Transcript for Justice for Michele MacNeill
"20/20's" "The perfect nanny" continues. Once more, Elizabeth vargas. Taking center stage. Reporter: It was called "The murder in the bathtub" case, gripping the country for weeks. She finds her mom dead in the tub. Martin Macneill on trial for the death of his wife. Reporter: Martin Macneill sat in a Utah courtroom charged with the pre-meditated murder of his wife and mother of their eight children. His chief accusers, his own grown daughters, who believe their dad was a killer. But martin's defense team that stuck Michelle's death was from natural causes. Martin Macneill is innocent, ladies and gentlemen. Reporter: The trial begins with Michele's plastic surgeon, Dr. Scott Thompson. He recalls the laundry list of drugs he prescribed for Michele following her six-hour facelift surgery. Cephalexin, the cephalexin is the antibiotic. The ambien for the sleeping the azithromycin eye ointment and then the medrol dose pack for the swelling. Reporter: Thompson admits that he wouldn't normally prescribe so many drugs, but that martin, a fellow physician, assured him he wouldn't let Michele take too many pills. Why did you prescribe it here? Because martin was a physician and he asked me for these things. Was it your intention that Michele take all these drugs together? No. Would you have prescribed this combination to her if martin was not a physician? No. Reporter: On the stand, martin's daughter Alexis testified that martin forced Michele to take more drugs than she wanted. She said, "Lexi, I don't know why, but your dad kept giving me things and telling me to swallow." She said, "I even started to throw up and then he kept giving me medication." Did she have requests? She made me take out every skinle pill from the pill bottle and she wanted to know what the pill felt like in her fingers. So she knew what my dad was giving her. Because at that time she couldn't see. Reporter: But the jury won't hear a crucial piece of evidence, something that Alexis revealed to "20/20" about Michele's fears justs before her death. She says, "If anything happens to me, make sure it wasn't your dad." Reporter: Those words are ruled too prejudicial by the judge, and the jury never hears them. So the prosecution instead hones in on martin's movements the morning Michele died. There's about an hour and a half period of time where no one really knows where martin is. Reporter: A timeline showed a 90-minute gap between the time martin left work and when he picked up 6-year-old Ada from school. Plenty of time. Rush home, take care of your business, give Michele the drugs, fix her up a bath, get her in the tub, hold her head down for a little while and help her out. Reporter: Witnesses say martin was frantic that day. I could hear martin yelling that he needed help. I asked him what happened. What did he tell you? He said, he went into the room and he described it as he saw her faced down the wrong way in the tub. Reporter: As a crucial center piece of their case, prosecutors haul in a replica of the bathtub where Michele was found. This bathtub, ladies and gentlemen has an important story to tell. Okay? Reporter: Witnesses re-enact what they saw. Neighbor Kristi Daniels testifies that she found Michele facing up and lying inside the bathtub and partially dressed, that contradicts the scene. Was Michelle dressed or not? What I remember is Michelle had a long black-sleeved shirt and nothing else. Okay, no bottoms? No bottoms. Reporter: Prosecutors contend that martin attempted to make it to look as though Michele had been taking a bath and slipped under the water. But he had been interrupted when the neighbors arrived much sooner than he had expected. It's a very small bathtub. It'd be almost impossible in this bath to slip under the water. Reporter: So, why would martin try to stage a drowning accident? Prosecutors argues it all comes back to gypsy. He was at a crossroads. He had to choose between Michele and gypsy. He chose gypsy. He chose gypsy over Michele. Reporter: And although it's martin on trial for murder, it seems as though everyone has something to say about gypsy. It's gypsy Jillian Willis. Her name is -- Gypsy Jillian Willis. Gypsy Jillian Willis. The jury hears how martin lied to his younger children, telling them gypsy was just the nanny. Because she was nothing like my mom. Did you ever see your dad and Jillian interact? Yes. What did you see? I remember her going up to my dad's room at night, and have the door closed, and I remember staying up at night and thinking, what in the world is -- why is she up in dad's room? She's the nanny. Reporter: The testimony of his children may have been devastating to martin Macneill, but what may have sealed his fate was his former cellmates, while serving in prison sense for identity fraud. Did martin talk about the relationship he had with his wife before she died? A little, yes. That she was not going to let him keep cheating on her. Did he say he was cheating on her? Yeah, he told me about his girlfriend. I don't remember. I don't recall. I don't recall the name. Her name was gypsy or dipsy or something. Doc, they said you murder your wife. I can get a way with a lot of things. Did he say anything else? Got away with murder of his wife. I just went up to him and said, I apologize about your wife. He said, I'm glad the Is dead. . Reporter: There's no proof that Michele is a murder victim. They continue to cling to the original autopsy report, citing a natural death. They don't raise to the level of proof beyond a reasonable doubt. Reporter: The jury doesn't buy it. Has a jury reached a verdict? Reporter: The jury returns a verdict. Martin is stone-faced. Guilty of first degree murder. It was such a relief. I've been fighting for this so long, and I never thought we'd come to this day. I never thought that it would even come to trial, and then to be in that courtroom and hear, "Guilty," it was just a flood of emotions. Reporter: Her father will likely be in prison for the rest of his life. And if woman at the center of the story, she has an alibi and she was never charged with anything related to her death. But Alexis is not convced. I do believe that gypsy was involved with my mother's death. She was the motive and I know she knows more than she portrayed in court. Reporter: So many people think you must have known or in on it? That's incorrect. Reporter: They choose not to dwell on that question. Finally having justice for my mother who means everything to me and she was taken away from me from all of us, we're finally getting justice for her. Tonight, martin Macneill is still behind bars, waiting to be sentenced, he faces 15 years to life. As for gypsy, she's now hired a publicist, she plays]
This transcript has been automatically generated and may not be 100% accurate.