An elderly man who spent 24 years in prison for his daughter's death in a fire will remain free after a federal appeals court in Pennsylvania on Wednesday refused to reinstate his murder conviction.

Han Tak Lee, 80, a native of South Korea who earned U.S. citizenship, was exonerated and freed last year after a judge concluded the case against him was based on since-discredited scientific theories about arson. Prosecutors appealed, saying that other evidence pointed to his guilt.

The Philadelphia-based 3rd U.S. Circuit Court of Appeals rejected the appeal, meaning Lee will stay out of prison.

Lee said Wednesday in a brief phone interview that he was happy about the ruling. His attorney, Peter Goldberger, called on prosecutors to drop the case.

"I hope, now, that they will finally see there is no basis for this conviction," Goldberger said. "They can say it's nobody's fault, that science changed, that this is over now, and the federal court has had the last word."

Monroe County District Attorney David Christine, who prosecuted Lee in 1990, said he will consider an appeal to the U.S. Supreme Court.

"Although we are disappointed in the ruling, we know that the Court of Appeals gave very serious consideration to the arguments of all parties, and entered a decision only after careful and thoughtful scrutiny of all the relevant facts and legal issues," he said via email. "However, we remain convinced that in spite of the debunking of some of the (prosecution witnesses) on the cause and origin of fire accepted by the scientific community in the 1980s, the defendant's guilt was otherwise established by relevant and admissible evidence presented to the jury."

Lee's conviction was one of dozens to be called into question around the U.S. amid revolutionary changes in investigators' understanding of how an intentionally set fire can be distinguished from an accidental one.