Attorneys for a U.S. Air Force veteran accused of leaking classified information about Russian hacks targeting state election boards have signaled they will challenge whether the document in question truly contained classified national defense information.

Reality Winner’s defense this week notified federal prosecutors they intend to call J. William Leonard—the U.S. government’s former “classification czar”—as an expert witness at a trial scheduled to begin in October. Leonard served as director of the U.S. Information Security Oversight Office from 2002-2008.