Once law enforcement is involved, Garrett said, the next step is to stage a false murder. In Dippolito's case, she returned home one day only to be greeted by a policeman who said her husband was murdered inside their house. It was a setup for police to see how she would react.
Even in the interrogation room after she was brought in for questioning, Dippolito continued to speak as the shocked widow. Garrett explained that even though the police were in on the fake murder, they were trying to see if Dippolito would crack and tell the truth.
"A case is always much better if you can get people to actually admit that they have committed this act," he said.
Dippolito allegedly told her fake hit man she would pay $3,000, plus the cost of a gun, to get rid of her husband.
In the case of Matthew Campbell, he allegedly negotiated to pay his hired assassin $5,000 up front, and then $5,000 after he murdered Campbell's mother.
Campbell's mother told ABC News she is still in shock, and doesn't understand why her son would plot to kill her.
Matthew's sister Nikki, who also may have been targeted by her brother, said she never saw this coming and didn't think Matthew would do it for money.
"He knows that even if my mom was gone, he knows that two of us are still here so he's not going to get full financial gain out of what my mom owns," she said. "The whole idea that your brother would kill you it just sounds so completely off the reservation."
In his apology letter to his mother, Campbell apparently explained that he did it because he was in way over his head and the whole thing was a big misunderstanding.
"I was so scared mom. I didn't know what else to do. I thought I was really dealing with a real hit man that wouldn't hesitate to do anything, like in the movies. So I made a phony plan to this just to get him away from me," his mother read from her son's letter.
Dana isn't buying her son's excuse though. "I do love him. I do. He's my son and no matter what I will always love him," she said. "[But] no, I don't trust him at all."
ABC News' Lauren Effron contributed to this report.