HOUSTON (AP) — Attorneys who contend a condemned Texas inmate set to die this week is too delusional for execution asked the U.S. Supreme Court Monday to halt his lethal injection and determine whether mentally ill people should be exempt from the death penalty because it is unconstitutionally cruel punishment.

Scott Panetti, 56, is set for lethal injection Wednesday for the 1992 shooting deaths of his in-laws at their home in Fredericksburg in the Texas Hill Country.

There was “no doubt” Panetti was severely mentally ill “before, during and after the crime for which he has been sentenced to death,” attorneys Gregory Wiercioch and Kathryn Kase told the justices. “And Mr. Panetti’s mental state has further deteriorated since his last evaluation in 2007.”

Panetti, a Hayward, Wisconsin, native, was diagnosed with schizophrenia in 1978 and had been hospitalized more than a dozen times for treatment in the decade before killing Joe and Amanda Alvarado, his estranged wife’s parents.

Justices in 2002 prohibited the execution of people who are mentally impaired, deciding it violated the Constitution’s ban on cruel and unusual punishment. But they have allowed capital punishment for mentally ill prisoners as long as the inmate has a factual and rational understanding of why he’s being put to death.

The “rational understanding” provision was added by the Supreme Court in a 2007 ruling on an appeal from Panetti. Records indicate his case has gone to the Supreme Court at least five times since his 1995 conviction and sentence.

“Imposition of the death penalty on people with severe mental illness, as with people with intellectual disability, does not serve the two goals of deterrence and retribution because of their reduced moral culpability,” Panetti’s lawyers argued to the high court Monday.