John Edward Smith, 37, who had been sentenced to life, gained his freedom after prosecutors conceded their star witness had perjured himself, the Los Angeles Times reported.
Smith insisted he was miles away at his grandmother's house at the time of the shooting involving the Crips and the Bloods.
Smith was ultimately cleared with help from the activist group Innocence Matters, which uncovered problems with the testimony of the lone witness to identify Smith as the gunman, the Times said.
The witness eventually recanted, leading Superior Court Judge Patricia Schnegg to vacate Smith's 1995 conviction, an action that drew cheers and applause from people in the courtroom.
Coincidentally, the Times noted, R&B singer Chris Brown was among those in the courtroom as he awaited his probation hearing. He joined in applauding the ruling in Smith's favor, the newspaper said.