WHEN Bill Clinton was governor of Arkansas, he oversaw the execution of Ricky Ray Rector, a man so mentally disabled that he said he would save the pecan pie from his last meal “for later”. In 2002 the Supreme Court ruled that putting mentally retarded people to death was “cruel and unusual”, and therefore unconstitutional. But the justices left it up to the states to define what “retarded” meant, and this has proved so difficult that on March 3rd the issue came before the court again.

A Florida man named Freddie Lee Hall (pictured) was convicted in 1978, along with an accomplice, for the rape and murder of a pregnant woman and the murder of a police officer. He was sentenced to death. His lawyers are appealing that he is mentally incapacitated.

For the bulk of the hour-long hearing, the justices quizzed Seth Waxman, representing Mr Hall, and Allen Winsor, Florida’s solicitor-general, about the role of statistics in defining intellectual disability. Florida requires defendants to demonstrate both “significantly subaverage intellectual functioning” and impairments in “adaptive behaviour”, such as communicating and looking after oneself. Psychiatrists use a similar approach and, like Florida, consider an IQ score of 70 or below indicative of mental disability. But unlike many states and against the medical consensus, Florida uses 70 as a rigid cut-off point. Mr Hall’s IQ in 2002 was 71, so Florida deems him eligible to die. It refuses to consider other evidence of his disability.

That is a very slim line between prison and death, but, as Justice Sonia Sotomayor said, “A line has to be drawn somewhere.” The main question she and other justices pressed is whether Florida may ignore the “standard error of measurement” in intelligence tests. “It is universally accepted”, Mr Waxman argued, that people with “scores of 71 to 75 can and often do have mental retardation” because of a five-point margin of error. The four liberal justices, along with the swing voter, Anthony Kennedy, were inclined to agree. “Your rule prevents us from getting a better understanding of whether that IQ score is accurate or not,” Mr Kennedy admonished Mr Winsor.

Justice Stephen Breyer noted, with obvious disapproval, that Mr Hall “has been on death row for over 35 years”. Justice Kennedy asked Mr Winsor if he considered Florida’s brand of delayed justice to be “consistent with the purposes of the death penalty”. This inquiry from Mr Kennedy had nothing to do with the narrow legal question of the day, but it betrayed his more general doubts about the way the Sunshine State puts people to death.

Antonin Scalia, a conservative justice, was more hostile to Mr Hall’s defence. He noted that it took ten years after his initial conviction for Mr Hall’s lawyers to raise the issue of retardation. He added that the complexity of the crime—which involved hiding one victim’s body in a wood—belies Mr Hall’s purported disability. The state might well argue, Justice Scalia said, that Mr Hall “could not have pulled all of this off” if he was really so intellectually impaired. This is an old theme for Mr Scalia, who argued back in 2002 that the court’s bar on executing the mentally disabled would turn “the process of capital trial into a game” where murderers “feign mental retardation” to avoid the death penalty.

Justice Elena Kagan cut to the chase late in the proceedings: “Can I just ask,” she said to Mr Winsor, “why you have this policy?” Initially flummoxed, Mr Winsor replied: “Florida has an interest in ensuring that the people who evade execution because of mental retardation are people who are, in fact, mentally retarded.” Raising the IQ cutoff to 75 to take account of the margin of error, he said, “would double the number of people who are eligible for the...exemption.” In other words, Florida wants to execute more people, and therefore uses the most rigid definition of retardation that it can get away with. It might not get away with it for much longer.