'High crimes': See the moment Trump officially gets put on trial

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The Senate jurors for President Trump’s impeachment trial are officially sworn in by Chief Justice Roberts, taking an oath to do “impartial justice,” marking the beginning of the third impeachment trial of a president in U.S. history. MSNBC Chief Legal Correspondent Ari Melber analyzes the historical context of the monumental ceremony and a trial that “shows the system of checks and balances,” as President Trump prepares be judged for his alleged “high crimes.”