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 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.
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.