Lawyers are appealing to the United States Supreme Court in a last-ditch effort to stop the state of Texas from executing their client, Scott Panetti, who has been diagnosed with severe mental illness, including schizophrenia.

Defense lawyers argue that the execution of a mentally ill person, who is unable to fully grasp the sentence, violates the Eighth Amendment’s prohibition of cruel and unusual punishment.

Fifty-six-year-old Panetti, scheduled to be killed by lethal injection on Wednesday at 6:00 PM, has for 30 years been diagnosed with severe mental illness. In the six years preceding the crime for which he was convicted, he was hospitalized more than a dozen times for psychosis and delusions, according to his lawyers, who are with the Texas Defender Service.

Panetti represented himself during his 1995 trial for capital murder, during which he donned a cowboy costume and attempted to call over 200 witnesses, including John F. Kennedy and Jesus Christ.

A petition from Panetti’s sister, which has so far garnered over 90,000 signatures, states: “The trial court should never have allowed Scott to represent himself. He was clearly extremely ill… He passed up a plea deal that would have saved his life. The court could have insisted that an attorney represented my brother, but it did not, and the outcome was his death sentence.”

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The appeal to the Supreme Court, issued Monday, follows a similar request from Panetti’s lawyers to Texas Governor Rick Perry for a 30-day stay of execution after the State Board of Pardons and Paroles unanimously rejected their request for a commutation of his sentence.