The witness is a former attorney of P. Trump’s. He made a post at Truth Social naming names. I came across the name in another thread here at FR, moments ago.
I think it is Costello, because a poster commented that P. Trump should try to get Governor Abbott, of TX, involved somehow, for the obvious reason that humor or mocking would be inserted into the absurdity of it all.
check here.
https://www.insider.com/surprise-trump-grand-jury-witness-is-giuliani-lawyer-robert-costello-2023-3
costello was Cohen’s legal advisor and before that he worked for Giuliani
it appears Cohen is the rebuttal witness to Costello.
If an indictment hinges on these 2 witnesses, then, after all this time, they got nothin.