They are obligated to make the court (the committee) aware of any exculpatory evidence. If Not they themselves can be held in contempt for withholding or even obstruction of justice.
Adumb has written his own obituary! There may not be any need to call him since he already has made his statement part of the public record. Calling him would just give him a chance to grandstand for his own audience. Instead they can just confirm that he initiated the order to place his statement in the record. (Ex 1) Then enter the Trump transcript as exhibit 2 of evidence Since it’s obvious he lied it’s a non contested charge. Guilty