On May 19, 1983, prosecutors contend that Downs shot her three children, Stephen Daniel (born 1979); Cheryl Lynn (born 1976); and Christie Ann (born 1974). Downs drove the children in a blood-spattered car to McKenzie-Willamette Hospital. There was blood spatter all over the inside of the car but none on Diane. On arrival at the hospital, Cheryl was already dead. Danny was paralyzed from the waist down and Christie suffered a disabling stroke. Downs herself had been shot in the left forearm. Downs claimed she was carjacked on a rural road near Springfield, Oregon, by a strange man who shot her and her three children.
Investigators and hospital workers became suspicious because they decided her manner was too calm for a person who had experienced such a traumatic event. She also made a number of statements that both police and hospital workers considered highly inappropriate.
Their suspicions heightened when Downs had, upon arrival at the hospital to visit her children, called Robert Knickerbocker, a married man and former co-worker in Arizona, with whom she had been having an extramarital affair.[9] The forensic evidence did not match Downs' story; there was no blood on the driver's side of the car, nor was there any gunpowder residue on the driver's door or on the interior door panel. Knickerbocker also reported to police that Downs had stalked him and seemed willing to kill his wife if it meant that she could have him to herself; Knickerbocker stated that he was relieved that Downs had left for Oregon and that he was able to reconcile with his wife.[10] Downs did not tell police she owned a .22 caliber handgun, but both Steve Downs (her ex-husband) and Knickerbocker (her ex-lover) said she did own one.
Investigators later discovered she bought the handgun in Arizona; and, although they were unable to find the actual weapon, they found unfired casings in her home with extractor markings from the same gun that shot her children. Most damaging, witnesses saw Downs' car being driven very slowly toward the hospital at an estimated speed of five to seven mph, contradicting Downs' claim that she drove to the hospital at a high speed after the shooting. Based on this and additional evidence, Downs was arrested on February 28, 1984, nine months after the event, and charged with one count of murder and two counts each of attempted murder and criminal assault.[11]
Prosecution
Prosecutors argued that Downs shot her children to be free of them so she could continue her affair with Knickerbocker, whom (she claimed) let it be known that he did not want children in his life. Much of the case against Downs rested on the testimony of her surviving daughter Christie, who, once she recovered her ability to speak, described how her mother shot all three children while parked at the side of the road and then shot herself in the arm. Christie was eight years old at the time of the murder and nine years old at the time of the trial.