A federal trial is set to begin in Washington, D.C., on Tuesday, but unlike other trials that regularly take place in the national’s capital, the acquittal of the defendant, President Donald Trump, is all but guaranteed, and next to no one knows what the rules are.

Arguments will begin this week in an impeachment trial that presents a rare mix of legal and political proceedings. It’s already off to a banner start, with Friday’s announcement that former independent counsel Ken Starr and Harvard Law School’s Alan Dershowitz will represent Trump.