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Washington CNN  — 

The Justice Department’s investigation into the White House documents seized from former President Donald Trump’s Mar-a-Lago resort is among the most politically explosive probes in recent years.

In the four months since the FBI’s search, the DOJ and Trump’s attorneys have repeatedly clashed in court over what documents can be examined and why.

The result has been a mixed bag. Trump’s team initially got the special master that they had pushed for, though his role is in question after an appellate court ruling, and the DOJ also appointed a special counsel – much to the former president’s chagrin.

Here’s what a special master is, what a special counsel is and what role each plays in the Mar-a-Lago investigation.

What is the role of the special counsel?

A special counsel is a lawyer appointed to lead an independent investigation and, if necessary, to prosecute anyone suspected of crimes. He or she must come from outside the government. A special counsel is typically appointed when the usual investigative bodies under the Justice Department, such as the FBI, have a conflict of interest in carrying out a probe.

Attorney General Merrick Garland appointed a special counsel to oversee the criminal investigations into the retention of national defense information at Trump’s Mar-a-Lago resort and parts of the January 6, 2021, insurrection.

“Based on recent developments, including the former president’s announcement that he is a candidate for president in the next election, and the sitting president’s stated intention to be a candidate as well, I have concluded that it is in the public interest to appoint a special counsel,” Garland said at the Justice Department on Friday.

Jack Smith, the former chief prosecutor for the special court in The Hague, where he investigated war crimes in Kosovo, will oversee the investigations.

Why did Trump oppose a special counsel?

Trump has sought to paint the investigations as politically motivated, including at his presidential announcement last week, where he said he was the victim of a “weaponization” of the justice system.

Speaking at the America First gala at Mar-a-Lago on Friday night, the former president called the special counsel appointment an “appalling announcement” and a “horrendous abuse of power.”

Trump’s lawyers had been dreading the prospect of a special counsel, concerned it could drag out the investigation they have fought continuously in court. And Trump himself has complained about the matter, likening the prospect to former special counsel Robert Mueller, who oversaw the Russia investigation.

The former president on Friday indicated that he had believed federal investigations into him were slowing down or over until the announcement from Garland. He repeatedly called the investigations political and said it was not a fair situation and would not be a fair investigation, telling the crowd at Mar-a-Lago, “You’d really say enough is enough.”

What is the role of the special master?

A special master is a third-party attorney appointed by a court to oversee part of a certain case.

The special master in the Mar-a-Lago case, Judge Raymond Dearie, was specifically tasked with overseeing the Justice Department’s review of the evidence gathered from Trump’s beach club and filtering out privileged material that may have been seized in the search.

But Dearie’s role was thrown into question when the 11th US Circuit Court of Appeals halted his review of documents seized from his Mar-a-Lago estate.

The ruling removed a major obstacle to the Justice Department’s investigation into the mishandling of government records from Trump’s time in the White House.

“The law is clear,” the appeals court wrote. “We cannot write a rule that allows any subject of a search warrant to block government investigations after the execution of the warrant. Nor can we write a rule that allows only former presidents to do so.”

The 11th Circuit said that either approach would be a “radical reordering of our caselaw limiting the federal courts’ involvement in criminal investigations” and that “both would violate bedrock separation-of-powers limitations.”

Trump’s legal team has not decided whether to appeal the ruling to the Supreme Court but is weighing the option, a source familiar with the discussions told CNN.

Why did Trump want a special master?

Trump’s legal team broadly argued that a special master is necessary to ensure the Justice Department returns any of his private documents seized during the search of Mar-a-Lago.

The former president’s attorneys said his constitutional rights were violated, and that there may have been privileged materials seized. But in court filings, Trump did not elaborate on what exactly he hoped a special master would filter out, besides general allusions to “privileged and potentially privileged materials.”

The Justice Department has already returned to Trump a selection of documents that were either legal in nature or were non-government records with sensitive personal information, like medical records.

At stake now is the more than 2,800 documents obtained in the search that Trump is fighting to keep out of the investigators’ hands.

Where does the Mar-a-Lago investigation stand?

Prosecutors are examining whether there was obstruction of justice, criminal handling of government records and violations of the Espionage Act, which prohibits unauthorized storage of national defense information.

As a reminder, the Mar-a-Lago probe burst into public view when the FBI executed a search warrant on Trump’s Florida resort in August.

Trump went to court to secure an order requiring that a third attorney review the materials seized in the search. Documents marked as classified were excluded from that review by an appellate court, allowing for their use in the criminal probe.

Investigators have also brought witnesses before a federal grand jury that has been empaneled in DC in the probe.

According to multiple sources, both the Mar-a-Lago investigation and the January 6 investigation around Trump are aiming to gather more information and bring witnesses into a federal grand jury in the coming weeks. Prosecutors sent out several new subpoenas related to both investigations in recent days, with quick return dates as early as this week.

This story has been updated with additional information.

CNN’s Tierney Sneed, Evan Perez, Ariane de Vogue and Angela Dewan contributed to this report.