Following the search of his Mar-a-Lago home, former President Donald Trump has asked the courts to appoint a “special master” to review the documents obtained during the search. According to the Associated Press, a federal judge is planning to do just that.

However, it could be too late. The Justice Department said Monday that it has already completed a review of the documents.

Trump’s legal team wants independent oversight over the materials removed to see if anything should be covered by executive privilege and to ensure that any documents that fall outside the scope of the search warrant are returned to the former president, the AP said. U.S. District Judge Aileen Cannon revealed Saturday that she’s inclined to side with Trump and appoint an independent special master. She also told the DOJ to file more in-depth descriptions of the material taken from the former president’s home “specifying all property seized.”

So, what is a special master? And what impact would one have on the investigation?

A special master is an independent person, often a retired judge, tapped by the court to oversee potentially complex or highly sensitive cases. Special masters help quell disputes, set through materials to address technical issues, ensure investigators do not get into privileged matters, review and organize information and prepare reports for the presiding judge, the McCammon Group, a neutral dispute resolution firm in Virginia, explained on its website.

Reporting on the Trump case, Politico reported that the appointment of a special master in these types of situations is uncommon, though, as the outlet noted, it notably happened in two high-profile investigations of a pair of Trump’s former lawyers: Michael Cohen and Rudy Giuliani.

According to the AP, a special master would unlikely impact the direction of the DOJ’s investigation of Trump’s possession of documents containing some of America’s most closely held secrets. However, it is possible that the independent reviewer could cause the probe to slow down.