The 5th Circuit Court of Appeals has stayed the execution of Texas death row inmate Robert Campbell who was scheduled to be put to death Tuesday night.
He would have been the first inmate put to death after an Oklahoma man's botched execution brought an international outcry from death penalty opponents.
CBS News' Andrew Cohen reports that the court decided questions still lingered over Campbell's intellectual disability.
The court wrote, "Because of the unique circumstances of this case, Campbell and his attorneys have not had a fair opportunity to develop Campbell’s claim of ineligibility for the death penalty. In light of the evidence we have been shown, we believe that Campbell must be given such an opportunity."
The same court earlier ruled that Texas did not have to change its drug secrecy policy.
Robert James Campbell, 41, who is set to die for killing a 20-year-old Houston bank teller, would be the first U.S. inmate put to death since Clayton Lockett's vein collapsed during his lethal injection, prompting Oklahoma prison officials to halt the procedure. Lockett later died of a heart attack.
Oklahoma authorities have suggested the trouble started with Lockett's vein rather than the drugs, but Campbell's attorneys are among several arguing the incident demands greater execution drug transparency.
Like Oklahoma, Texas won't say where it gets its execution drugs, saying it needs to protect the producer's identity to prevent threats by death penalty opponents. Unlike Oklahoma, which used a three-drug combination in Lockett's execution, Texas uses a single dose of the sedative pentobarbital to kill inmates.
Lockett writhed and grimaced after the lethal injection was administered, and corrections officials did not realize not all the drug had entered his body for 21 minutes. Campbell's attorneys say Lockett's failed execution proves what many inmates have argued since states turned to made-to-order drugs: that the drugs put the inmates at risk of being subjected to inhumane pain and suffering.
"This is a crucial moment when Texas must recognize that death row prisoners can no longer presume safety unless full disclosure is compelled so that the courts can fully review the lethal injection drugs to be used and ensure that they are safe and legal," said attorney Maurie Levin.
Texas' attorneys say Campbell's claims are speculative and fall "far short" of demonstrating a significant risk of severe pain.
"The Constitution does not require the elimination of all risk of pain," argued Ellen Stewart-Klein, an assistant Texas attorney general.
Campbell's execution would be the eighth this year for Texas, which kills more inmates than any other state, and the fourth in recent weeks to use the compounded pentobarbital. Texas invoked confidentiality in late March when it obtained a new supply of pentobarbital to replace a stock that had reached its expiration date.
Campbell's attorneys went to the U.S. Supreme Court with last-day appeals.
The 5th U.S. Circuit Court of Appeals late Monday rejected an appeal on the drug secrecy issue, saying mere speculation wasn't enough to prove claims Campbell could be subjected to unconstitutionally cruel pain if executed with drugs from Texas' unidentified provider.
Another appeal before the 5th Circuit contends Campbell isn't mentally competent for execution because he has a 69 IQ. Courts generally set a 70 IQ as the minimum threshold. Campbell's attorneys filed a petition to the Supreme Court even before the 5th Circuit ruled on that issue.
Campbell was convicted of capital murder for the 1991 slaying of Alexandra Rendon, who was abducted while putting gas into her car, robbed, raped and shot.
"This was not a shoot and rob and run away," Rendon's cousin, Israel Santana, said. "The agony she had to go through."
Rendon, who had been making wedding plans, was buried wearing her recently purchased wedding dress.
EARLIER ON HUFFPOST:
How will Trump’s administration impact you? Learn more