The execution of a paranoid schizophrenic 64-year-old man who believes himself to be the "Prince of God" on Monday hinges on a final appeal to the Supreme Court to stay his punishment, Think Progress reported.

The National Alliance on Mental Illness, the Florida Psychiatric Society, and the Florida Psychological Association have filed a brief to the high court seeking to prevent the execution of John Errol Ferguson, arguing that Ferguson does not understand his situation, which violates the standard set in the court's ruling in Panetti v. Quarterman.

"Even putting aside Florida's unconstitutional legal standard, Florida courts assessing competency repeatedly engage in factual reasoning that is wholly unsupported by the scientific understanding of psychotic disorders," the brief states. "Review is necessary to ensure that all courts make accurate competency determinations, finding competent only those prisoners who understand the link between their crimes and their punishment."

A Florida judge ruled in October 2012 that Ferguson, who has called his impending execution a preparation for his "ascension" to immortality, may be sentenced to death despite agreeing with the medical assessment of Ferguson's condition.

"There is no evidence that Ferguson's belief as to his role in the world and what may happen to him in the afterlife is so significantly different from beliefs other Christians may hold so as to consider it a sign of insanity," Judge David Glant wrote at the time.

Though that execution was delayed by a last-minute reprieve, Gov. Rick Scott's (R) office announced on July 23 that he would indeed be put to death by lethal injection, after a federal appeals court ruled that Ferguson understood his punishment.

Ferguson, who suffered a massive brain injury when he was 21 years old, was convicted twice and sentenced to death in 1978 for his role in eight murders, two of which he committed on his own.

[Image via Agence France-Presse]