No statutory crime is needed to impeach, Trump chose to not present his case or MATERIAL witnesses in the house, witnesses are not called to tell us their opinions on impeachment or crimes, they are called for evidence gathering purpose.The US Senate is well within its authority to dismiss this case based on the House's Impeachment, during which they presented no prosecutable crime, presented no evidence, presented no witnesses...those they had testify could not name 1 crime or Impeachable offense committed by the President when asked to do so.