Through forensics work on the court docket for the D.C. Circuit Court of Appeals and some eagle-eyed reporting at the D.C. federal courthouse, Politico has identified a secret grand jury court fight that appears to be related to special counsel Robert Mueller’s investigation.

The “Grand Jury Subpoena” matter, as its called on the docket, appears to have originated from the court of U.S. District Judge Beryl Howell, the chief judge in DC federal court, who has already heard other legal squabbles over whether certain witnesses must testify in front of Mueller’s grand jury.

Sometimes, like the fight over whether Paul Manafort’s attorney had to testify, the proceedings happen under seal — meaning the press and public can’t access them — and are later unsealed when the secrecy is no longer necessary. The challenge that Roger Stone’s aide Andrew Miller has brought to a grand jury subpoena started under seal but has since been allowed to spill into the public eye, with a November appellate court hearing on it expected to be open to the public.

The latest grand jury matter appears to have been appealed twice, the first time after a ruling from Howell on Sept. 19. An appeal was filed in front of the D.C. Circuit Sept. 24, but that appeal appears to have been denied on the basis of being premature.

The case’s proceedings in front of Howell remain under seal, but there’s a publicly viewable docket for it at the appeals court level, though none of the individual filings are accessible to the public and there’s no indication who the parties are.

One hint that it may be a Mueller-related issue that Politico picked up on is that appellate Judge Greg Katsas is not participating, per the docket for the first appeal. Before his appointment to the court, Katsas was a deputy White House counsel for President Trump and during his confirmation hearing, acknowledged he may have to recuse himself of Russia probe related matters.

Adding to Politico’s suspicions that it’s Mueller related is that one of its reporters spotted a man in the appeals court clerk’s office on the day of deadline for a filing in the secret case who asked the clerk for the special counsel’s most recent filing. He said, according to Politico, that he needed it for his law firm to write its response, but the man declined to identify himself when approached by Politico. Another filing was submitted in the sealed case later that day, according to Politico.

An appeals court hearing is set in the case for Dec. 14

Read the Politico report here.