A man who spent more than two decades in prison for murder was set free Tuesday by a judge who said his trial was deeply flawed. Rosean S. Hargrave was convicted in 1991 after being investigated by Det. Louis Scarcella, who the Brooklyn District Attorney’s Office found once framed an innocent man. Several convictions stemming from Scarcella’s work have since been thrown out. No new evidence against Hargrave has emerged in the years since he went to prison and, according to the judge, “potentially exculpatory evidence” had been destroyed.