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.

Read More