John Errol Ferguson will add another week to the 34 years he has been on death row in Florida. The convicted mass killer was granted a stay of execution by a federal judge on Saturday.
Defense attorneys have argued for decades that Ferguson is mentally ill and that putting him to death would be "cruel and unusual punishment".
He execution was originally scheduled for Tuesday, reports AP.
"The issues raised merit full, reflective consideration," the court said when US. District Judge Daniel T. K. Hurley granted the motion for a stay.
Ferguson's attorneys told AP that the court will hear three hours of arguments on his habeas corpus petition on Friday. His lawyers are arguing that Ferguson is unfairly on death row because the court used an old and outdated definition of competency.
They contend that Ferguson is insane and that a 2007 US Supreme Court ruling prohibits the state from executing him, reports AP.
"In order for the state to execute him, Mr. Ferguson must have a rational understanding of the reason for, and effect of, his execution," Chris Handman, an attorney for Ferguson, told AP in an emailed statement.
"A man who thinks he is the immortal Prince of God and who believes he is incarcerated because of a Communist plot quite clearly has no rational understanding of the effect of his looming execution and the reason for it."
Ferguson was convicted of the July 1977 murders of six people during a home-invasion robbery, reports the Miami Herald. He was convicted separately of posing as a police officer and murdering two teenagers in January 1978.
According to the Tampa Bay Tribune, Ferguson admitted to two more murders while in jail, and it's also possible that he murdered another St. Petersburg couple in 1977.
Ferguson has had a long history with mental illness and crime. In 1971, he was declared psychotic and incompetent by a court-appointed doctor years before his first murder, reports the Tampa Bay Tribune.
"He is completely paranoid. A schizophrenic," Handman, whose law firm, Hogan Lovells, has represented Ferguson pro bono for more than 30 years, told the Miami Herald.
"When you meet him, he is deeply suspicious of your motives. He has a very tenuous grasp on reality."