John and Roxanna Green's nine-year-old daughter, Christina-Taylor, was the youngest victim of last year's shooting in Tucson, the same spree that seriously injured Arizona Congresswoman Gabrielle Giffords.
Twenty-three-year-old Jared Loughner, the accused killer, has been declared incompetent to stand trial, and sits in prison.
"I don't think about him," Roxanna Green told "Nightline" anchor Cynthia McFadden. "I think of, that she was, like, in a car accident."
The Greens said they had not attended any of the court proceedings and had no plans to, unless their participation were needed to serve justice.
"A waste of our energy," John Green said.
Asked what their reaction would be if the incompetent-to-stand-trial ruling stood and Loughner simply remained incarcerated, the Greens said they could accept it.
"As long as he never hurts anyone ever again, and is never able to get out ... I would be O.K. with that," said Roxanna Green.
If Loughner did end up convicted of murder and executed, would the Greens take some comfort from his death?
"Not really," said John Green, who nonetheless supports the death penalty, according to Roxanna Green's new book. (She does not.) "It's not going to bring my girl back."
Loughner is never mentioned in "As Good As She Imagined," the book Roxanna Green wrote with best-selling author Jerry Jenkins, which came out Jan. 3.
The Greens met with Congresswoman Giffords and her husband, Mark Kelly, over the Thanksgiving holiday, they said. Giffords and Kelly gave the Greens' son, Dallas, a model rocket signed by Kelly, an astronaut.
"We just kind of hugged each other and supported each other and said, you know, we're all in this together," John Green said. "We wanted to make sure they didn't harbor any guilt."
"It was nice to tell her in person that, you know, we love her, we're praying for you, and we hope you get better every day," Roxanna Green said.
On the morning of the shooting, Roxanna Green said, she made sure Christina-Taylor fastened her seatbelt, then went back into the house to get a hoodie for her to wear to keep out the winter-morning chill. The hoodie was tie-dyed and had a peace sign on the back, she said.
Christina-Taylor was driven to the Giffords event -- she had an interest in politics and had volunteered for Giffords' campaign -- by a neighbor.
Roxanna Green said the neighbor's husband called her, saying he'd just gotten a call and that Roxanna needed to go to University Medical Center.
"I asked him, Did they get in a car accident? What had happened?" Roxanna Green said.
When Roxanna Green got to the hospital, the doctor told her "they tried their very best to save her but they just couldn't," she recalled, adding the doctor and the intensive-care nurses were in tears.
John Green arrived soon after, and the news left him "totally numb," he said.
President Obama met with the Greens in Tucson before the memorial service for the victims and survivors of the shooting.
"He said, 'There aren't any words, I'm so sorry,' and he gave us both a huge hug, and so did Mrs. Obama, and it just felt genuine and special," recalled Roxanna Green. "They just know, because they're parents, and they have the two lovely daughters. And it was just very comforting."
The title of Roxanna Green's book comes from a line in the speech President Obama gave in Tucson: "I want America to be as good as she imagined it."
Jared Loughner Victim Christina-Taylor Green Memorialized With Foundation
The Greens recently founded the Christina-Taylor Green Memorial Foundation, which supports academic, athletic and arts programs in Tucson schools.
"We don't want anyone to ever forget about her, because she was an amazing little girl," Roxanna Green said. "She did exceptional work in the nine years she was here, and that's what our story is about. It's an inspiring story, and it's a story of hope."
Even having grieved and memorialized their daughter so fully, John Green said "moving on" was a hard, complicated prospect.
"There's times when I'm, uh, almost afraid to move on ... or stop talking about her, because I know at some point the country is going to move on. That's why we thought it was important to tell this story, because there's going to be other tragedies in the world. ... But, right now our little girl is right on point, and people are learning things from her, so that, I guess that's a source of pride, and [there's] a sense of fear that, you know, some day that, that may go away."
Watch "Nightline" anchor Cynthia McFadden's full interview with the Greens tonight on "Nightline" at 11:35 p.m. ET