After an autopsy shortly after her death, Utah assistant medical examiner Maureen Frikke who died in 2008 ruled the woman's death as natural, the result of cardiovascular disease matched with high blood pressure and an inflamed heart.
But investigators claim Martin MacNeill called Frikke multiple times and gave misleading information about how her body was found in their bath tub on April 11, 2007.
In 2010, in a new investigative report, Chief Medical Examiner Todd Grey changed the cause of 50-year-old Michele MacNeill's death to the combined effects of heart disease and drug toxicity. The manner of death was changed to "undetermined."
"I felt I did not have enough to justify the certification of homicide," Grey testified in Provo's 4th District Court on Thursday.
Grey said on Thursday that he believed drug toxicity did play a role in the woman's death, noting that four drugs were found in Michele MacNeill's body at the time of her death: oxycodone, promethazine, diazepam and zolpidem, which is also known as Ambien.
Grey said there was also some evidence that Michele MacNeill may have drowned, and pointed to reports from medical responders who said that while undergoing CPR, the woman coughed up several cups of water, some of it pink and frothy. But Grey said he could not be sure if that water came from the woman's lungs or stomach.
Though Grey said he did not see enough evidence in the woman's lungs to indicate that drowning played a role in the woman's death, he said it could still be possible.
"If you were to learn that the defendant told somebody that he had drugged up Michele MacNeill, and convinced her to get into the tub and held her down for a little bit, and it caused her death, would that scenario be consistent [with the autopsy results?]" Deputy Utah County Attorney Chad Grunander posed as a hypothetical question.
"Yes, it certainly is possible," Grey said.
Grunander also inquired whether Grey was "pressured" by Utah County Attorney's Office investigators to re-open the case and change the manner of death so their homicide investigation could continue. Grey denied this.
"You basically have no effect on my life," Grey told Grunander, adding that he does not work for the county attorney's office or law enforcement.
Michele MacNeill was found unconscious in a bathtub at their Pleasant Grove home by her 6-year-old daughter, Ada MacNeill. The child said during an interview at the Children's Justice Center in 2008 that she found her mother lying in the tub, fully clothed in pants and a blue jacket. The water in the tub was brown, the girl said.
Ada said her father sent her to the neighbor's house to get help.
Eventually, Michele MacNeill was pulled from the bathtub by a neighbor and Martin MacNeill. The two attempted CPR before medical crews arrived.
Those medical crews also attempted to perform CPR and other life-saving efforts before Michele MacNeill was taken to the hospital, where she was pronounced dead.
Martin MacNeill is on trial for allegedly killing his wife in order to continue an extra-marital affair with 37-year-old Gypsy Willis. He is charged with first-degree felony murder and second-degree felony obstruction of justice.
Also Thursday, defense attorney Randall Spencer spent about two hours Thursday morning drilling MacNeill's adult daughter, Alexis Somers, about her testimony the day prior, where she spoke about the days before and after her mother's death, including how she cared for Michele MacNeill in the days after she received a full face-lift. Spencer pointed to several inconsistencies between her testimony during the trial and her previous statements most of the inconsistencies being relatively minor, which Somers often dismissed by saying she "misspoke" or "miswrote" details.
Spencer also accused Somers of lying on her medical school application, listing her childless sister, Rachel MacNeill, as a job reference for a nanny. Somers said she listed her sister as a reference so she could speak about how she cared for her younger sisters.
Spencer also accused Somers of getting a physician friend to obtain her mother's medical records after she was denied access by the American Fork hospital where Michele MacNeill was treated on the day of her death because she was not the patient's spouse. But Somers said she asked her friend to check on her mother's condition because she didn't know yet that Michele MacNeill had died. She was, however, able to obtain her mother's lab results but not a full medical record through the friend.
Under redirect, prosecutor Chad Grunander asked Somers why she was seeking the information.
"Because I believe my father killed her," Somers said.
Somers also had testified that her mother was feeling fine the morning that she died. Spencer challenged this statement, playing an audio clip from Michele MacNeill's funeral, where she can be heard crying and saying, "The last time I spoke to my mom, she was feeling a little sick but "
Somers testified Thursday that she didn't remember her mother feeling sick that morning.
"There's a lot of things you don't remember in this case," Spencer shot back.
Testimony is expected to continue Friday, when two more medical experts will take the stand to testify about how they believe Michele MacNeill died. The trial, which began on Oct. 15, is scheduled to run for five weeks.