Hope Hicks, Donald Trump‘s former aide and White House communications director, will testify next at a closed-door House Judiciary Committee session, said Chairman of the committee Jerry Nadler (D- New York). A public transcript of the hearing will be released later.

Hicks, who was a longtime confidant to the president, will answer lawmakers’ questions as part of the House inquiry into whether or not Trump obstructed the investigation of former special counsel Robert Mueller. Hicks’ appearance before the panel will be the first time that a Trump aide, current or former, will testify before the House probe. The president has done his best to ensure that such an occurrence never happens, doing everything in his power to delay the investigation. He has repeatedly cited executive privilege, a concept which allows a sitting president to prevent the subpoena of their aids, as well lets them block the release of confidential documents. While Trump has successfully pressured many of his allies into not handing over information to the House Judiciary Committee, Hicks has both agreed to turn over documents to the panel, as well as provide her own testimony.

This is not Hicks’ first time testifying during such an investigation, however, as she played a key role in the Mueller investigation. Because she was present during many of the potential incidents of obstruction of justice that Mueller outlined in his report, her testimony was invaluable. She also went in front of the House Intelligence Committee while she was still White House communications director. During that hearing, Hicks admitted that she often told “white lies” for the president while serving in her official capacity.

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Hicks’ testimony comes as House Democrats speed up their various investigations into the president, eager to find some evidence that would allow them to begin impeachment proceedings against him. Nadler has been an especially vocal proponent of impeachment, coming out in support of the idea after Mueller’s statement confirming that he had not cleared Trump of any wrongdoing.