By Jon HerskovitzAUSTIN, Texas (Reuters) - Lawyers for Texas death row inmate Scott Panetti have launched last-minute appeals to prevent his execution set for Wednesday, arguing he suffers from schizophrenia and putting him to death would cross moral and constitutional lines.The case has drawn global attention, with the U.N. human rights experts on Tuesday calling on Texas to halt the execution. Major Texas newspapers including the Houston Chronicle and Dallas Morning News have said in editorials the execution of a person with severe mental illness would be inexcusable.Panetti, 56, was convicted of fatally shooting his wife's parents in the central Texas town of Fredericksburg in 1992. Panetti shaved his head, sawed off a shotgun and broke into the home of Joe and Amanda Alvarado, killing the two with his wife and daughter witnessing him shoot dead his mother-in-law, the Texas attorney general said.Panetti is scheduled to be executed at 1900 ET on Wednesday by lethal injection at the state's death chamber in Huntsville. If the execution goes ahead, Panetti would be the 519th person executed in Texas since the U.S. Supreme Court reinstated the death penalty in 1976, the most of any state.Lawyers for Panetti have asked the U.S. Supreme Court to halt the execution which they say would violate constitutional protections against cruel and unusual punishment. They have also asked the U.S. Fifth Circuit Court of Appeals to grant time a competency hearing, and for Texas Governor Rick Perry to issue a 30-day stay.Panetti represented himself at his capital murder trial in 1995. He wore a cowboy costume, often spoke incoherently, and tried to call more than 200 witnesses including President John F. Kennedy. He was found guilty and sentenced to death."Mr. Panetti is a sick man who has suffered from schizophrenia, an incurable mental illness, for over thirty years, including prior to and during the crime, and during his trial at which he represented himself in a floridly psychotic state," said Kathryn Kase, an attorney trying to prevent Panetti's execution.Kase said mental health experts, evangelical Christians, and former judges, prosecutors and attorneys general have said the execution would cross a moral line and serve no retributive or deterrent value.The Texas Attorney General's office has said that courts have ruled him competent to stand trial and to be executed.(Additional reporting by Stephanie Nebehay in Geneva; Editing by Mohammad Zargham)Join the conversation about this story Click here to read full news..