Doctor's Mistress to Testify in Murder Trial The mistress of a Utah doctor accused of murder is scheduled to take a much-anticipated turn on the witness stand Friday. Prosecutors are trying to prove that Martin MacNeill plotted his wife's 2007 death while carrying on an affair with an aspiring nursing student, Gypsy Willis. The doctor invited her to the funeral, hired her as a nanny and asked her to marry him weeks later. Willis, 37, is on probation for identity fraud charges. Prosecutor Sam Pead called her a "begrudging" witness who will confirm she had the affair and insist it's over. The two were separated by MacNeill's jailing last year. MacNeill, 57, is accused of hounding his wife, Michele MacNeill, to have a face-lift, then mixing a lethal combination of drugs for her recovery and helping her into a bath tub. Defense attorneys counter that she died from a heart condition. MacNeill has said he found her slumped face-down into a tub of water. Early Friday morning, Fourth District Judge Derek Pullan ruled that MacNeill's youngest daughter will be allowed to offer limited courtroom testimony about how she found her mother's body submerged in a bathtub. Pullan said many of the girl's memories were tainted by an older sister who strongly believes Martin MacNeill killed his wife. Pullan says the now 12-year-old Ada MacNeill can be questioned only about an interview she gave a professional counselor several years ago. The girl was 6 years old when she found her mom in a tub in 2007. "Ada is highly susceptible to suggestion by Alexis (MacNeill) and has been influenced by adults in her life who are biased" and serve as her caretakers, Pullan said from the bench. The jury was not present for his ruling. On Thursday, two of MacNeill's oldest daughters testified that their father was eager to demonstrate how their mother ended up dead in the tub, and about how quickly he introduced a nanny who, according to the sisters, didn't cook, clean or take care of the youngest children. The oldest sibling, Rachel MacNeill, said while growing up, her father was her best friend and that she was closer to him than to her mother. When she learned of her mother's death, she didn't suspect her father and wanted to comfort him, she said. But her suspicions quickly grew at a family lunch after their mother's funeral that turned sour. Her father was "commenting on how he's a single man now, and he kept it very casual," Rachel MacNeill said. He was making jokes about being single, and he was laughing. It made me sick. I left.