Utah doctor's mistress set to testify in murder trial

The mistress of a former Utah doctor accused of murder is scheduled to take a turn on the witness stand Friday.

Prosecutors are trying to prove that Martin MacNeill plotted his wife's 2007 death to carry on an affair with the woman, Gypsy Willis. Her appearance in the household as a nanny raised suspicions early on for the doctor's oldest daughters.

Willis is on probation for identity fraud charges.

The 57-year-old MacNeill 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.