(WASHINGTON) — 
Dr. Kevin O’Connor, former President Joe Biden’s physician, didn’t answer questions when he briefly appeared before the House Oversight Committee on Wednesday for a closed-door, transcribed interview.

O’Connor was subpoenaed by Committee Chairman James Comer as part of a Republican-led investigation into Biden’s mental fitness and use of a presidential autopen while in office.

O’Connor’s lawyer, David Schertler, said in a statement that the doctor “asserted the physician-patient privilege, as well as his right under the Fifth Amendment to the U.S. Constitution, in declining to answer questions from the staff of the House Committee on Oversight and Government Reform regarding his service as Physician to the President during the Biden Administration.”

Comer also said the doctor continuously pleaded the Fifth Amendment — a right to refuse to answer questions where someone might incriminate themself.

“This is unprecedented. And I think this adds more fuel to the fire that there was a cover up,” the congressman said.

O’Connor didn’t take any questions from reporters when he arrived and left the Rayburn House Office Building on Wednesday morning.

Doctors have a legal obligation to not talk about things like patient interactions, diagnosis, and treatments. Sharing this information can lead to civil and criminal penalties, according to the Department of Health & Human Services.

The House Oversight Committee has requested interviews with several of Biden’s former White House aides in light of a reports questioning his mental fitness in his final year in office and alleged efforts by those around him to conceal it — allegations Biden has vehemently denied.

Neera Tanden, who served as the director of the White House Domestic Policy Council under Biden, sat for testimony in late June. When asked after by reporters if there was an effort to disguise Biden’s condition, Tanden replied: “Absolutely not.”

Comer said on Wednesday the GOP probe will continue.

“We have several other witnesses that are going to come in for transcribed interviews,” he said.

The White House waived executive privilege for O’Connor ahead of his appearance. The House Oversight Committee previously requested O’Connor and aides sit for interviews while Biden was president, but Biden blocked the request.

Months after leaving the White House, Biden was diagnosed with an aggressive form of prostate cancer.

Biden rejected reports of cognitive decline during an appearance on ABC’s “The View” in early May, before his office announced his cancer diagnosis.

“They are wrong. There’s nothing to sustain that,” Biden said at the time.

Former first lady Jill Biden, in the same interview, pushed back forcefully to accusations she shielded Biden from allies and the public.

“I did not create a cocoon around him. I mean, you saw him in the Oval Office. You saw him making speeches. He wasn’t hiding somewhere,” she said.

Since then, former president Biden has spoken at some events, including at the Society for Human Resource Management’s annual conference in San Diego last week, where he reflected on his leadership and career.

ABC News’ Eric Strauss contributed to this report.

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