WATCH: Jan. 6 committee Chairman Bennie Thompson introduces former White House aide as key witness

Cassidy Hutchinson, an aide in Donald Trump’s White House, is making a surprise appearance Tuesday before the House committee investigating the Jan. 6, 2021, insurrection — an effort by the panel to provide new details about Trump’s inner circle as he fought to overturn his election defeat.

Watch Thompson’s remarks in the player above.

“Thanks to the courage of several individuals, the truth won’t be buried, the American people won’t be left in the dark,” Thompson said in his opening statement on June 28.

The 25-year-old, who was a special assistant and aide to former Trump chief of staff Mark Meadows, has already provided a trove of information to congressional investigators and has sat for multiple interviews behind closed doors.

READ MORE: Who are the witnesses testifying at the Jan. 6 hearings?

But the committee called the hearing this week to hear her public testimony, raising expectations for new revelations in the nearly yearlong investigation.

Mississippi Rep. Bennie Thompson, the committee’s chairman, said the panel called the hearing in light of “specific detailed information about what the former president and his aides were doing and saying in those critical hours.”

Her appearance has been cloaked in extraordinary secrecy.

The committee announced the surprise hearing with only 24 hours’ notice, and Hutchison’s appearance was only confirmed to The Associated Press by a person familiar with the matter.

Support PBS NewsHour: