Investigators faced a perplexing question: Did Ashley write the suicide note and kill her two fathers? Or could it be possible that Stacey had killed her two husbands and now tried to murder her own daughter in attempt to frame her?
Lead detective Spinelli believed Stacey Castor was responsible. "Stacey knew our grip was getting a lot tighter on her. There was really no way out of it besides using her daughter as a scapegoat."
Stacey was arrested at the hospital and charged with the murder of her second husband and the attempted murder of her daughter.
"I would die for my kids," Stacey said. "I could never hurt them like that. Ever. My kids were my life. I could never do that to Ashley."
Prosecutors believed Stacey Castor was guilty, but she maintained her innocence.
"How can you sit there and blame your own child?" Ashley asked. "That's what I just don't get. I didn't try to kill anybody, and I would never kill anybody."
But Ashley's grandmother, Judie Eaton, believes in daughter Stacey Castor's innocence.
"I have woke up in the middle of the night, and you just lay there and you think, How did this happen?" she said. "She doesn't deserve this."
Eaton also indicates that Ashley had "ample time and opportunity" to have committed the murders.
Soon mother and daughter faced off in court, and "20/20" was granted full access to all sides of this curious investigation and trial.
Stacey Castor talked about the trial and her conviction in an exclusive interview with ABC News' David Muir, who also sat down with the lawyers, detectives, doctors, family and friends who spent a decade watching this mystery unravel.
Go to the "20/20" page at ABCNews.com all week for more on this story and watch the two-hour special Friday on "20/20" at 9 p.m. ET.