The House Oversight Committee’s first closed-door, transcribed meeting investigating former President Joe Biden's mental acuity began Tuesday with former White House Domestic Policy Council Director Neera Tanden appearing for questioning on Capitol Hill.

The White House counsel Tuesday said ex-Biden aide Neera Tanden is not shielded by executive privilege and thus must provide “unrestricted testimony” on former President Joe Biden’s mental acuity. The decision was issued before Tanden appeared before the GOP-led House Oversight Committee for closed-door testimony Tuesday to give insights for the panel’s investigation of Biden’s cognition and use of autopen.

Dr. Kevin O’Connor, the former White House physician who treated then-President Joe Biden, will appear for a deposition before the House Oversight Committee on July 9, a source familiar with the committee’s schedule confirmed to NBC News.