The congressional committee investigating the attack on the US Capitol says Donald Trump may have engaged in criminal conduct in his bid to overturn his election defeat.
Charles Burnham, a lawyer for Dr Eastman, said his client was abiding by his ethical duty to protect client confidences.
"Because this is a civil matter, Dr Eastman will not have the benefit of the Constitutional protections normally afforded to those accused by their government of criminal conduct. Nonetheless, we look forward to responding in due course."Mr Trump has repeatedly called the Select Committee's inquiry a politically motivated investigation.
"Thanks to your bullshit, we are now under siege," the Pence lawyer, Greg Jacob, wrote to Dr Eastman. The filing shows Mike Pence was being pressured to try and stop Joe Biden's certification as US president.