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The Associated Press
In this image taken from Colorado Judicial Department video, Colorado theater shooter James Holmes, top second from left in light-colored shirt, sits in court during the penalty phase of his trial, Monday, July 27, 2015, in Centennial, Colo. Dr. Jeffrey Metzner, the court-appointed psychiatrist who concluded that Holmes was legally sane when he attacked a Colorado movie theater, says Holmes' mental illness still is what caused him to kill 12 people and injure 70 others. (Colorado Judicial Department via AP, Pool)

CENTENNIAL, Colo. — More friends of James Holmes testified Tuesday about the polite, cheerful, conscientious young man they knew years before he opened fire on the audience in a Colorado movie theater.

Lori Bidwell recalled how "Jimmy" helped celebrate Halloween with them each year in California. She said he was quiet, smart, polite, and good-humored. The families went rafting together when Holmes was 21, and Bidwell recalled how he laughed and watched sea otters.

Such testimony may seem entirely irrelevant to the murders of 12 people in a suburban Denver movie theater, but the defense needs to show that even this killer was loved once, and still has people who care for him.

Bidwell counts herself among his supporters, and sat next to his parents, Arlene and Robert Holmes, after her testimony.

"When I first heard it on the news, I called because I thought this can't be possible," said Bidwell said.

A college friend also praised Holmes. Harry Soren Carr described him as introverted, but with a self-deprecating sense of humor. He didn't make fun of other people, Carr said.

Death sentences must be unanimous, and the judge has explained to jurors that their decision will be highly personal.

While Holmes was found legally sane at the time of the attack, his defense is hoping at least one juror will agree that his mental illness reduces his moral culpability so much that he deserves the mercy of a life sentence instead.

Chris Holmes, 22, became the first in her family to testify on Monday, describing their visit in jail nearly two years after the attack. She said she no longer saw the loving brother who protected her when they were growing up.

"His whole demeanor seemed different," she said. "His eyes, they were almost bugging out of his head."

But she still loves him, she said, and will still visit, and probably send him a birthday card each year in prison. "It will be up to me when my parents pass away, so I do want to do that."

Holmes' parents are expected to take the stand after sitting behind him in court every day of his 12-week trial. Robert Holmes was prepared to testify first.

Holmes' lawyers say the once-promising neuroscience student should get life without parole rather than be executed for the 12 murders. He also injured 70 others at the crowded midnight movie in July 2012.

The defense showed jurors photos of Holmes and his sister smiling during vacations to Hawaii and the California mountains. Others showed them as young children, riding bikes or hugging each other.

Chris Holmes said she grabbed her favorite photo as investigators searched the family home after the attack. It shows them as kids, grinning while flossing their teeth.

"How do you feel when you look at it now?" defense attorney Rebekka Higgs asked.

"Sad," she said, fighting tears. "Just sad."

Holmes had no visible reaction to his sister, who sat just feet from the defense table where he has been tethered to the floor.

Earlier Monday, the defense brought back the same court-appointed psychiatrist who found Holmes was legally sane during the attack.

This time, Dr. Jeffrey Metzner made a different point: that it was Holmes' severe mental illness that drove him to kill.

"Having psychosis doesn't take away your capacity to make choices. It may increase your capacity to make bad choices," Metzner testified. "He acted on his delusions, and that's a reflection of the severity of his mental illness."