Centennial - The prosecutor of Colorado movie theatre shooter James Holmes urged jurors on Tuesday to hear from the relatives of each of his 12 murder victims and decide that death is the only appropriate sentence for his attack three years ago.The jury is trying to decide whether Holmes, a former neuroscience student, who was convicted of murdering 12 people and trying to kill 70 more during the 2012 assault in a Colorado cinema, deserves to die or should be sentenced to life in prison without parole. The jurors on Monday rejected arguments that mental illness and other potential reasons for mercy outweighed factors justifying a lethal injection.After weeks of testimony about the crime and Holmes, District Attorney George Brauchler promised the jurors that they will finally "get a glimpse of who those people are who he shot to death".Holmes's defence 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 jnr 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.After brief opening statements, relatives began taking the stand.Among them was Tom Sullivan, whose son Alex Sullivan had been celebrating his 27th birthday and first wedding anniversary at the theatre."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."Alex's murder has left an empty spot at the dinner table, at his sister's wedding, and even in the theatre where he was killed, because the family has made a point of seeing movies there, he said."We go up and we sit in Alex's row, row 12, and we leave Alex's seat open. We sit next to him," Sullivan said, his voice wavering with emotion.Jurors have rejected arguments for mercy, but outside experts differed in their predictions of the final sentence."They're making the ultimate decision of life or death, quite literally," Denver defence attorney Dan Recht said. "All they need is one holdout ... We are far from over on this."Former prosecutor Craig Silverman countered that 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 PhD programme 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.