The burden would be on the individual if he uses “incompetence” as an affirmative defense. The burden would be on the accuser if the accusation made is “incompetence”. Problem is that if an accusation of incompetence has to be proven at hearing, you may not be able to call the individual to testify - you’re already claiming he is incompetent. You would need an expert that has examined the individual to testify. There are none existing that would testify to help the accuser as far as Biden goes.
Agreed, so this goes nowhere.