The recent impeachment by the U.S. House of Representatives is an accusation that President Trump has committed high crimes — an accusation and nothing more.  By law, President Trump is presumed to be innocent of the accusation until proven guilty beyond a reasonable doubt of the alleged crimes in a court of law.  One of the world's oldest principles of jurisprudence, the presumption of innocence was first codified into Roman law under the sixth-century emperor Justinian: "Proof lies on him who asserts [in this case, the House] — not on him who denies [the president]."  The principle was based on Roman legal practices from the third century. 

The presumption of innocence is a cardinal principle of the United States justice system.  The Constitution's Fourth, Fifth, Sixth, Eighth, and Fourteenth Amendments all support the principle with express language to protect the accused.  The Sixth includes the right of the accused to a "speedy trial."  In Coffin v. United States, the 1895 Supreme Court ruled:

The principle that there is a presumption of innocence in favor of the accused is the undoubted law [of the United States], axiomatic and elementary.

This POI principle is further encoded in the legal systems of the United Nations under Article 11 of its Universal Declaration of Human Rights, as well in the constitutions and/or legal codes of every major country, including socialist China and Russia.

Thus, President Trump does not have to prove anything.  The burden of proof that crimes have been committed lies solely and entirely on the accuser, the House of Representatives. 

Democrats and the media would have us all believe that President Trump has in fact committed crimes, that he has violated the Constitution.  Nothing could be farther from the truth.  He has been accused, but neither accusation has been proven, nor has he been given a constitutionally mandated "speedy" trial.  By denying a speedy trial, the real violation of the Constitution has been and is being committed by the House of Representatives and its speaker.