Utah doctor goes to trial for murdering wife: Part 2

After being convicted of fraud for giving his adopted daughter's identity to his mistress, Gypsy Willis, Martin MacNeill was convicted of murder and sentenced to 15 years to life in prison.
5:32 | 06/15/19

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Transcript for Utah doctor goes to trial for murdering wife: Part 2
Investigators have Dr. Martin Mcneill and his lover where they want them, behind bars. The last sentencing hearing, the only thing he said to me is I hope you're happy, Alexis. Reporter: All of Michelle Mcneill's daughters believe martin Mcneill killed her, what do you think. We believe there's probable cause to think there's foul play here. Michelle's sister pushed and pushed and pushed until authorities agreed to review Michelle Mcneill's toxicology report, and when they did, they found a toxic drug cocktail. Finally success. It was changed from natural to undetermined. Long story short, undetermined opens the door to the possibility of murder. Martin Mcneill was charged with murder of his wife Michelle. After long years of fighting for justice for Michelle, there was such tension around finally going to trial the defense's position was that Michelle died accidently. The prosecution presented a case that martin had meticulously plotted Michelle's death. Dr. Scott Thompson was the plastic surgeon who performed the face-lift. Hydrocodone, two pain medication prescriptions. Why did you prescribe it Because martin was a physician and asked me to prescribe these things. Was it your inessential that she take these things together? No. This bathtub has an important story to tell. There's about an hour and a half period of time where nobody knows where martin is. Rush home, give Michelle the drugs? Fix her up a bath, get her in the tub, hold her head down? Martin described finding Michelle in the tub as if she was outside the tub but bent over with her head under the water when in reality she was found entirely inside the tub with her head up above the water. Reporter: Inmates learned he was suspected of killing his wife after watching a television show. He just pretty much opened up he said he had gave her some oxy and sleeping pills and got her to get in the bathtub. Did he say what he did next? Later on he just said he had to help her out, and I asked him what that was, and he said he held her head under the water for a little while. The jury was left trying to determine who was telling the truth. Dr. Martin Mcneill? Or an inmate in the texarkana federal pen. It was about 1:15 in the morning when the jury came in and delivered their verdict. Mr. Mcneill, if you will stand please. We the jury fine the defendant as to count one, murder, guilty. I burst into tears. As to count two, obstruction of justice, guilty. It took my breath away. Gypsy Willis was never charged with murder because we couldn't prove she was involved, as either a direct participant in Michelle's murder or an accessory. We believe she was the motive, but we didn't have the evidence to prove that she murdered Michelle or was an accessory to her death. So many people think you must have known. No. Or that you were in on it. That is incorrect. I don't believe martin murdered Michelle. Reporter: What would you say to Alexis and Rachel? I am so sorry for any role I played in anyone's pain. I don't think she has any remorse. She's an evil person. Reporter: In 2017, martin Mcneill delivered one more shock to the family. A Utah doctor who murdered his wife was found dead today at the Utah prison. It appears to be a suicide. Alexis called me and we both screamed and cried. He had recently lost liis his appeal and was going to remain in prison. Rachel and I were standing over his body, seeing him in the funeral home. I was able to tell my father that I forgive him, that I loved him and not feel fear. And not feel anger. I was able to let go of the feeling that hatred and pain and just obsessing over my father's act. Alexis ended up successfully adopting her little sisters and has raised them with Ada, Sabrina and elle. Reporter: Alexis is now married with children of her own. It's going to melt! I can't imagine how much joy she'd have with my children, being in our lives. She's missed out on so much. We celebrate her every January 15th, balloons and cake, and she would have been 62. Blow them out, Sophie.

This transcript has been automatically generated and may not be 100% accurate.

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