But that wasn't all. Witney discovered MacNeill served in the U.S. Army for less than two years in the mid-1970's, and was discharged for a psychiatric disorder. Witney discovered that over the next three decades, MacNeill was able to collect more than $100,000 in disability payments from the Veteran's Administration. By the time Utah investigators uncovered it, the amount was up to up to $3,000 a month. The VA confirmed to ABC News that MacNeill collected benefits, but the agency would not comment further.
And there was more. As Doug Witney peeled back the layers, he discovered MacNeill was put on felony probation for three years in 1977 for writing phony checks in California. According to Gary Ryan, a former assistant district attorney in Orange County, MacNeill had used the checks to pay for, among other things, home furnishings, jewelry, 60 pairs of socks, two dozen pairs of shoes and a year's supply of chocolate-covered cherries.
A store employee suspected MacNeill was using phony checks and alerted police.
"I remember him because he was bright and he was a con, and cons always interested me," said Ryan, who prosecuted MacNeill. "They were people who if they had pursued legitimate things in their lives should have been a success. And he should have been a success. He had all the talent in the world."
It was a talent he turned into a career posing as a doctor for three decades, said Witney.
"Here is a man who went to jail for 180 days; was put on felony probation -- or parole -- for three years; was on felony parole when he went into medical school," he said.
MacNeill's daughters, Rachel and Alexis, were shocked to discover the father they adored had a criminal background and fraudulent credentials.
"The father we knew … he was just a façade," said Alexis.
"He was able to hide an entire life from us," said Rachel. "We basically found out that our entire lives had been based and surrounded on lies. That everything about our experience with our father was a lie."
Next, investigator Doug Witney and Jeff Robinson, Chief of the Bureau of Investigations for the Utah County Attorney's office, took a closer look at MacNeill and his relationship with the woman now living in the house as the "nanny," Gypsy Willis.
Witney said MacNeill and Willis apparently met in a chat room on the Internet. Investigators believe MacNeill communicated with many women over the years, but that his relationship with Willis started to take on a life of its own.
"I truly believe that she believed that she could control men by an aura about her," said Witney. "He eventually put her into an apartment that he paid for … and then their relationship became very heated."
After Michele MacNeill's death, Willis eventually took MacNeill to Wyoming to meet her parents -- Harold and Vicky Willis.
"He said, 'I never loved Michelle, but I love Gypsy,'" said Vicky Willis. "And I said, 'but you had a family with Michelle'… He says, 'Actually, I loved her as a friend, I loved her as a sister, but I never loved her like I love Gypsy.'"
Martin even proposed to Willis in front of her family, at a restaurant in Wyoming. Willis' sister, Julie, was there.
"He gives this grand speech about how he loved her, and how he loved her from the moment he saw her," said Julie Willis. "And he knelt and proposed to her, and Gypsy cried. It was very fairy tale."