The prosecutor of James Holmes told jurors Tuesday that once they hear from at least 12 more people this week — relatives of each of his murder victims — they will decide that death is the only appropriate sentence for his attack on a Colorado movie theater.

District Attorney George Brauchler said they will hear from "a father, a daughter, an ex-husband, a widow, a sister, a grandfather, a mom."

After weeks of testimony about the crime and about Holmes, "you will now finally get to hear from a handful of people ... to get a glimpse of who those people are who he shot to death," Brauchler said.

Holmes's defense lawyer's voice cracked as she insisted the crimes were caused by the psychotic breakdown of a mentally ill young man.

"We will ask that you not answer death with death," Rebekka Higgs said. Each of you will have to live with your decision for the rest of your lives, she added.

Even one juror's objection to capital punishment will mean life without parole for Holmes, Judge Carlos A. Samour Jr. said, but any mercy or sympathy for the defendant must be based on the evidence.

On the other hand, "no juror may make a decision for the death penalty unless the juror is convinced without a reasonable doubt that death is the appropriate sentence," the judge said.

Jurors on Monday rejected arguments that mental illness and other potential reasons for mercy outweighed factors justifying a lethal injection.

After brief opening statements for this final phase of his trial, prosecutors welcomed relatives of the murder victims to take the stand.

Among them was Tom Sullivan, whose son Alex Sullivan had been celebrating his 27th birthday and first wedding anniversary at the theater.

"He was maybe every father's dream," Sullivan said in a shaky voice. "As a man you want a son and Alex was my son and he was also my best friend."

Holmes, now convicted of murdering 12 people and trying to kill 70 more during the 2012 assault at a Batman movie, has seemed emotionless throughout the proceedings, his reactions dulled by anti-psychotic drugs.

Sandy Phillips, whose daughter Jessica Ghawi was killed, was among those prosecutors prepared to testify.

"I'm a little overwhelmed, but at the same time my job is to share Jessie with the jury, and I will do that to the best of my ability," she said outside court.

Legal experts said there's no way to predict the final sentence.

"They're making the ultimate decision of life or death, quite literally," Denver defense attorney Dan Recht said. Recht said. "All they need is one holdout ... We are far from over on this."

But former prosecutor Craig Silverman said he'd "be very surprised if the verdict was anything other than death."

"This jury is not going to want to disappoint the families of these victims," he predicted.

Holmes had been a promising scholar in a demanding neuroscience Ph.D. program at the University of Colorado until his life went awry amid the pressures of laboratory work.

He broke up with his first and only girlfriend and dropped out of school while amassing an arsenal of weapons, describing his plans in detail in a secret journal.

He self-diagnosed a litany of mental problems, and wrote that he tried to fix his brain, but failed. Then, he stood before a capacity crowd of more than 400 people, and opened fire.