The Supreme Court unanimously decided Tuesday that mentally ill death row inmates should not receive unlimited suspensions of their post-conviction challenges.
The nation's highest court decided that such suspensions make sense on a case-by-case basis, but should be left to the discretion of individual judges, and not be automatic.
The court offered its ruling based on arguments from two death penalty cases. One concerned Sean Carter, who has been diagnosed as schizophrenic, and the other Ernest Gonzales, who suffers from psychosis, AFP reported.
Their lawyers had invoked their clients' mental health to get procedures against them frozen until they can become competent to participate in their own defense.
Writing for the court, conservative Justice Clarence Thomas wrote that lawyers were "quite capable" of defending their clients without their help.
The ruling overturned decisions by lower courts in Ohio and Arizona, respectively, granting unlimited stays of execution for the two men.
Carter was sentenced to death for the rape and murder of his adoptive grandmother, while Gonzales was sent to death row for stabbing a couple in front of their seven-year-old child during a robbery.
In both cases, the states of Ohio and Arizona, supported by the federal government, appealed to Supreme Court to protest against the lack of a time limit on the suspensions, once given.
In its ruling, the court also reversed a 1967 decision in which it had frozen the death sentence of a mentally deficient man without giving a timeframe. The inmate ended up dying in prison.
In 2002, in its "Atkins v. Virginia" decision, the Supreme Court forbid the execution of people with intellectual disabilities, because their handicap could increase the risk of an arbitrary execution.
But it left it to individual states to determine what constitutes a mental handicap.
In 2012, Texas defied international protest to execute two inmates suffering from mental health troubles. A third prisoner, in Georgia, was saved at the last minute because of a change in the procedure for lethal injection.