(CNN) The white nationalist convicted of killing nine people at a historically black church in Charleston, South Carolina, believed his prison sentence was irrelevant because he would be freed after a coming race war, his attorneys said in a filing appealing his conviction and death sentence on Tuesday.
"When Dylann Roof represented himself at his capital trial, he was a 22-year-old, ninth-grade dropout diagnosed with schizophrenia-spectrum disorder, autism, anxiety, and depression, who believed his sentence didn't matter because white nationalists would free him from prison after an impending race war," the filing says.
The argument about Roof's mental stability came as his attorneys asked a federal appeals court to overturn his 2017 death penalty conviction for the 2015 massacre at Mother Emanuel AME Church.
In a 321-page motion filed with the 4th US Circuit Court of Appeals, the attorneys wrote that the federal trial court "clearly erred in finding Roof competent to stand trial and sentencing, and it violated his due process rights by holding inadequate competency hearings."
The attorneys argued that Roof was allowed to represent himself at his capital trial despite being mentally incompetent and "disconnected from reality."
The trial court, the attorneys said, was in a "rush to move the case along" and prevented the jurors from hearing evidence surrounding Roof's competency hearings in which five experts found him to be "delusional."
"Roof's crime was tragic, but this Court can have no confidence in the jury's verdict," the attorneys wrote.
Roof, an avowed white supremacist, was convicted of federal murder and hate crimes charges, and he was sentenced to death in January 2017. He represented himself at the penalty phase of the trial, telling jurors that "there's nothing wrong with me psychologically" and to disregard his attorneys' previous arguments during the trial.
"Anything you heard from my lawyers in the last phase, I ask you to forget it," he said.
Prosecutors presented evidence in court of chilling writings from a jailhouse journal he wrote after the attack.
"I would like to make it crystal clear. I do not regret what I did," Roof wrote in the journal. "I am not sorry. I have not shed a tear for the innocent people I killed."
Roof's mental state was explored in detail in documents from Roof's competency hearings and videos of three prison visits by his family that were released in May 2017. According to one transcript, Roof told a psychologist working for his defense team that his death penalty wouldn't be carried out because he'd "be rescued by white nationalists after they took over the government."
After his conviction on federal charges, Roof pleaded guilty in April 2017 to state murder and attempted murder charges in the killings. He was sentenced to nine consecutive life sentences and three consecutive 30-year sentences for those counts.
The federal government has not executed a convict since 2003. Attorney General Bill Barr directed the Bureau of Prisons to reinstate the federal death penalty last July, but the Supreme Court agreed to put that plan on hold in December.