CHICAGO >> A federal jury that convicted a former University of Illinois doctoral student of kidnapping, torturing and killing a young scholar from China now must decide if Brendt Christensen should be put to death.

While the state of Illinois, where she was killed, does not have the death penalty, the case was brought under federal law, which does allow capital punishment.

The jury returned a guilty verdict on June 24 after deliberating for less than 90 minutes, in part, because the 30-year-old Christensen’s own lawyers told jurors from the outset that he did kill 26-year-old Yingying Zhang, saying their sole objective was to persuade jurors to spare his life.

The penalty phase, which is set to start Monday, is sure to be more contentious and more emotionally grueling. Here’s a look out how it will work and how it could play out:

Q: HOW DOES IT WORK?

A: The penalty phase is a kind of mini-trial with openings, exhibits, testimony and closings. It’s expected to last at least as long as the verdict phase, around a week and a half. Deliberations over whether Christensen should live or die are almost certain to last longer. If just one juror holds out against the death penalty, he’d be sentenced to life without parole.

The form jurors must fill out at the end of deliberation has multiple sections. The first simply asks if Christensen qualifies for the death penalty because he’s over 18 and intended to kill Zhang.

Later sections are the hard parts.

A section on “aggravating factors” asks jurors, among other things, if Christensen killed Zhang “in an especially heinous, cruel, or depraved manner” and whether he’s shown no remorse. A section on “mitigation factors” asks jurors if aspects of Christensen’s “background, record or character…. mitigate against imposition of a death sentence.”

Q: WHAT ABOUT EVIDENCE?

A: The rules of evidence are looser in the penalty phase. Hearsay, opinion and emotion aren’t automatically prohibited. Zhang’s parents, for instance, are expected to testify about how their daughter’s death has devastated their own lives . They could talk about how she dreamed of becoming a crop-sciences professor.

Both parents have said they want death for Christensen. But jurors aren’t supposed to vote for a death sentence out of sympathy for or to give comfort to the family.

Q: WHAT IS THE PRIMARY QUESTION JURORS MUST ANSWER?

A: They must assess whether aggravating factors presented by prosecutors in how Christensen killed Zhang and the impact her death has had on others “sufficiently outweigh the mitigating factors,” the penalty-phase form says. If jurors decide the aggravating factors are greater, they should vote for execution. If they decide enough mitigating factors tip the scale the other way, they should opt for the life sentence.

Q: WHAT WILL PROSECUTORS SAY?

A: Jurors already heard during the verdict phase how Christensen carried Zhang into his apartment in a 6-foot duffle bag, raped, stabbed and choked her, then beat her to death with a bat and decapitated her.

Prosecutors will emphasize Christensen’s meticulous pre-planning and how he seemed proud of what he’d done. They could mention Christensen’s boast he killed 12 others before — not to suggest the claim is true but to show he has that aspiration and would continue to pose a threat, even to fellow inmates.

Prosecutors are likely to emphasize the Christensen’s high intelligence, as shown by his master’s degree in physics, arguing he had faculties to know what he did was wrong.

Q: WHAT ABOUT THE DEFENSE?

A: The defense has the bigger challenge given the grisly details jurors know from the verdict phase.

Defense lawyers are expected to tell jurors Christensen knew his homicidal fantasies months before he killed Zhang weren’t right and sought help from U of I mental health counselors. They have alleged the school didn’t do enough to help.

They are also likely to broach Christensen’s childhood and his heavy alcohol use leading up to Zhang’s slaying. They could call on friends or relatives to speak of any acts of kindness or charity by Christensen in his past.

Q: DO WE KNOW WHERE JURORS STAND ON THE DEATH PENALTY?

A: Those who categorically oppose capital punishment or believe it should be imposed on someone convicted of killing without exception can’t serve as jurors in federal death-penalty trials and were weeded out in jury selection. While jurors are supposed to strictly adhere to criteria laid out on the penalty phase form, many are likely to be hesitant about casting votes that could result in someone being put to death.

Getting 12 jurors to agree on imposing the ultimate punishment can be difficult. The life of Jodi Arias, convicted in an Arizona court for the 2008 slaying of Travis Alexander, was spared after one juror refused to vote for the death penalty after five days of deliberations.

Q: WILL CHRISTENSEN SPEAK?

A: He could. But how is a point of disagreement. The defense wants Christensen to be able to make a statement, perhaps to apologize to Zhang’s family. Prosecutors said he should only be able to speak from the witness stand and that prosecutors should be able to cross-examine him.

He may also want to reveal what he did with Zhang’s remains, which have never been found. That could be risky. He is heard on secret FBI recordings telling his girlfriend Zhang’s remains were “gone forever.” Far from crediting him for revealing how he disposed of the body, jurors could end up being more repelled.

The defense asked a judge to bar anyone from testifying that Christensen refused to help find Zhang’s remains, saying their client offered after his arrest to plead guilty and divulge where her remains were in exchange for a life sentence.

Q: WHAT ABOUT APPEALS?

A: Just because someone is sentenced to death in the federal system, doesn’t necessarily mean the person will die — at least not anytime soon. Appeals can delay executions by decades.

Since the reinstatement of the federal death penalty in 1988, 78 people were sentenced to death — but only three have actually been put to death, according to the Death Penalty Information Center data to 2018.

Federal executions are by lethal injection.