Judge Grady Jolly of the 5th U.S. Circuit Court of Appeals in New Orleans says the three-judge panel determined that medical records and sworn affidavits of Simon's lawyers and a sworn affidavit of a clinical neuropsychologist raised substantial questions about whether the death row inmate suffered a neurological injury when he fell in prison in January.
His attorneys claimed the fall left Simon unable to recognize them or to discuss his case.
Simon was sentenced to death for the 1990 slaying of members of a Quitman County family. The execution was blocked hours before its scheduled time Tuesday.