Thomson Reuters
The alleged gunman, 22-year-old Dylann Roof, was deemed mentally competent to stand trial for hate crimes in South Carolina, US District Judge Richard Gergel ruled last week.
The test for competency is whether the defendant "has a sufficient present ability to consult with his lawyer with a reasonable degree of rational understanding" and "has a rational as well as factual understanding of the proceedings against him," according to Gergel's ruling.
Roof, who faces 33 federal charges and the death penalty, was an avowed racist. A disturbing website registered to Roof - with a racist manifesto and dozens of photos of the alleged attacker posing with guns and the Confederate flag - was found shortly after the massacre occurred.
Jury selection for Roof's trial was delayed after his defense attorneys called for a competency test. It will resume on Monday.
Police say Roof sat with the Wednesday night bible study group for at least an hour debating whether or not to shoot "because everyone was so nice to him," NBC reported last year.
He ultimately decided he "had to go through with his mission," he confessed to law-enforcement officials shortly after he was arrested.