“It is a sleeper case,” Harvard Law professor Alex Whiting said. “If the D.C. Circuit were to accept the Department of Justice’s arguments…that would have potentially enormous implications for the future of the information from the Mueller investigation. That could close out a path by which that information becomes public.”

The case at the appeals court was brought by attorney and author Stuart McKeever, who has spent decades investigating the disappearance of Jesus Galindez, a Columbia university professor and political activist who vanished in New York City in 1956. His body was never found, but there are indications that he was kidnapped and flown to the Dominican Republic, where he may have been killed.

McKeever, 82, wants a judge to release secret testimony given to a DC-based grand jury that investigated Galindez’s disappearance. But the Justice Department argues that judges don’t have “inherent authority” to release such information unless it falls under exemptions approved by Congress, which don’t apply in the Galindez case — or in many others, including potentially Mueller’s investigation.

“I’ve been on the journey almost 40 years to tell this story,” McKeever said Sunday in a phone interview from his South Carolina home. “The Justice Department does not want this case to break the dam.”

The arguments in McKeever’s case next month will take place at the D.C. Circuit Court of Appeals in Washington — two floors above where Mueller’s grand jury meets.

Adding to the political drama around the McKeever case: the judges drawn to decide it. The three-judge panel announced by the court last week leans Republican, which is unusual since most of the D.C. Circuit’s active judges are Democrats. In addition, the panel will include the appeals court’s only Trump appointee, Judge Greg Katsas. Also assigned to the case: Judge Douglas Ginsburg, a Reagan appointee, and Judge Sri Srinivasan, an Obama appointee.