Hilary Swank (left) with Betty Anne Waters in New York on Tuesday. (AP)

Bristol, Rhode Island, Oct. 13: Betty Anne Waters still greets her lunch customers here as they tuck into pints of Guinness and Reuben sandwiches at Aidan’s, a pub hard by the harbour in this small, boat-building town.

Waters had only a job as a waitress, her high school equivalency, two kids and a stack of bills when she set out to rescue her brother Kenneth Waters, who served 18 years in prison for a murder he did not commit. Now she has a college degree, a law degree and the stunning achievement of having succeeded, after nearly two decades, in overturning her brother’s conviction.

But after he was released in 2001 — and the flurry of news attention faded — Waters, 56, returned to Aidan’s, to the simple life of tending to her family and the pub where she is now general manager. No law firm. No fat salary. No fame.

“As I got to know her, I understood it,” said Barry Scheck, a lawyer who assisted her on the case. “She did not become a lawyer to be a lawyer. She became a lawyer to get her brother out of jail.”

Come Friday, though, when the movie Conviction opens in select cities, considerably more people will get to know Betty Anne Waters. The movie, starring Hilary Swank as Waters, tells her story; how she doggedly searched for DNA evidence that had supposedly been destroyed; how she enlisted Scheck and his Innocence Project to join in her quest; and how she, Scheck (played by Peter Gallagher in the film) and her friend Abra Rice (played by Minnie Driver) went house to house, getting witnesses to admit they had lied under police pressure.

“I’m not going to say this is fun for me; I’ve had fun moments,” she said. “I’m tired right now. I could never keep this up.”

Aidan Graham, who has employed Waters at his pub as a waitress, bartender or manager for much of the past two decades, said: “She’s a very private person; she doesn’t like the limelight.”

Sitting in a booth at Aidan’s on a recent sunny afternoon with the water glistening behind her, though, Waters was positively voluble when it came to discussing Conviction, directed by Tony Goldwyn (“They really cared about getting it right”), and her work in helping those who have been wrongfully convicted. She now volunteers for the Innocence Project, which Scheck co-directs and which works to exonerate the wrongfully accused. She speaks out against the death penalty, lobbies for legislation on criminal-justice reform and evidence preservation, and meets with prisoners who have been freed.

“It makes me happy that I can help people who’ve helped me,” she said.

Her brother pushed her towards law. Charged with the murder and robbery of a next-door neighbour, Waters was convicted in 1983 and incarcerated after a failed appeal in 1985. He had attempted suicide and spent a month in isolation. Waters needed him to promise that he would not try to hurt himself again. He agreed, as long as she got the education that would help free him.

“I remember saying to my sister: ‘Am I going to make it through school, pass the bar? What if I don’t find the answer?’ ” she recalled. “It seemed like as long as I was doing something in school, Kenny was okay.”

“I don’t think Betty Anne feels like she put herself on hold,” Swank said in a telephone interview. “I think she feels: ‘That’s my life. That’s what I was here to do, was to help and be of service to people who are innocent’.”

In a television interview at the Los Angeles premiere,. Goldwyn said: “I’ve been working on this for nine years, which is a little less than half the time Betty Anne Waters spent fighting to get her brother out of prison. So any time I started feeling bad about the ups and downs of getting a movie made, I just thought about Betty Anne’s determination and my obligation to her to get this done.”

The film captures the childhood closeness between Waters and her brother, played by Sam Rockwell.“He always made me feel like I could be anything, do anything,” she said.

Six months after Kenneth was freed, he fell off a wall while taking a shortcut home through the dark, hit his head and died. To people close to Waters, it was the cruellest kind of fate. Test audiences couldn’t take such a tragic ending, the filmmakers said, so the movie leaves it out. But Waters speaks of the loss without self-pity or bitterness.

“Kenny had the best six months of his life,” she said. After so many years behind bars, the world was new to him, she added. He was amazed by cellphones, confounded by the many unfamiliar gadgets blinking on the car dashboard.

Many are surprised at how little transformed she is by her experience, how normal it seems to see her at Aidan’s these days, or at home cooking meatballs and apple pie for her large extended family.

“I just want to be a grandmother,” she said last week, after chatting with the fiddlers who play at Aidan’s during the lunch rush.