LEWISTON – Tonia Ross believes someone knows who killed her mother, Dorothy Milliken.

Though it will be 30 years Monday since someone found Milliken’s bludgeoned body outside a Lisbon Street laundromat, police have never made an arrest.

The case has remained open, but cold.

Her family hopes money can heat it up again.

On Monday, they plan to hold a news conference at the corner of Lisbon Street and Dumont Avenue, where Milliken was found, to offer a $5,000 reward in the case. The money would be contingent upon the arrest and conviction of the killer.

“I know for a fact that there is someone out there who knows what happened,” said Ross, who was 7 when her mother was killed on Nov. 6, 1976.

Milliken, a 26-year-old mother of three, was killed in the early morning hours beside Beal’s Laundromat. Shortly after arriving to do laundry at about 2 a.m., she was struck over the head with a heavy object. Her body was found hours later, but no weapon surfaced. The investigation did not result in an arrest.

Over the years, Ross, now 37 and living in Sabattus, has done her own investigating. Finding an answer to her mother’s death has become an obsession at times.

“It’s at the front of my mind every day,” she said.

She checks in with police three or four times a year and shares any information she learns.

“I try not to get too worked up about it,” she said. “It’s not anger. It’s frustration that the case hasn’t been solved.”

Her entire family has been asking fundamental questions for three decades.

“There are no answers,” she said. “We want to know who, and I want to know why.”

Such questions always lead to her belief, her intuition, that someone knows the answers.

“I hope they are happy and they sleep well at night,” she said acidly.

Although police don’t speak directly about evidence or suspects, it has been well-reported in the past that more than two dozen possible witnesses have been interviewed about Milliken’s slaying.

If someone has been hiding the knowledge for all these years, maybe the money will bring someone forward.

“I wish it were more,” Ross said of the reward, which is being offered from her family.

Ross has had to tell her own girls, ages 12 and 17, about the death that changed her life.

“I tell them, ‘My mother was taken away from me at a very young age,'” she said. “Family is the most important thing.”