Dallas, May 13 (RHC)-- Texas is set to carry out the first U.S. execution since last month’s botched killing of a death row prisoner in Oklahoma. Robert James Campbell, a convicted rapist and murderer, is scheduled for death Tuesday evening.

As in the Oklahoma case, Texas officials have refused to reveal the source of the sedative that will be used in the lethal injection. Campbell’s attorneys have asked for a stay and the lifting of the secrecy surrounding the execution drug.

They have also accused state officials of hiding evidence that Campbell has an intellectual disability, known more commonly as mental retardation. Campbell has an IQ of 69, which falls under the standard score of 70 used to diagnose intellectual disabilities.