Joe Biden’s White House physician on Wednesday declined to answer questions during a closed-door deposition with the House Oversight Committee, invoking his Fifth Amendment right as the Republican-led panel pushes forward in its probe of the former president’s mental fitness and decline.

Dr. Kevin O’Connor also invoked his rights under the Fifth Amendment to avoid answering questions during a House Oversight Committee probe into whether Biden was capable of serving as president.

Joe Biden’s White House doctor’s uncooperativeness in a House probe looking into the former president’s fitness to serve has led the Republican congressman overseeing the investigation to allege a “coverup” of Biden’s “cognitive decline.”