() A third witness has pleaded the Fifth Amendment while testifying before House Republicans about former President Joe Biden’s mental acuity while in office.

Annie Tomasini, Biden’s former deputy chief of staff, invoked the protection multiple times during a closed-door deposition Friday, according to Rep. James Comer, R-Ky., chair of the House Oversight Committee.

Tomasini reportedly declined to answer questions about Biden’s health, his handling of classified documents and the first family’s alleged business dealings during the roughly 30-minute deposition.

On social media, Comer said the hearing was proof of a “pattern of key Biden confidants seeking to shield themselves from criminal liability for this potential conspiracy.”

“It’s unbelievable that Ms. Tomasini and others refuse to answer basic questions about President Biden’s fitness to serve,” Comer added. “It’s apparent they would rather hide key information to protect themselves and Joe Biden than be truthful with the American people about this historic scandal.”

Early this month, Biden’s White House physician, Dr. Kevin O’Connor, invoked his Fifth Amendment right and left his deposition shortly after arriving. Anthony Bernal, who previously served as chief of staff to former first lady Jill Biden, did the same last week.

The White House and Comer allege that Biden staffers helped cover up the former president’s mental decline at the end of his term in office.  Both Biden and Bernal have rejected those accusations.

The former president shared similar sentiments during an interview published Sunday by the New York Times, telling the outlet: “I made every decision.”

There are four additional depositions on deck in the coming months, featuring testimony from Ian Sams, former special assistant to Biden; Andrew Bates, former deputy assistant to Biden; Karine Jean Pierre, former White House press secretary; and Jeff Zients, former White House chief of staff.

NewsNaion partner The Hill contributed to this report.