NEW ORLEANS >> Lawyers for a Mississippi man who admitted killing a 12-year-old girl by shooting her four times and slitting her throat gave an appellate panel multiple reasons today to reverse his death sentence, including his belief that he was descended from space aliens.

Attorney Sarah Gannett, told a panel of three 5th U.S. Circuit Court of Appeals judges that Thomas Steven Sanders was clearly not mentally competent to stand trial when he was convicted and sentenced to death in 2014. She noted his history of brain injuries, mental illness and delusions.

Judges questioned whether Sanders displayed any signs during his trial of mental problems that showed him incompetent, noting that there was no formal motion for a declaration of incompetency by his trial attorney.

Gannett said his mental issues were brought up at trial and that the district court had an obligation to order a competency hearing, even without a formal motion. “Counsel gave the court all the information it needed,” she argued.

Prosecutors said in briefs that no concerns about Sanders’ mental capacity were addressed until the first day of trial. U.S. Justice Department attorney Vijay Shanker told the appellate panel that if the defense had concerns about Sanders’ competency they would have expressed them much earlier.

Now facing execution, Sanders was once thought to be dead. His Mississippi family had him legally declared so in 1994, after he had been missing for about seven years.

But after hunters found the body of Lexis Roberts, 12, in woods in Catahoula Parish, Louisiana, in October 2010, the investigation led to Sanders, who was arrested the next month in Gulfport, Mississippi. Investigators later found the body of the girl’s mother, Suellen Roberts, in Arizona. Sanders was arrested and tried in the kidnapping and death of the girl.

Prosecutors have said Sanders shot Suellen Roberts on a trip to a wildlife park in Arizona, and then drove Lexis Roberts to Louisiana, where he shot her four times and cut her throat.

Court records show he admitted to both killings and aided authorities in finding Suellen Roberts’ body.

Other issues in his appeal include whether he was illegally questioned after having invoked his right to an attorney. Shanker argued that a review of his interrogations showed he was eager to discuss his crimes and that his statement that he wanted to see a lawyer was, in context, not clear.

Attorneys also debated whether a potential juror in the case should have been dismissed without being asked whether she could set aside a religious-based aversion to sitting in judgment of anyone. In briefs, the defense also said that a trial prosecutor improperly suggested to jurors that Sanders might have sexually abused the girl when he alluded to unknown “horrors” the girl suffered before her death. Prosecutors said there was no reason why jurors would have speculated that that was a reference to sexual abuse.

The appellate judges — Priscilla Owen, Leslie Southwick and Andrew Oldham — gave no indication when they would rule.