One day after the death of Rubin 'Hurricane' Carter, a former professional boxer who spent nearly 20 years in prison for a triple murder he didn't commit, the other man convicted with him described him as "David to the Goliath of the judicial system."

John Artis, who was wrongfully convicted alongside Carter for the June 17, 1966 murders of three people in Paterson, N.J., has been friends with Carter since the two were arrested that night.

When Carter was diagnosed with prostate cancer in 2012, Artis moved to Toronto to care for his friend. Artis said it was a "no-brainer" for him to drop everything so he could be at Carter's side. He was with the 76-year-old Carter when he died on Apr. 20.

Artis still remembers the moment the jury delivered their guilty verdict. "That was the most frightening moment of my entire life," Artis told CTV's Canada AM.

The two men were convicted in 1967 after a trial based largely on the testimony of two petty criminals, one of whom later recanted.

The conviction was overturned in 1985, after a long campaign championed by the likes of Bob Dylan and boxer Muhammad Ali saw the case reopened.

Artis spent 14 years in jail before being released on parole in 1981, four years before the case was overturned. Carter ended up spending nearly 20 years behind bars before he was cleared.

Like Carter, Artis became a social activist upon his release. While Carter worked to help the wrongfully accused, Artis dedicated his life to helping at-risk youth.

"Once you have something like that, a traumatic instance like that, happen to you, what you really want to do is fight against it," said Artis.

On the night they were arrested in 1966, Artis and Carter fit the eyewitness description of two black men driving in a white sedan. They were actually stopped twice that night - once with a third passenger in the car, then again after the passenger had been dropped off.

That's when police took them into custody and brought them to the crime scene.

Artis described that moment as "the ultimate beginning to the nightmare."

Artis and Carter were acquaintances at the time they were arrested, but once convicted, Artis said he and Carter became partners.

"We were sort of joined at the hip," Artis said. "We've always cared for each other and provided for each other."

After their arrest, Artis said police offered him the chance to put all the blame on Carter, but Artis refused. "I told them that my parents didn't teach me to lie. I'm not going to lie for you," he said.

Artis said Carter was a fun-loving person away from the public eye.

"Rubin is a guy that had a heart of gold," said Artis.