When jurors left a courtroom in Charleston, S.C., on Thursday to deliberate on the nearly three dozen counts facing Dylann Roof, the question was not what they would decide but how swiftly.

Before Roof, 22, entered court for opening statements in his federal hate-crime trial last week, there was essentially no question of his guilt in the slayings of nine parishioners inside the Mother Emanuel AME Church last year. This point was hammered home during six days of harrowing testimony: Prosecutors played video footage of Roof, a self-avowed white supremacist, admitting his guilt to FBI agents, and they cited Roof’s own writings about wanting to start a race war. An attorney for Roof did not dispute the facts outlined by prosecutors, saying, “We don’t disagree with any of this.”

Jurors wound up needing about two hours Thursday to convict Roof on all counts. Although that outcome was widely expected, it remains far less clear what will happen in the next portion of the trial, when the focus shifts to whether Roof will be sentenced to death.

With Roof’s guilt all but uncontested, his potential sentence has been the case’s looming uncertainty. The federal trial will resume Jan. 3, when the same jurors return to the courtroom, about a mile from the church, to begin the penalty phase.

During this part of the trial, attorneys typically try to outline two different sets of factors for the jurors. Prosecutors will argue the aggravating factors, which are anything that would support the imposition of a death sentence; defense attorneys, meanwhile, offer mitigating factors that would suggest life imprisonment.

Dylann Roof, wearing shackles, is escorted into a vehicle in Charleston, S.C., after he was found guilty. (Matt Walsh/State newspaper via AP)

The Justice Department is seeking a death sentence for 18 of the 33 counts Roof was convicted of Thursday — all of the counts of obstruction of exercise of religion by force resulting in death and the counts of using a firearm to commit murder during a crime of violence.

In a court filing earlier this year, prosecutors outlined a series of what they described as aggravating factors, offering a preview of what they will likely argue in court. They detailed the lengths of planning that went into the attack, said Roof intentionally killed more than one person in a single incident and noted that three of the victims were between ages 70 and 87. (The federal death penalty statute notes that a young or old victim can be seen as particularly vulnerable.)

How Roof will respond during this next phase is one of the trial’s other mysteries. He has been represented by a group that includes David Bruck, who has extensive experience with death-penalty cases, but Roof has said that he wants to represent himself during the penalty portion of the trial. He reiterated this stance Thursday after he was found guilty.

Felicia Sanders, who survived the church massacre and watched her son Tywanza Sanders die, smiles while speaking to media after Roof was found guilty. (Matt Walsh/State newspaper via AP)

One mitigating factor that can be used to argue for life in prison is whether a defendant has an impairment. Bruck had previously indicated in a court filing he would be raising the issue of Roof’s mental state during the penalty phase.

Bruck wrote earlier this year that he would “introduce expert evidence relating to a mental disease or defect or any other mental condition bearing on the issue of punishment.”

Bruck and others will remain as Roof’s standby counsel during the penalty phase, but it is not clear whether he will get to address the jury again — or how much of his strategy will be abandoned by Roof. (Bruck has told The Washington Post that he will not comment on the case.)

During his closing arguments Thursday, Bruck appeared to be doing his best to hint at this line of thinking, asking jurors to consider what Roof was thinking and casting doubts on the 22-year-old’s mental competence.

“Why did Roof do this?” Bruck asked. “Why was he motivated?”

He described Roof as an immature young man given over to a “mad idea” and fueled by beliefs absorbed online, and he pointed to Roof’s inability to remember how many victims he had shot, saying that Roof suffers from an inability to perceive the world as it is.

John Pinckney, center, father of church shooting victim the Rev. Clementa Pinckney, leaves the courthouse after the guilty verdicts Thursday. (Randall Hill/Reuters)

“Consider the mad energy, the rationale, the senselessness,” Bruck said as the prosecution mounted objection after objection. “The fact that one is a racist does not tell you what else is going on. And what else is going on is what you should be thinking about.”

If Roof is sentenced to death, he would be the first person to join the federal death row since Dzhokhar Tsarnaev was given a death sentence last year for the Boston Marathon bombing, in 2013. There are a number of similarities between the two cases, both of which involved young men whose guilt was not contested by attorneys who instead focused on trying to obtain a life sentence. (Bruck, Roof’s attorney, was also on Tsarnaev’s legal team.)

The Justice Department announced its decision to seek a rare federal death sentence for Roof about a year after winning one for Tsarnaev in Boston. The decision in Charleston is not unanimously supported by all of the relatives of the victims, and prosecutors rejected offers by Roof’s attorneys who said he would plead guilty in exchange for a sentence of life in prison. (Roof is also set to stand trial early next year in state court on charges of murder and attempted murder for the church massacre, and he faces a possible death sentence there as well.)

Federal death sentences are extremely unusual. Since the federal death penalty statute was reinstated in 1988, the government has gone to trial seeking such sentences about 200 times, according to the Federal Death Penalty Resource Counsel Project. And in such cases, juries have opted in favor of life in prison far more than they have death sentences, picking life imprisonment about twice as often.

Roof’s trial is unfolding at a moment when executions and death sentences alike have both plummeted nationwide, and public support for capital punishment has steadily fallen from a peak about two decades ago.

It is also unclear whether the government would be able to carry out its fourth execution since 1988, and its first federal execution since 2003, when Gulf War veteran Louis Jones Jr. was put to death for kidnapping, raping and murdering Tracie Joy McBride, a 19-year-old Army recruit. The most famous federal inmate put to death, Timothy McVeigh, was executed in 2001 for the Oklahoma City bombing.

Federal officials said last year after Tsarnaev’s sentencing that the government did not have any lethal injection drugs, which are increasingly difficult for officials to obtain amid an ongoing shortage. While a spokesman did not directly respond last month when asked whether the Bureau of Prisons has any drugs, officials said last year they did not have any because of an ongoing review of the federal death penalty. That review is still underway.

Dustin Waters in Charleston, S.C., contributed to this report.

Further reading:

Dylann Roof wanted his attorneys for the guilt part of the trial, not the penalty portion

From 2015: How a jury decided to sentence the Boston Marathon bomber to death