Rubin (Hurricane) Carter, a professional boxer who served nearly 20 years in prison in New Jersey after being wrongfully convicted of a 1966 triple murder, became an international figure after his release as an advocate for others jailed for crimes they did not commit.

Mr. Carter, a cause célèbre in the 1970s whose plight was dramatized in an eight-and-a-half-minute song by Bob Dylan and later in a 1999 movie starring Denzel Washington, died on Sunday in Toronto after a battle with prostate cancer. He was 76.

His long-time friend John Artis, who was also wrongly convicted with Mr. Carter for the same crime in 1966, confirmed the death in an e-mail to The Globe. Mr. Artis had been caring for Mr. Carter over the past three years as his condition worsened.

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While seen by many as an inspiring figure after his 1985 release, the Hurricane cultivated a much more menacing persona when he took up pro-boxing as a middleweight in 1961, with his fighting style of quick punches earning him his nickname.

His background matched the image. He had served more than four years in prison for assaults and robberies. At age 12, after assaulting a man he claimed was a pedophile, he was sent to a reformatory, from which he would escape. He had also spent two years in the army, serving in West Germany, where he got into boxing.

Born on May 6, 1937, in Clifton, N.J., Mr. Carter says he was bullied about his stammer, forcing him early on to learn to respond with his fists.

The story of the Hurricane later put into song and film begins on June 17, 1966. In the early morning hours, two black men shot and killed the bartender and two white patrons, one man and one woman, of the Lafayette Bar and Grill in Paterson, N.J.

Riding in his car nearby, after a night spent at local nightclubs, was Mr. Carter, then 29. Actually at the wheel that night, because Mr. Carter had been drinking, was Mr. Artis, a 19-year-old acquaintance who had hitched a ride from a bar. Another man was also with them in the car.

Looking for the suspects, police pulled them over, but let them go, since they were looking for two black men, not three. They were stopped again about 10 minutes later after the other man had been dropped off.

Police took them to the scene of the crime, and then to the hospital where a survivor of the attack who had been shot in the head was asked if they were the killers, and did not identify them. The initial descriptions given by witnesses did not match Mr. Carter and Mr. Artis. They were interrogated, given lie detector tests and released. A grand jury would later fail to indict them.

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But in October, police arrested both men and charged them with the murders. At their 1967 trial, an all-white jury would convict them based largely on the testimony of two local petty criminals, Alfred Bello and Arthur Dexter Bradley.

Mr. Bello, who robbed the register at the Lafayette Bar and Grill after the shooting, was standing lookout while Mr. Bradley was breaking into a nearby factory. While initially failing to identify Mr. Carter and Mr. Artis at the scene, both told police later that Mr. Carter was one of two black men they saw running from the bar.

While in jail, Mr. Carter published his 1974 book The Sixteenth Round, pounded out on an Underwood in his prison cell, and sent it to celebrities, including Muhammad Ali – who he knew from his boxing days and who would put up his bail before his second trial – a well as Stevie Wonder, Aretha Franklin, Harry Belafonte and Bob Dylan.

Mr. Dylan soon met with Mr. Carter -- "I recognized the fact that here was a brother," Mr. Carter would say of the Sixties icon, according to Rolling Stone – and helped organize two benefit concerts. With theatre director Jacque Levy, Mr. Dylan wrote the song Hurricane in 1975 that made Mr. Carter's story widely known.

The prosecution's two main witnesses, Mr. Bradley and Mr. Bello, would both recant their testimony, leading to a second trial in 1976.

But controversy would still dog Mr. Carter. He faced allegations that he assaulted a female supporter in a hotel room while on bail, allegations his lawyers denied. Authorities would decline to lay criminal charges in the case.

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Two witnesses that provided alibis for Mr. Carter also recanted, saying they had been encouraged to lie at the 1967 trial. Hopes for Mr. Carter and Mr. Artis soon faded. Mr. Bello recanted his recantation, reverting to his testimony from the first trial that labelled Mr. Carter as the killer.

In arguments that were not made in the 1967 trial, the prosecution also argued that the killings were a "racial revenge" plot, meant to avenge the death of a black tavern owner who was the stepfather of a friend of Mr. Carter.

A jury, this time with two black jurors, once again convicted Mr. Carter and Mr. Artis of first degree murder. Mr. Carter went back to his bare five-foot-by-seven-foot cell at Trenton State Prison, where he continued to refuse to take part in prison activities or eat prison food, saying that doing so was tantamount to admitting his guilt.

He relied instead on a supporter to bring him canned soups and vegetables that he cooked on an electric coil. According to a report in the New York Times in 1977, a year after his second conviction, none of the rock stars or celebrities drawn to his cause before the trial had come to visit him. He became estranged from his wife and two children.

In 1979, an illiterate black teenager named Lesra Martin, who had been plucked from his home in Brooklyn by a Toronto-based commune that wanted to help him learn to read and write, picked up a copy of The Sixteenth Round.

He became fascinated by Mr. Carter, and learned to read partly by going through the documents in his case. At his urging, others in the commune decided to try to help the former fighter gain his freedom, moving down to New Jersey to be close to him. They became known as "the Canadians," in the various retellings of Mr. Carter's life story.

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Mr. Martin, now a lawyer in Kamloops, B.C., said in an interview that he never doubted Mr. Carter's innocence, ever since the first time he met him in 1980, standing in the intimidating visitor room at a maximum security prison at just 16 years old.

"I am petrified as I am standing there waiting for him to come, and all of a sudden, he comes up and he realizes that I am shaking and I am scared and he begins to embrace me, and hug me, and whisper in my ear and tell me not to be afraid," Mr. Martin said. "My heart told me, unequivocally, at that point, that is not the heart of someone that could murder three people."

Mr. Carter's principal lawyers, Leon Friedman and Myron Beldock, with research assistance from the commune members, won a last-ditch hearing for their client, after all his other appeals were exhausted. They sought a writ of habeas corpus, a legal move that would have him set free for constitutional violations at his trial. (Mr. Artis had been paroled in 1981.)

On November 7, 1985, U.S. federal judge H. Lee Sarokin sided with Mr. Carter, saying the prosecution failed to disclose Mr. Bello's lie detector tests, which raised serious questions about his recanted testimony, and wrongly pursued what he declared a prejudicial "racial revenge" theory.

"The extensive record clearly clearly demonstrates that [Mr. Carter's and Mr. Artis's] convictions were predicated upon an appeal to racism rather than reason, and concealment rather than disclosure," wrote the judge, who was greeted each year afterward on the anniversary of his ruling with a phone call of thanks from Mr. Carter.

After prosecutors declined to press charges a third time, Mr. Carter was finally free and moved to Toronto to live with the commune and Mr. Martin. He married commune leader Lisa Peters, but by the early 1990s, the marriage crumbled. He then broke with the commune, bucking at its control over him after so many years in jail. Friends say he needed to stand on his own two feet. He also struggled with alcohol, a substance the commune did not allow.

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He moved in with Mr. Martin, then attending university, and the younger man was amazed at how out-of-touch nearly 20 years of incarceration had left Mr. Carter. He had never used voice mail, Mr. Martin said, or a bank machine. A passionate, preacher-like orator, Mr. Carter made money on his speaking engagements.

Before he broke with the commune for good in the early 1990s, Mr. Carter and the Canadians got involved in the beginnings of the Association in Defence of the Wrongly Convicted.

Toronto lawyer James Lockyer was fighting to free Guy Paul Morin, a Toronto-area man wrongly convicted of raping and murdering a nine-year-old girl, and Mr. Carter and the commune also got involved.

Mr. Carter would become the association's executive director. For the next 11 years, he was the front man for its efforts to free those jailed for crimes they did not commit. He and Mr. Lockyer would become close friends.

Mr. Lockyer remembers getting a call from Mr. Carter in 1999, when the ex-boxer was with Bill and Hillary Clinton in the White House for a special screening of Hurricane, the film by Canadian director Norman Jewison. Mr. Carter wanted to know if he should lobby the president to intervene in the case of a woman on death row in Vietnam that the association was trying to help.

But in 2004, Mr. Carter would resign from the association in anger, and break off all contact with Mr. Lockyer. He had demanded that the association do more to protest the appointment of the prosecutor behind Mr. Morin's conviction as a judge

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Fire would consume Mr. Carter's rented west-end house while he was on vacation that same year. He had no insurance, and was forced him to move to a basement apartment for a time.

He soon started his own small organization, Innocence International, to fight for prisoners he felt were wrongly convicted. And he wrote a 2011 memoir entitled Eye of the Hurricane: My Path from Darkness to Freedom, that featured a foreword by Nelson Mandela.

Mr. Carter was diagnosed with terminal prostate cancer in 2011. Mr. Artis, who had remained his friend ever since that night in 1966, dropped his life in Virginia to come to Toronto and care for Mr. Carter, after learning that his old friend was dying with no family at his side. He said Mr. Washington, whose portrayal of Mr. Carter was nominated for an Oscar, kept in touch, phoning Mr. Carter at Christmas time, for example.

Even as his health deteriorated, he sent a letter to the New York Daily News in February demanding the release of Brooklyn man David McCallum, whom Mr. Carter said was wrongly convicted of murder and jailed in 1985 -- the year he was released -- with no evidence.

"I am now quite literally on my deathbed and am making my final wish, which those in authority have the power to grant," the letter reads, adding that Mr. Carter will be surprised if he sees heaven after his death. "To live in a world where truth matters and justice, however late, really happens, that world would be heaven enough for us all."

Editors note: An earlier version of this article featured a headline that incorrectly spelled Mr. Carter's first name. This version has been corrected.