There were dozens of witnesses when a gunfight broke out on a street corner in Buffalo on Aug. 10, 1991. Torriano Jackson, 17, was killed. Valentino Dixon, then 21, was at the scene. Hours later, he was arrested. And in 1992, he was convicted of murder and sentenced to almost 40 years to life in prison. For years, Mr. Dixon fought that conviction from behind bars, insisting on his innocence. No physical evidence had ever connected him to the murder, and another man had confessed to it more than once. His murder conviction was vacated on Wednesday, and Mr. Dixon, 48, walked free. As he struggled to get his conviction overturned, Mr. Dixon got help from ... Martin Tankleff, who was imprisoned for 17 years after being wrongly convicted of murdering his parents. In prison, [Dixon] liked to draw detailed landscapes in colored pencil. Golf courses were a frequent subject. That caught the interest of journalists at Golf Digest, and the magazine profiled Mr. Dixon. In 2017, a new district attorney, John Flynn, took office in Erie County. And in 2018, a course called the Prison Reform Project was offered for the first time at Georgetown University ... with Mr. Tankleff [serving] as an adjunct professor. Three students chose Mr. Dixon's case and gathered evidence. Their work helped Donald M. Thompson, a lawyer for Mr. Dixon, make his case to the district attorney's office. Mr. Flynn, the district attorney, said the newly discovered evidence from various witnesses attesting to Mr. Dixon's innocence was deemed credible.