By Ralph Ellis and Khushbu Shah CNN

(CNN) -- A federal judge ruled Monday that Dylann Roof, convicted of killing nine people inside an African-American church in Charleston, South Carolina, is mentally competent to represent himself at the sentencing phase of his trial.

That phase is scheduled to begin Wednesday morning at 9:30 a.m. Roof could be sentenced to death.

Roof was evaluated over the weekend by Dr. James Ballenger of Charleston, a specialist in forensic psychiatry, with the results presented in court on Monday.

US District Judge Richard Gergel closed that part of the proceeding to the public, saying he wanted to protect Roof's right to a fair trial and right to self-representation.

Ballenger previously evaluated Roof in November, before Roof was found competent after a two-day hearing, Gergel's order said. But the court "felt that the serious nature of the proceedings" against Roof indicated the need for another evaluation by Ballenger "to confirm there were no material changes in his mental status" since then, the order said.

Ballenger and other witnesses testified during the daylong hearing Monday and Gergel ruled Roof "remains competent to stand trial and self-represent."

A more comprehensive opinion is expected to follow.

Roof's sentencing had been scheduled for Tuesday but he requested an additional day because he had been required to spend most of the previous days on the court's examination and competency hearing, according to the order.

A federal jury convicted Roof on December 15 of all charges stemming from the shooting at Emanuel African Methodist Episcopal Church. Roof attended a Bible study on June 17, 2015, before pulling out a pistol and killing nine people, investigators said.

Roof carefully planned the killing, investigators said, and chose the church because he wanted to start a race war. Roof is white and all his victims were black.

In a videotaped interview with detectives that was played for the jury, Roof said, "I did it."

Roof's second competency hearing was called at the request of defense lawyer David Bruck, who said he'd discovered new facts since Roof's first competency hearing.

After the first competency hearing in November, the judge sealed a document with the factual reasons behind his ruling, saying disclosure could hurt Roof's chances of a fair trial.

Some family members of victims appear torn over whether Roof should be sentenced to death.

Only three federal inmates have been executed in the United States since the federal death penalty was reinstated in 1988 after a 16-year moratorium.

Timothy McVeigh was convicted for the 1995 Oklahoma City bombing that killed 168 people. He was executed June 11, 2001. Juan Raul Garza was convicted of killing three people and running a marijuana drug ring in Texas. He was executed June 19, 2001. Louis Jones was convicted for the kidnapping and murder of 19-year-old Army Pvt. Tracie McBride. He was executed March 18, 2003.

The last person given a federal death sentence was bomber Dzhokhar Tsarnaev in 2015 after he was convicted for his role in killing four people and wounding others in the 2013 Boston Marathon, according to the Death Penalty Information Center, a Washington based nonprofit.

The US government and US military have 62 people awaiting execution, the center said.

Roof was convicted of 33 federal charges: nine counts of violating the Hate Crime Act resulting in death, three counts of violating the Hate Crime Act involving an attempt to kill, nine counts of obstruction of exercise of religion resulting in death, three counts of obstruction of exercise of religion involving an attempt to kill and use of a dangerous weapon, and nine counts of use of a firearm to commit murder during and in relation to a crime of violence.

Roof is also scheduled to be tried on state murder charges, for which he could also be sentenced to death.

CNN's Darran Simon contributed to this report.

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