Glenn Ford, 64, had been on death row since August 1988 over the death of 56-year-old Isadore Rozeman, a Shreveport jeweller and watchmaker for whom Mr Ford had done occasional yard work. Mr Ford always denied killing Mr Rozeman.
Mr Ford walked out the maximum-security prison at Angola and, as he walked away from the prison gates, said: "It feels good, my mind is going in all kind of directions. It feels good."
He said he did harbour some resentment at being wrongly jailed: "I've been locked up almost 30 years for something I didn't do.
"I can't go back and do anything I should have been doing when I was 35, 38, 40, stuff like that."
State district judge Ramona Emanuel took the step of voiding Mr Ford's conviction and sentence based on new information that corroborated his claim he was not present or involved in Mr Rozeman's death, his lawyers said.