HUNTSVILLE, Texas — A federal appeals court halted a convicted Texas killer’s scheduled execution Tuesday so his attorneys can pursue appeals arguing he’s mentally impaired and ineligible for the death penalty.

Robert James Campbell, 41, would have been the first U.S. inmate executed since a botched execution in Oklahoma two weeks ago. He had two separate appeals, one claiming mental impairment and another that challenged the state’s plan to use a drug for which it will not reveal the source, as was the case with drugs used in Oklahoma.

“I am happy. The Lord prevailed,” Campbell said from a cell just outside the death chamber in Huntsville before being returned to death row at a prison about 45 miles to the east.

The drug secrecy issue was pending before the U.S. Supreme Court when the 5th U.S. Circuit Court of Appeals halted his punishment about 21/2 hours prior to his scheduled execution. Campbell was set to die for killing a Houston bank teller in 1991.

“Campbell and his attorneys have not had a fair opportunity to develop Campbell’s claims of ineligibility for the death penalty,” a three-judge panel of the New Orleans-based court said. “In light of the evidence we have been shown, we believe that Campbell must be given such an opportunity.”

That appeal contended Campbell wasn’t mentally competent for execution because he has a 69 IQ. Courts generally set a 70 IQ as the minimum threshold.

In 2002, the Supreme Court ruled mentally impaired people cannot be executed.

Campbell’s attorney, Rob Owen, argued Texas Department of Criminal Justice officials failed to turn over three intelligence tests from Campbell’s earlier imprisonment that bolstered his claims of mental impairment. The records had been requested 10 years ago by a previous attorney who was told they didn’t exist and only recently surfaced, he said.