Dylann Roof, a white man convicted of murdering nine African Americans during a Bible study session at church, is appealing to have his sentence overturned.

According to the New York Daily News, Roof’s lawyers have requested that his sentence be suspended until a “proper competency evaluation” can be performed. “The federal trial that resulted in his death sentence departed so far from the standard required when the government seeks the ultimate price that it cannot be affirmed,” they wrote, arguing that their client’s mental illness should have stopped him from being sent to federal death row and working as his own lawyer during a part of the trial.

Back in 2015, Roof entered Emanuel AME Church in Charleston, South Carolina and opened fire on several Black parishioners who were conducting Bible study. He fatally shot nine members of the congregation.

Felicia Sanders, a survivor of the shooting, testified in court that she told her granddaughter to play dead as the gunshots rang out. “I could feel the warm blood flowing on each side of me,” she said. “I was just waiting on my turn. Even if I got shot, I just didn’t want my granddaughter to get shot.”

During the shooting, Roof told the victims that he was killing them because Black people are “raping our women and taking over the world.”

In 2016, Roof was subsequently found guilty on 33 counts, including hate crimes resulting in death and obstruction of exercise of religion resulting in death. A few months later, he was sentenced to death, becoming the first person in the U.S. to be added to death row for a federal hate crime. In 2017, he pleaded guilty to all state charges, including nine counts of murder and three counts of attempted murder.

Oral arguments for Roof’s appeal are set for Tuesday (May 25) and will be conducted before a three-judge panel of the 4th U.S. Circuit Court of Appeals.