruel and unusual punishment by considering, in the words of a 1958 decision, the "evolving standards of decency that mark the progress of a maturing society." In doing so, Justice Alito said, it had always "meant the standards of American society as a whole."
"Now, however," he wrote, "the court strikes down a state law based on the evolving standards of professional societies, most notably the American Psychiatric Association."
Chief Justice John G. Roberts Jr. and Justices Antonin Scalia and Clarence Thomas joined the dissent.
The majority and dissenting opinions clashed over statistics and over how many states had laws similar to Florida's. By Justice Kennedy's count, Kentucky and Virginia have adopted a fixed cutoff of 70 by statute, and Alabama by court decision. Five other states, he said, have laws open to the same interpretation.
Justices Ruth Bader Ginsburg, Stephen G. Breyer, Sonia Sotomayor and Elena Kagan joined the majority opinion. In earlier decisions limiting use of the death penalty and other harsh punishments under the Eighth Amendment, Justice Kennedy has often joined the court's liberal wing.
The court returned Hall's case to the lower courts for a fresh assessment of his condition.
Post-Gazette staff writer Torsten Ove contributed.