Scott Panetti, 45, was scheduled to receive a lethal injection late Thursday for killing two of his in-laws in 1992 but a federal judge stayed the execution to give the trial judge 60 days to consider whether the inmate is mentally competent.
Defense attorney Michael Gross said Panetti believes he's being executed "because of this conspiracy out there to prevent him from preaching the gospel."
In a 1986 decision the U.S. Supreme Court banned the execution of the mentally ill unless they understand the reason for, or reality, of their pending punishment.
Panetti had been hospitalized with mental illness 14 times before the double murder. He defended himself during the trial, dressed in a cowboy costume.
The National Mental Health Association urged Gov. Rick Perry to commute Panetti's death sentence because it says mental illness can influence actions at the time of the crime and "compromise" their competence during trial.