"He kept repeating that we need to have an autopsy done," Rachel, 34, tearily testified in a Provo, Utah, courtroom Thursday, "because he didn't want anyone to think that he murdered my mother. I asked him 'Why would anyone think that?' It was so shocking."
Martin MacNeill, a once-respected medical doctor and lawyer, is on trial for the first-degree murder of his wife of almost 30 years, Michele. Utah County prosecutors allege MacNeill pressured her into having plastic surgery, overmedicated and drowned her in the family bathtub so he could start a new life with his mistress.
MacNeill, 57, who could get life in prison, has pleaded not guilty, claiming his wife died from natural causes due to heart disease.
Bizarre BehaviorRachel, at times trembling on the stand, described how her father, a former Mormon Sunday school teacher, was once "her best friend" and that they were a "close family."
On the day her mom died, Rachel says she discovered her mother's wet, blood-stained running suit and undergarments hastily piled in the garage. When she showed them to her father, she testified, he reacted with rage: "How dare you show me those things. Get rid of them," he allegedly said.
Rachel added that at a luncheon following her mother's funeral, her father was "making jokes about being single and laughing," she said. "It made me sick."
Introduces MistressJust days following their mother's funeral, Rachel added that her father introduced a woman, Gypsy Willis, now 37, as a new nanny to the family's younger children, which struck Rachel as odd.
"I expected her ... to cook, clean, or take care of the children," Rachel testified, who recoiled with disgust when prosecutors showed her a photo of Willis. "[But] she was sitting there staring at my dad, she was [making] goo eyes at my dad."
Rachel testified that, to her horror, it was immediately apparent that her father and Willis were romantically linked. (Willis admitted in a pre-trial hearing to having been in a sexual relationship with MacNeill while he was married after the pair met online in 2005.)
In cross examination, MacNeill's defense attorney, Susanne Gustin, got Rachel to concede that her father at times cried and appeared distraught after losing his wife. Gustin also attempted to cast doubt on Rachel's testimony by questioning Rachel about her past bipolar disorder diagnosis.
Past FraudMacNeill and Willis were both convicted of identity theft in 2009, after MacNeill abandoned one of his adopted daughters in her native Ukraine so Willis could assume her identity to mask her bad credit.
Authorities also say that MacNeill's entire career as a doctor was based on fraud, since he allegedly falsified school transcripts and admissions forms. "The fact that he was practicing medicine this whole time is disturbing," Utah County Attorney's Office chief investigator Jeff Robinson previously told PEOPLE.
It was only after Rachel, her sister Alexis, 30, and their aunt, Linda Cluff, 53, waged a five-year-long campaign, that MacNeill was charged with murder in 2012.
Testimony resumes in the trial Friday, with MacNeill's mistress expected to testify.