FANS of “Of Mice and Men”, the 1937 novella by John Steinbeck, will recall the character of Lennie Small, an oafish, dim-witted man whose physical strength is ill matched to his love of rabbits. On November 29th, in a remarkable example of law imitating art, a hearing at the Supreme Court will put Lennie back in the spotlight. The question is whether the fictional man’s intellectual profile should help determine the fate of Bobby Moore, a real-life Texan awaiting execution.

Mr Moore, a man of limited intellectual capacity, was sentenced to death in 1980 after killing a grocery store clerk during a bungled burglary in Houston, Texas. Aged twenty at the time, Mr Moore had not enjoyed a happy or productive childhood. He failed first grade—twice—and was promoted to second grade only to “keep him with children of a similar age”. Subsequent years remained a struggle. Mr Moore, unable to keep up with the lessons, was often relegated to drawing pictures while other students were doing classwork. He endured taunts of “stupid” from classmates, teachers and his own father. In fifth grade, a racially charged incident on a school bus left Mr Moore with gashes in his face and head that may have caused brain damage and exacerbated his deficits. He failed every subject in ninth grade and dropped out of high school. Disgusted, Mr Moore’s father sent the teenager packing, telling him to leave the house for good.

In the wake of Atkins v Virginia, a Supreme Court ruling from 2002, Mr Moore’s lawyers challenged his death sentence. In Atkins, the justices had determined, by a 6-3 vote, that executing “mentally retarded” individuals amounts to “the needless imposition of pain and suffering” in violation of the 8th Amendment bar on “cruel and unusual punishments”. In 2014, Mr Moore was removed from death row after a judge concluded, based on expert testimony, that his mental impairment qualified him for exemption under Atkins. But a panel of judges at the Texas Court of Criminal Appeals reversed that ruling a year later. In consulting the “definition of intellectual disability presently used by the AAIDD [American Association on Intellectual and Developmental Disabilities]”, Judge Cheryl Johnson wrote, the trial court had mistakenly used a newfangled standard.

Since Atkins leaves it up to the states to decide who counts as intellectually disabled, Ms Johnson noted, and since the Texas legislature had not weighed in, the rule in the Lone Star state should be traced back to a 1992 standard the court had relied upon in Ex Parte Briseño, a 2004 ruling. According to this definition, which the court suggested was based upon the character in Mr Steinbeck’s novel, neither a low IQ nor a deficit in “adaptive behaviour” qualifies an individual as intellectually disabled unless the latter is directly traceable to the former. “Most Texas citizens might agree that Steinbeck's Lennie should, by virtue of his lack of reasoning ability and adaptive skills, be exempt”, Judge Cathy Cochran wrote. But lawbreakers who are less impaired than the fictional farmhand, she suggested, should not be released from "an otherwise constitutional penalty".

In Ms Johnson's estimation, Mr Moore showed plenty of signs of basic intelligence. He “took it upon himself to earn money from the neighbours and then used the money to buy food” for his siblings, she noted. In committing his crime, he showed the ability to “hide facts” and “lie effectively in his own interest”. And he “doggedly pursued his desire to obtain new appellate counsel” after his conviction in 1980. So despite his IQ scores hovering in the low 70s, Ms Johnson concluded, Mr Moore does not meet the Texas standard for intellectual disability. He is “a person capable of functioning adequately in his everyday world with intellectual understanding and moral appreciation of his behaviour”.

This assured assessment of Mr Moore’s ability to carry out basic life functions is starkly at odds with the professional judgment of a psychologist who reviewed his file. And the judge’s casual observations about Mr Moore bear little relationship to updated, unanimously agreed upon standards of intellectual disability. In an amicus brief, the American Psychological Association (APA) identifies several problems with Texas’s regime. First, Ms Johnson “refus[ed] to recognise...diagnostic advances” in clinical standards since 1992, turning a blind eye to more recent diagnostic manuals with updated definitions. Second, the Texas criminal court ignored the Supreme Court’s 2014 decision in Hall v Florida, which eliminated Florida’s IQ score cutoff of 70; Mr Moore’s IQ score “between 69 and 79” is, by itself, “sufficient...to diagnose significant limitations in intellectual functioning”. And Ms Johnson's armchair observations about Mr Moore’s capacities, the APA argued, are “unsupported by any scientific or medical evidence and inconsistent with the...standards used by mental health professionals”. In short, behavioural deficits and compromised intelligence—not complete incompetence—are the hallmarks of people with intellectual disabilities.

In a shifting political climate where respect for scientific consensus is no longer a sure bet, Texas maintains that it can choose from a range of standards for intellectual disability, including one drawn from the pages of a novel. Next week, the Supreme Court will probe whether the state is justified in putting people to death based on ideas that are disavowed by mental health professionals—and used nowhere else in America.