June 30, 2011 -- Late one May night in 1983, Diane Downs sped into an emergency room dropoff in Springfield, Ore., with a horrifying story to tell.
Her three small children, Christie, 8; Cheryl, 7; and Danny, 3, were inside her blood-soaked car, shot at close range.
In the frantic scene, hospital employees quickly determined that Cheryl was already dead and that Christie and Danny were clinging to life.
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Downs had also been shot, in the left forearm, though her wound was not life threatening.
When police arrived at the scene, Downs, 27 at the time, told them a bizarre story of being flagged down by a bushy-haired stranger on a dark and deserted country road.
Det. Doug Welch remembers getting the call for what would turn out to be his first homicide investigation. He responded to McKenzie-Willamette Hospital and immediately interviewed Downs, a postal worker.
"Her initial statement was that she had taken the kids out to a friend's house," said Welch. "And it grew dark and upon their return home she decided to -- to do some sightseeing. And she took a deserted country road with three sleeping kids in her car.
"And along this road, off to the side, out stepped a man who flagged her down. She stopped the car and asked him what he wanted. And his response was, 'I want your car.' She replied, 'You've got to be kidding,' at which time he pushed her aside and reached in and shot the sleeping kids."
Downs said she then faked throwing her keys to divert the gunman's attention, pushed him out of the way, jumped back in her car and raced to the hospital with her badly wounded children. She says it was during the struggle with the stranger that she was shot in the arm.
Police Tell Public to Be on Lookout
Fearing there could be a gun-wielding killer on the loose, police released information to the public to be on the lookout.
But suspicions of Downs herself quickly began to surface.
"There were a number of things which didn't make sense, even that first night," Welch said. "Sightseeing when it's pitch black out? And why are the kids fatally or near-fatally wounded, and she, being right-handed, is shot in the left arm? I mean, think about it. She's the biggest threat to him, not three sleeping children."
Diane Downs Gives Bizarre Interviews
Within a month of the shootings, with her two surviving children still in the hospital, Downs began giving a series of bizarre interviews to the media.
"She couldn't keep her mouth shut," Welch said. "She talked all the time. In a sense, Diane was her own worst enemy."
While police increasingly suspected Downs, she adamantly denied any involvement when speaking to the media.
"Why would I have taken my kids to the hospital?" she said in an interview. "Wouldn't I have made sure they were dead and then cried crocodile tears? That's insane to think that I would do such a thing and then bring the witnesses in against myself -- that's crazy."
Anne Jaeger was a local reporter for KEZI in Eugene, Ore., at the time. She remembers Downs' demeanor in her interviews as peculiar.
"People would see little sound bites of her talking on television, and I think they started getting the feeling that there's something really wrong with this person," Jaeger said.
Although police had found spent .22 caliber bullet casings at the crime scene, an exhaustive search of the area did not turn up the murder weapon. And Christie Downs, the only witness to the crime (her younger brother Danny was believed to have been asleep at the time), had suffered a stroke that impaired her speech and prevented her from telling police what she had seen.
Although Downs denied having ever owned a .22 caliber gun, two of her former lovers told police they recalled seeing her with one.
Meanwhile, Christie Downs was slowly beginning to tell what she remembered of the shootings. She said she had not seen a male stranger that night. A judge had already placed Downs' two surviving children in protective custody.
A break in the case finally came when investigators discovered Downs' secret diaries. They told of her obsession with a married man who didn't want her kids around.
"She saw the kids as a burden, they were in the way and he wasn't going to join her as long as she had the kids," Welch said. "And so the quickest, simplest way was to eliminate the children."
Police Arrest Diane Downs
Police arrested Downs Feb. 28, 1984, nine months after the shootings. In May of that year, the trial against Downs began with yet another inconceivable twist.
The woman who was on trial for shooting her own children was pregnant again -- and it was no accident.
In another one of her strange media appearances Downs spoke about the pregnancy.
"I got pregnant because I miss Christie and I miss Danny and I miss Cheryl so much," she said. "I'm never going to see Cheryl on Earth again and I just, you can't replace children, but you can replace the effect they give you. And they give me love, they give me satisfaction, they give me stability, they give me a reason to live and a reason to be happy, and that's gone, they took it from me, but children are so easy to conceive."
Downs had picked someone on her postal route to seduce prior to the start of her trial. Reporter Ann Jaeger remembers worrying that Downs' pregnancy could affect the way jurors viewed her.
"She calculated that this would win her sympathy in her trial. I mean, obviously, if she's pregnant, she loves children, right?" Jaeger said.
Star Witness at Downs Trial: Her Daughter
Prosecutors laid out the evidence against Downs, all leading up to their star witness. After months of physical and mental therapy, Christie Downs was finally able to take the stand and tell what happened to her that horrible night.
District Attorney Fred Hugi asked Christie if she remembered who shot her.
She replied simply: "My mom."
Downs was found guilty in June, and sentenced to life in prison plus 50 years.
Between the verdict and sentencing, the court recessed so that Downs could give birth to a girl she named Amy Elizabeth. The baby was taken by the state and delivered to adoptive parents. The girl was later renamed Becky Babcock.
In 1987, just three years into her sentence, Downs escaped from the correctional facility in Oregon where she was being held.
Within two weeks police had tracked her down to the home of another inmate's husband just blocks from the prison. After being recaptured, she was transferred to a more secure facility.
Diane Downs remains in prison in California. She was denied parole in December 2010 and will not be considered for parole again for ten years, when she will be 65. She continues to proclaim her innocence.
Watch the full story on "20/20" tomorrow at 10 p.m. ET.