The Supreme Court took the unusual step on Thursday of dismissing a case that it had already heard, handing a rare win to a death-row prisoner and avoiding a ruling that could make it harder for other prisoners with intellectual disabilities to avoid execution.In rare cases, the justices agree to hear a case, only to conclude later that it would be inappropriate or unnecessary for the high court to decide the case. When this happens, the court can decline to rule for either side and instead hold that the case is “dismissed as improvidently granted.” For brevity’s sake, most observers typically say these cases were “DIG’d.”The court does not typically announce the vote breakdown when DIG-ing a case. Thanks to the concurring and dissenting opinions, it can be readily inferred this time. Chief Justice John Roberts and Justices Clarence Thomas, Samuel Alito, and Neil Gorsuch all dissented from the court’s move. Logically, that means Justices Brett Kavanaugh and Amy Coney Barrett joined with the court’s liberals to nix the case.In a concurring opinion, Justice Sonia Sotomayor applauded the court’s decision to avoid a ruling. “Here, neither Alabama nor the United States seriously contends that the District Court’s finding was clearly erroneous,” she explained in a concurring opinion joined by Justice Ketanji Brown Jackson. “For good reason: It was not.” Alito argued in dissent that the lower courts had misapplied precedents on executing people with intellectual disabilities and criticized his colleagues for not clarifying them. “By instead remaining silent, the Court exacerbates the confusion that plagues our jurisprudence in this area,” he claimed.Thursday’s decision is good news for Joseph Smith, the death-row inmate in this particular case. Since the Supreme Court issued no actual ruling, the lower court decision where he prevailed is the final word. An Alabama jury convicted him of murdering Durk Van Dam in 1997 in a dispute over money. After receiving a death sentence from the trial court, Smith and his lawyers challenged the death sentence in court by claiming that he was intellectually disabled. They pointed to IQ tests where he scored in the mid-to-high 70s, as well as other evidence of his poor educational performances and low mental aptitudes.It is a long-standing principle of the Anglo-American legal system that people with mental illnesses and intellectual disabilities are less culpable for their crimes. Lord Blackstone, the famed eighteenth-century judge and legal commentator, noted in the parlance of his era that “idiots and lunatics are not chargeable for their own acts, if committed when under these incapacities: no, not even for treason itself.” He invoked a Latin legal maxim that, translated into English, meant “Madness alone punishes the madman.”In 2002, the Supreme Court held in Atkins v. Virginia that the Eighth Amendment’s ban on cruel and unusual punishment includes executing people with intellectual disabilities. Using an Eighth Amendment test that it had applied since the 1950s, the court looked at whether there was a national consensus against executing people with intellectual disabilities and concluded that one existed. (More on that test later.)“Those mentally retarded persons who meet the law’s requirements for criminal responsibility should be tried and punished when they commit crimes,” Justice John Paul Stevens wrote for the court, using the parlance of his time. “Because of their disabilities in areas of reasoning, judgment, and control of their impulses, however, they do not act with the level of moral culpability that characterizes the most serious adult criminal conduct. Moreover, their impairments can jeopardize the reliability and fairness of capital proceedings against mentally retarded defendants.”The Atkins ruling did not specify the level of intellectual disability that could be permitted for an execution, nor did it spell out how to discern when someone met the constitutional threshold. Some death penalty states responded to Atkins by enacting a bright-line cutoff, typically at an IQ of 70. In 2014, the Supreme Court weighed in again by ruling that Florida could not execute a man whose IQ score had ranged between 71 and 80. This time, the court held that defendants must provide additional evidence of intellectual disability in “borderline” cases.In this particular case, Smith took two tests from two experts, one hired by his own lawyers and one hired by the state. He scored a 74 on his lawyers’ test and a 78 on the one administered by Alabama. Both tests had a confidence interval of 95 percent, meaning that his score could fall between 70 and 83. The two experts, as well as a third one also hired by Smith’s lawyers, reached different conclusions.