One daughter's mission to prove her mom did not commit suicide. Michigan police believed that but michelle romaine is sure her mom was murdered. She says she has evidence to prove it. Reporter: Good... See More
One daughter's mission to prove her mom did not commit suicide. Michigan police believed that but michelle romaine is sure her mom was murdered. She says she has evidence to prove it. Reporter: Good morning, george. She says there are witnesses with key information that went ignored. Sightings of a speeding car and suspicious men near the area where her mother was last seen. This crusade, four years later. To convince investigators her mother did not kill herself. This morning, michelle and michael romaine are fighting to get their mother's case reopened. Four years ago, joanne disappeared after leaving a church in michigan. Her bodice covered more than two months later floating in the detroit river. Police ruled the death a suicide, claiming the 55-year-old drowned her. Michelle says her mother was concerned someone was following her. There are many clues that show foul play involved. Reporter: Michelle hired a private investigator. In short, I think this was a murder. Reporter: The investigator found new evidence, among those, her mother's shoes. Other than clay from the river, they were in impeccable condition, consistent with her being carried, not the police theory that she walked over metal rods before walking into the river. She slams her mother's purse had rips in it that weren't there the morning before her mother disappeared. AN AUTOPSY SHOWED PRUZs ON HER Upper left arm, the arm where she carried her purse. Her car was found if a different parking spot from where she originally parked. Local police say they're insi insisting it's a suicide, but will reopen the case with enough real evidence. It would take substantial evidence, like the identity of a killer. That's myself, michelle here. Reporter: Still, michael and michelle won't stop fighting. We will not rest until the killers are found. Reporter: The most important piece of evidence they say is their mom just wasn't the type of person to commit suicide. They also say that she gassed up her car the same day she disappeared. They wonder why a woman who intended to take her own life would bother to do that. Now more of last night's golden globe awards.
This transcript has been automatically generated and may not be 100% accurate.