Also: Hundreds of arrests have been made, with many rioters claiming both during and after the incident that they believed Trump had summoned them to take illegal action to stop the counting of Electoral College votes for Joe Biden. House impeachment managers could call one or more of them to testify, perhaps in exchange for leniency, to make the case that there was a connection between Trump’s speech and their violence. This could be important, since Trump’s lawyers now claim that “the people who criminally breached the Capitol did so of their own accord and for their own reasons.”

Witness testimony could directly counter that assertion.

But witness testimony would also shore up the first prong of a criminal incitement charge, assuming for argument’s sake that the test applies here: That Trump intended his words to have the effect of stoking lawlessness. One aide reportedly described Trump’s behavior during the siege as that of “a total monster.” Another called him “insane.” The New York Times’ Maggie Haberman reported that “[h]e was pleased because he liked the scene.” Senator Ben Sasse said in an interview that he has had conversations with senior White House officials and was convinced that Trump “wanted there to be chaos.” And disavowals notwithstanding, it looks like the Trump campaign was involved in organizing the January 6 rally that erupted in violence.

Calling Trump’s former staff to testify as to his knowledge and state of mind could produce a powerful trial record that goes directly to one of the two main legal questions about his incitement.