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 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 with an IQ in the 70s, was sentenced to die 36 years ago for killing a store clerk during a robbery. In 2014 Mr Moore had his death sentence revoked after successfully making a claim under Atkins v Virginia, a ruling of 2002 banning the execution of intellectually disabled people. But a year later the Texas Court of Criminal Appeals (CCA) sent him back to death row. The quarrel in Moore v Texas is whether the CCA used the right standard when it decided that Mr Moore—who at 13 could name neither the days of the week nor the months of the year, nor distinguish between addition and subtraction—is too clever to qualify for an exemption.

Clifford Sloan, Mr Moore’s lawyer, argued that Texas’s “unique approach” to measuring intellectual disability relies on “harmful and inappropriate lay stereotypes” which are “anti-clinical” and contradict the “core holding” in Atkins. In response, Scott Keller, the Texas solicitor-general, noted that the justices largely left it to the states to decide who qualifies as mentally retarded, or, in today’s parlance, “intellectually disabled”. The CCA, Mr Keller maintained, dutifully applied the three-part test endorsed in Atkins: low IQ, deficits in “adaptive functioning” and onset before the age of 18. The Texas court could not be faulted, he said, for turning to one psychological manual rather than another to flesh out the first two parts.

Mr Sloan’s rejoinder to this claim was embraced by the four liberal justices and, it seems, by Justice Anthony Kennedy, the fifth vote Mr Moore needs to avoid execution. In Hall v Florida, a case from 2014, the Supreme Court ruled that standards for intellectual disability must be “informed by the medical community’s diagnostic framework”, and may not disregard established medical practice. But in evaluating Mr Moore’s case, Mr Sloan noted, the Texas appeals court bashed the district court for relying on the current manual of the American Association on Intellectual and Developmental Disabilities. Instead, the CCA flipped back to an old standard from 1992, plus a list of seven factors springing, apparently, from the minds of the judges. None of the factors (including whether the person “can lie effectively” or “formulate plans”) included a single citation.

Justices Stephen Breyer, Elena Kagan and Sonia Sotomayor zeroed in on the CCA’s comment that as intellectual disability standards are “exceedingly subjective”, they should be geared not to clinical standards but to the “level and degree of mental retardation at which a consensus of Texas citizens would agree that a person should be exempted from the death penalty.” This idea alarmed Mr Breyer. The will of the people of Texas, he said, “has nothing to do with it.” Standards for intellectual disability should be fashioned from the views of medical professionals, he implied, even if a rule that works for all 50 states is hard to come by.

Ms Sotomayor pressed Mr Keller to defend the CCA’s reliance on Steinbeck’s character to define who counts as intellectually disabled. One problem with fashioning standards after Lennie, Ms Sotomayor pointed out, is that the character seems just as capable as Mr Moore, who, as a teenager, made money cutting grass. “Lennie was working on a farm. How is that different from mowing a lawn?” And if Mr Moore’s ability to hide weapons and lie disqualifies him from being intellectually disabled, why should Lennie be included? He sought to “hide the death of the rabbit he killed”, Ms Sotomayor recalled, and yet he was held up by the Texas court as “not just mildly, but severely disabled”.

Mr Keller tried to explain away the Lennie reference as a mere “aside” in a ruling that was otherwise consistent with both Atkins and Hall. But a majority of the justices seem sceptical that Texas’s standards for measuring intellectual disability jibe with their precedents. Word on Mr Moore’s fate should arrive in the spring.