(CNN) -- — Martin MacNeill's fate is now in the hands of eight Utah residents who will decide whether the former doctor is guilty of killing his wife to continue an affair with a woman named Gypsy Willis.
During closing arguments Friday morning, prosecutor Chad Grunander pleaded with jurors to return a guilty verdict on both counts.
"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," Grunander said. "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, who has been on trial for 22 days in Provo, Utah, has pleaded not guilty to charges of murder and obstruction of justice. Prosecutors say he drugged then drowned his wife, Michele MacNeill, in the bathtub of their family's home on April 11, 2007, as she recovered from a facelift.
They also say Martin MacNeill's actions after his wife's death hindered the investigation, forming the basis for the obstruction of justice charge.
However, MacNeill's defense attorneys say that Michele MacNeill -- who was found with a powerful cocktail of prescription drugs in her system -- died of natural causes. None of the medical examiners who worked on the case could determine definitively whether she died as a result of homicide.
In his closing argument, defense attorney Randall Spencer said prosecutors had simply not proved their case.
"There's not evidence in this case that rises to level of guilt beyond a reasonable doubt," Spencer said. "The prosecution has presented to you their cherry-picked versions of the evidence that is most consistent with their theories."
Daughters took the stand
Rachel MacNeill, the MacNeills' oldest biological daughter, was in attendance at Friday's proceedings and began to cry as the judge read jury instructions before closing arguments even began.
The MacNeills had eight children and -- to many in their community -- seemed to be living an idyllic life in a gated community when Michele MacNeill died. More than one of the children, however, have since come forward and accused their father of killing their mother.
Judge Derek Pullan handed the case to the jury Friday afternoon after hearing from 50 witnesses over 13 days of testimony.
Several of the MacNeills' daughters were among the 46 witnesses who took the stand for the prosecution. They testified about the former doctor's allegedly suspicious behavior leading up to and following their mother's death.
One daughter, Alexis Somers, testified that her mother seemed overmedicated after having facelift surgery -- so much so that Somers had difficulty waking her up.
"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,'" said Somers. "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.'"
Prosecutors also called Willis, Martin MacNeill's former mistress, to the witness stand. She admitted to having an affair with Martin MacNeill both before and after Michele MacNeill's death.
Less than two weeks after his wife died, MacNeill hired Willis as the family nanny to take care of his four youngest children.
"I would get up, make sure they were getting ready for school, getting breakfast. 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," said Willis.
Willis never married Martin MacNeill, but she said she still came to call herself "Jillian MacNeill," and engaged in falsifying documents under that name.
Prosecutors entered into evidence an application for an identification card that would have allowed Willis -- as "Jillian MacNeill" -- to have access to military bases. On the form, the couple's wedding date is listed as April 14, 2007, the day of Michele MacNeill's funeral. Willis testified that Martin MacNeill filled out the form.
MacNeill and Willis were eventually prosecuted for identify theft. MacNeill pleaded guilty and was sentenced to four years in federal prison, while Willis served two years.
Several men who served time behind bars with MacNeill also testified for the prosecution and discussed what they say MacNeill told them about his wife's death.
"He just pretty much opened up about it," a man identified as inmate No. 1 said Wednesday, the 12th day of the trial. "He said he had gave her some oxy and some sleeping pills and then got her to get in the bathtub. 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."
A brief defense
Defense attorneys wrapped their case after calling four witnesses to the stand Thursday, two of which seemed to support MacNeill's alibi that he couldn't have killed his wife because he was at his place of employment -- the Utah State Developmental Center -- when she died.
The defense also called Brett Besser, an ergonomics expert, to testify about why he believes MacNeill had trouble removing his wife's lifeless, 180-pound body from the bathtub where she died. Prosecutors have suggested that MacNeill was dishonest in describing his alleged inability to remove his wife's body from the bathtub before rescuers arrived.
The prosecution has alleged that Martin was dishonest about how he struggled to get her lifeless body out of the bathtub, delaying rescue efforts.
Besser said his calculations indicate that only 7% of the male population MacNeill's age and size could have lifted his wife safely out of the tub. Prosecutor Sam Pead suggested, however, that Besser's expertise provides better analysis in the context of workplace safety issues -- not protocol in emergency situations.
If convicted of first-degree murder, MacNeill could be sentenced to anywhere from 15 years to life in prison. If convicted of obstruction of justice, he faces 15 years behind bars.