Betty Tyson, who spent half her life in prison for the brutal murder of a businessman in a gloomy alleyway in Rochester, N.Y., before a judge ruled that she had been wrongfully convicted, died on Thursday in Rochester. She was 75.

Her sister, Delorise Thomas, said the death, in a hospital, was caused by a heart attack.

On May 28, 1998, 25 years to the day after she was arrested, Ms. Tyson, 49, left the maximum-security Bedford Hills Correctional Facility in Westchester County and headed home to freedom after Monroe County’s district attorney announced that he would not seek to try her again. By then she had become New York State’s longest-serving female inmate.

The judge’s ruling and the prosecutor’s decision effectively ended the investigation into a murder that had prompted allegations of police brutality and coerced testimony, as well as concerns about how the case could have been pursued to a conviction despite so many reasonable doubts.

“Betty’s was one of the early wrongful-conviction cases, and in many ways it alerted people to the possibility that these things could happen,” Gary Craig of The Rochester Democrat and Chronicle, whose reporting reopened the investigation and helped provide Ms. Tyson’s lawyer, Jon Getz, with the legal ammunition to set her free, said in a phone interview.

The outcome also left the murder unsolved — although the district attorney, Howard Relin, said at the time that he still believed that Ms. Tyson was guilty. He decided, he said, that since she had already served the minimum of her sentence of 25 years to life and many of the witnesses were dead, the chances of another conviction were slim.

“Nothing would be gained for this community by trying Betty Tyson again,” he said. “But this is not a determination that Ms. Tyson is innocent.”

Ms. Tyson was 24 and working as a prostitute to support what she described as a $300-a-day heroin habit in 1973 when she and John Duval, a cross-dresser who had previously been arrested on prostitution charges, were arrested in the murder of 52-year-old Timothy Haworth, a photography consultant to the Eastman Kodak Company. The police said Mr. Haworth was apparently seeking to hire a prostitute when he left his hotel after work. He was found bludgeoned with a brick and strangled with his own necktie.

Ms. Tyson, who was Black, said she was beaten by the police for 12 hours while still strung out on drugs when she confessed to the murder. She later recanted. The only physical clue, tire tracks found near the murder scene, did not match the treads on her car. But two male teenagers who had been held for seven months as material witnesses ultimately said that they had seen her with the victim. An all-white, all-male jury voted to convict. (Mr. Duval was also convicted and served nearly 26 years in prison before his conviction was also overturned.)

Mr. Craig, the Democrat and Chronicle reporter, began to reinvestigate the case after being prodded by Robert Tischler, a friend of Ms. Tyson’s family. He found that Detective William Mahoney, who extracted the confession, had resigned in 1980 after fabricating evidence in another case.

Mr. Craig won the confidence of one of the two material witnesses, who retracted his account in 1997. His reportage prompted the prosecutor’s office to comb the original police files and review an initial statement from the other supposed eyewitness — never shared with either the defense or the district attorney before the conviction — in which he said he had not seen Ms. Tyson with the victim.

“I feel that because I was Black, uneducated, naïve and a woman, I was very vulnerable,” Ms. Tyson said in a 2004 interview with LaVerne McQuiller Williams of the Rochester Institute of Technology that was published in the journal Women’s Studies Quarterly in 2004. “I was uneducated, so why not take this bitch off the street, and that’s what the police did. I was on the streets using drugs and selling my body and I had a criminal record.”

Ms. Tyson was born Betty Dove on June 29, 1948, in Rochester to James Dove, a laborer who apparently left the family when Betty was young, and Mattie Lawson, who worked in an auto parts factory and was often missing from the home where her eight children were living.

Betty started stealing when she was 8 and contracted syphilis at 13, about the same time she switched from Robitussin cough syrup to heroin. She dropped out of school at 14.

To escape her mother’s beatings, she married Arthur Tyson at 17; they divorced after six months. By then she had already been arrested 16 times for nonviolent crimes.

Prison might have permanently embittered her, but instead she found religion; cared for inmates with AIDS; received a general equivalency diploma; began an exercise program that earned her the nickname “the Jane Fonda of Bedford Hills”; became an accomplished chef; took photography classes, winning several competitions; and qualified as a printer’s apprentice.

“She had an ability to transform any situation, to turn poison into medicine, to turn pain into celebration, to find a way in any system to outsmart it and not be beaten down by it,” said V, the playwright formerly known as Eve Ensler, who had met Ms. Tyson when she taught writing at the prison.

Despite her outstanding prison record, Ms. Tyson was denied parole, as recently as two months before her conviction was overturned, because she had refused to take responsibility for a crime that she insisted she had not committed.

Ms. Tyson’s mother died six months after Ms. Tyson was released. In addition to her sister, she is survived by two brothers, Allan Hall and Alexander Lawson.

While Ms. Tyson lost a lawsuit against the state for wrongful imprisonment on a technicality, she received a $1.25 million settlement from the City of Rochester.

But she struggled with money and lent too much to irresponsible family members and friends. “It’s funny how many family members I had when I came out,” Mr. Getz, her lawyer, recalled her telling him. “I know who my real family was. They were the ones who called me and came and saw me when I was inside.”

She also lost a home to foreclosure, and she was unable to get jobs in fields for which she was trained, though at one point she made $143 a week cleaning a day-care center. In 2011, she was arrested on petty larceny charges for stealing a pair of scissors and a knife worth $32.50 from a supermarket. The charges were dismissed.

She had learned a great deal about herself in prison, she said, even if she was unable to apply it all once she was released.

“They can keep you there physically but not mentally,” Ms. Tyson told The New York Times in 1998. “You escape in your mind. When you look out the window, you have to look past the razor wire and see the trees.”

“I am a totally different person,” she added. “If I’d have stayed out in the street, I probably would have ended up dead — killed, overdosed or from AIDS. That doesn’t mean I’m grateful to have been in prison all this time. But I turned a negative to a positive. I found out who Betty Tyson was.”