They could try charging him with a felony, for example 18 U.S.C. 1001 (lying to federal agents) - they might claim he was intentionally trying to deceive them i

They could try charging him with a felony, for example 18 U.S.C. 1001 (lying to federal agents) - they might claim he was intentionally trying to deceive them into thinking he was some nefarious character when he actually wasn’t, thereby wasting their investigative resources meaning they couldn’t spend that time chasing the real “bad guys”. Maybe the prosecution won’t succeed, but they could always use it to make his life hell for a few months then move to dismiss. As a surgeon, he might not be allowed to practice his job while felony charges are pending.