Utah doctor Martin MacNeill (R) was convicted of first-degree murder for the death of his wife, in a trial that captured national attention. REUTERS

A Utah jury has found Dr. Martin MacNeill guilty of first-degree murder and obstruction of justice for killing his wife in order to pursue a relationship with his mistress.

According to HLN, MacNeill, 57, is facing 15 years to life in prison for murder, and up to 15 years for obstruction of justice. He is scheduled to be sentenced on Jan. 7.

Prosecutors argued that MacNeill convinced his wife, Michele MacNeill, 50, to have plastic surgery in order to drug her during her recovery and drown her, so that he could continue his relationship with his alleged mistress, Gypsy Willis, ABC News said. Michele MacNeill died on April 11, 2007.

"Martin MacNeill murdered his wife Michele. Her death was not the result of an accident, and it certainly was not the result of a heart condition," prosecutor Chad Grunander said during closing arguments on Friday. "The defendant carried out a cold and calculated plan to murder his wife. He relied on his knowledge and experience as a doctor and also as a lawyer to accomplish this."

MacNeill’s defense team argued that Michele MacNeill, who was found with a cocktail of prescription drugs in her system, died of natural causes. As HLN points out, no medical examiner who worked on the case could say with absolute certainty whether her death was a homicide.

"There's not evidence in this case that rises to level of guilt beyond a reasonable doubt," defense attorney Randall Spencer said. "The prosecution has presented to you their cherry-picked versions of the evidence that is most consistent with their theories."

According to CBS, the defense claimed that Michelle MacNeill had a heart attack and fell head first into the tub. An autopsy showed she had an enlarged heart, an artery narrowing in the heart and a deteriorating kidney and liver.

The case captured national attention for its mixture of sex, drugs and murder in the seemingly idyllic community of Pleasant Grove, just south of Salt Lake City . As CBS points out, Martin MacNeill was the medical director of the Utah State Developmental Center, a residential facility for people with “intellectual disabilities,” according to the official website. He also held a law degree and was a former bishop in a Mormon congregation.

According to HLN, Martin MacNeill and his wife had eight children, several of whom testified against him during the trial.

"I went to my father and I said, 'What happened? Obviously, Mom is overmedicated.' He said, 'Yeah, I think I gave her too much medicine. I must have given her too much medicine,'" one daughter, Alexis Somers, told the jury. "I asked her what happened ... She said, 'Lexi, I don't know why, but your dad kept giving me medication. He kept giving me things, telling me to swallow.'"

As HLN notes, Martin MacNeill hired his mistress, Gypsy Willis, as the family nanny to care for his four youngest daughters, less than two weeks after Michelle MacNeill died.

"I would get up, make sure they were getting ready for school, getting breakfast,” she said. “I'd take them to school. I'd go to my nursing classes. I would come back. I'd take them to dance, we'd stop at the grocery. I'd help make dinner if Martin wasn't cooking.”

Both Gypsy Willis and Martin MacNeill were also convicted of identity theft after Willis began using the name “Jillian MacNeill” in official documents. In one form, she listed her wedding date with MacNeill as April 14, 2007, the day of Michelle MacNeil's funeral, HLN said.