WASHINGTON — The Supreme Court dismissed Alabama's bid to execute Joseph Clifton Smith, a convicted murderer found by lower courts to be intellectually disabled. The action leaves in place lower court rulings in favor of Smith, who is 55 and has spent roughly half his life on death row following his 1997 conviction for beating a man to death.

The majority to dismiss the case was formed by the three liberal justices along with Justices Brett Kavanaugh and Amy Coney Barrett. Four conservative justices dissented, saying the federal appeals court in Atlanta had improperly analyzed the case and that the Supreme Court should have ordered the appeals court to re-examine it.

The court took up Hamm v. Smith, docket number 24-872, to consider how courts should handle borderline cases of intellectual disability. Arguments in the case took place in December.

The Supreme Court ruled in 2002 that states may not execute people with intellectual disabilities. In 2014, the court held that states should consider other evidence of disability in borderline cases because of the margin of error in IQ tests, a position it reaffirmed in 2017.

An IQ score of 70 has been widely accepted as a marker of intellectual disability. Smith's five IQ tests produced scores ranging from 72 to 78, slightly above that threshold. Because his scores fell in a borderline range, the lower courts examined additional evidence of his cognitive functioning before ruling in his favor.

Smith was placed in learning-disabled classes and dropped out of school after seventh grade, his lawyers said. At the time of the crime, Smith performed math at a kindergarten level, spelled at a third-grade level and read at a fourth-grade level, according to his lawyers.