Mentally retarded. Mentally impaired. Intellectually disabled. It’s hard enough to figure out what to call someone whose brain is not, for lack of a better term, “normal.” It’s even harder to determine when it’s okay to execute people with this type of disability. The U.S. Supreme Court has been struggling with this for years; so has the state of Texas, its Court of Criminal Appeals in particular. In the latest of many confrontations between the two, SCOTUS ruled on Thursday that the high court in Texas was using an outdated standard to decide who was eligible to be executed.

The decision centers around the case of Bobby J. Moore. No one doubts that in 1980 Moore, dressed in a wig and sunglasses, shot and killed supermarket clerk James McCarble in a Houston robbery. Moore’s lawyers claimed that he was intellectually disabled—with an IQ somewhere between 69 and 78—didn’t understand how to tell time or the days of the week, and couldn’t grasp concepts like addition and subtraction. Prosecutors countered that Moore knew enough to be able to shoot pool and mow lawns for money, so therefore he was competent to stand trial for capital murder.

He was convicted in 1980 and sent to death row, where he languished as his appeals wound through the courts. He seemed to be saved in 2002, when the Supreme Court handed down its landmark Atkins v. Virginia ruling, which forbade executing the “mentally retarded.” Generally the court left it up to the states to decide who fit the bill, though it noted that most courts and experts relied on three qualifiers: “sub-average intellectual functioning,” “significant limitations in adaptive skills such as communication, self-care, and self-direction,” and the presence of these two issues before age 18. The first was to be measured by IQ (mild retardation, the court noted, went from 50 to “approximately 70”) but the second was more subjective—how a person handled his or her daily living skills.

Two years later the Court of Criminal Appeals (CCA) determined seven “evidentiary factors,” now known as the Briseño factors, as guidelines for assessing a person’s “adaptive skills.” One was “Did those who knew the person best during the developmental stage…think he was mentally retarded at that time?” Another was “Has the person formulated plans and carried them through or is his conduct impulsive?” A third: “Can the person hide facts or lie effectively?” Although a trial court granted Moore relief in 2014, saying the inmate had shown—by using intellectual disability guidelines from the medical community—that he was indeed impaired, the CCA put Moore back on the execution track one year later using the Briseño factors.

The Supreme Court said it was having none of it, overturning the CCA in a 5-3 decision and sending the case back to the court. Judgments of intellectual disability should be “informed by the views of medical experts,” wrote Justice Ruth Bader Ginsburg. The justice expressed extreme skepticism of the Briseño factors, saying they “are an invention of the CCA untied to any acknowledged source” that create “an unacceptable risk that persons with intellectual disabilities will be executed.” Ginsburg gave considerable deference to the way CCA Judge Elsa Alcala, in a dissent to the 2015 decision, said that the CCA “must consult the medical community’s current views and standards in determining whether a defendant is intellectually disabled” and that “reliance on . . . standard[s] no longer employed by the medical community is constitutionally unacceptable.”

“It’s a huge change,” says defense attorney Dick Burr, who has worked on capital cases since 1979. “Texas has executed a lot of people with intellectual disabilities.” Katherine Kase, senior counsel at the Texas Defender Service, agrees. Both attorneys say there have been plenty of former death row inmates with intellectual disabilities who would still be alive if the CCA hadn’t used the Briseño factors, men like James Clark (executed in 2007), Marvin Wilson (2012), and Robert Ladd (2015). Both hope the ruling represents a chance in the way Texas determines who will be executed. “I believe the CCA will do what the Supreme Court has guided them to do,” Burr says. “Now they’ll have to look at Moore without those factors and try to apply science as it is. Courts depend on experts all the time in other contexts. There are ways to do this other than relying on seven factors based on stereotypes.”

The Moore decision could have a major impact on other death row inmates. Burr estimates that there are between ten to twenty men on death row who will be affected by the ruling. “My phone’s ringing off the hook with lawyers who say the ruling might affect their client,” Kase says. And Kase sees the Moore decision as a turning-point away from long held stereotypes. “Judges, prosecutors, defense lawyers have to be taught what intellectual disability is,” she says. “So many people think that you have to look like you have Down Syndrome or have some obvious abnormality, like not being able to speak correctly, to be intellectually disabled. But plenty of people who look normal and talk normally are intellectually impaired. We in the criminal justice system have to let go of these stereotypes. All of us.”