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Nunberg caps off strange week with appearance before Mueller grand jury

Washington(CNN) Former Trump campaign aide Sam Nunberg arrived at District Court in Washington, DC, Friday morning, where he is expected to deliver federal grand jury testimony as part of special counsel Robert Mueller's investigation.

Nunberg is the first recognizable Trump campaign affiliate to appear at a grand jury hearing related to Mueller's investigation into Russian meddling in the 2016 election by walking through the main entrance of the federal courthouse and heading to the grand jury area. Other witnesses have presumably testified before Mueller's grand jury since it started meeting last July, but none have made as public an appearance.

Nunberg did not speak to the press outside the courthouse or on his way into the grand jury area Friday morning. He was accompanied by his lawyer, and a court marshal led them into the grand jury area at 9:30 a.m. ET.

Another previous grand jury witness, Jason Maloni, testified for Mueller's team in September about his work as a spokesman for former Trump campaign chairman Paul Manafort, and answered questions outside the courthouse.

Manafort was indicted by a grand jury in late October for foreign lobbying work and other business he conducted prior to his time leading the Trump campaign. He has pleaded not guilty to the charges and has a trial date set for July 10. Maloni still works for Manafort.

A secret proceeding

Mueller's grand jury appears to meet regularly, even weekly or more, in the federal courthouse in Washington. As with any federal grand jury, 16 to 23 individuals review the evidence and case overviews that prosecutors present to them, ask witnesses questions under oath, then decide whether prosecutors have enough evidence to bring a criminal case.

The grand jurors and prosecutors are bound by secrecy regarding what happens in their proceedings, though witnesses are able to speak about their interactions with a grand jury. No one but the witness, the jurors, prosecutors and limited courthouse staff such as translators are able to sit in on grand jury hearings. So, even though Nunberg's attorney accompanied him to the court Friday, the lawyer can't be in the grand jury hearing.

Ultimately, at least 12 grand jurors must approve the new indictments.

So far in the Mueller investigation, prosecutors have made public grand jury indictments against Manafort, his deputy Rick Gates and 13 Russians who allegedly used stolen identities to influence the presidential election through social media.

Nunberg had planned to defy subpoena

Nunberg brazenly declared earlier this week that he planned to defy a federal subpoena compelling his testimony, but he later backed down, pledging to CNN on Tuesday that he was "going to cooperate with whatever they want."

Nunberg was fired from the Trump campaign in August 2015 after a series of racist Facebook posts came to light.

He said Monday that he was refusing to cooperate with the subpoena because he believes investigators are trying to get him to impugn controversial Trump ally Roger Stone, who Nunberg called his mentor.

"They want me to say that Roger was going around telling people he was colluding with (WikiLeaks founder) Julian Assange," Nunberg said Monday.

During the 2016 campaign, Stone appeared to predict that WikiLeaks would soon release damaging information about Hillary Clinton, including stating that it would be Clinton campaign chairman John Podesta's "time in the barrel" ahead of the WikiLeaks' release of Podesta's emails.

The US intelligence community determined in January 2017 that Russian intelligence provided the hacked emails to WikiLeaks, which Assange denies.

As he has before, Stone denied on MSNBC Tuesday any collusion with Russia and said he "never had any advance knowledge of the content, the source, or the exact timing of the WikiLeaks disclosures," nor discussed the hacked emails with President Donald Trump. He also said he never talked about Clinton's emails with Trump.

CNN's Veronica Stracqualursi, Jeremy Diamond and Eli Watkins contributed to this report.