About two weeks ago, an investigative file that had long been sought by defense lawyers was found in a box in a hallway at police headquarters. The file included witness statements that contradicted accounts that Mr. Thomas was involved. “Had that information been available at trial — and had the story of Shaurn’s presence in court at the moment the murder was committed been told correctly — prosecutors agreed the trial would likely have ended differently,” the Pennsylvania Innocence Project said in a statement. How the file got lost and was finally found was not clear. A department spokesman on Thursday said no one was immediately available to address those questions. Mr. Thomas, who studied cooking while in prison, was greeted by friends and relatives when he was released on Tuesday and headed to Red Lobster for dinner. Mr. Thomas’s legal issues are not quite over. Prosecutors could still seek a retrial on the charges, though his lawyers said that is unlikely. In a statement, Kathleen E. Martin, the first assistant district attorney, said a decision would be made “in the very near future.” “Our role is to seek justice at every opportunity and whether it be prosecuting violent criminals or reviewing cases to ensure those behind bars deserve to be there, we will carry out this duty fairly and thoroughly,” the statement said. The Philadelphia Inquirer and Daily News reported in November that the Conviction Review Unit had not found a single case worthy of overturning, while similar units in Dallas and New York City had exonerated dozens of inmates. The Philadelphia unit announced a restructuring and hiring of new staff members in February. Many questions remain about how Mr. Thomas’s case was investigated and prosecuted, Ms. Bluestine said. “That it took 24 years to get him out of prison should shame everybody,” she said.