ATLANTA — A federal judge on Monday granted Dylann S. Roof’s request to represent himself in his hate crimes trial on charges of killing nine African-American parishioners at Emanuel African Methodist Episcopal Church in Charleston, S.C., raising the possibility that the avowed white supremacist could cross-examine survivors and family members of the deceased.

Death penalty experts predicted that Mr. Roof’s trial, a deeply somber matter in a city still recovering from the massacre, would now take on elements of farce and reveal less than some hoped about the psychological origins of Mr. Roof’s alleged rampage. By controlling his case, they said, Mr. Roof may decline to present evidence of his mental instability that his highly regarded defense team might have emphasized in both the guilt and penalty phases. Federal prosecutors are seeking to send Mr. Roof to death row, having rejected his offer to plead guilty to 33 charges in exchange for a life sentence.

Jury selection in Mr. Roof’s trial had been delayed for three weeks after his lawyers petitioned Judge Richard M. Gergel of Federal District Court in Charleston to declare him incompetent to stand trial. A two-day hearing on that question was closed, but it now seems likely that Mr. Roof’s relationship with his legal team broke down over its desire to present evidence related to his mental state.

On Friday, having studied a court-ordered psychiatric evaluation, Judge Gergel ruled that Mr. Roof was competent. The standard for competency is low under federal law, merely a determination that the defendant is not suffering from a mental defect that renders him unable to assist in his defense or understand the consequences of the case.