I don’t know if there are rules set in stone. I’ve heard tv law professors say that they can make up the rules as they go along. All they go by is tradition and/or precedent.
Well the precedent the Dems are setting is destroying this Constitutional Republic and any rule of law therein.
But due process is cast in the stone of the constitution and so Trump can take them to court for constitutional reasons. So they can make the rules for the House, and the Senate can make rules for the senate too. But skipping things like the right to cross examine a witness or holding hearings in secrecy will not fly when it gets to court.
That's true, but the "they" is the House of Representatives, as stated in the Constitution. It's not Nancy, the Speaker, nor is it committee chairmen, it's the entire House. That can only happen with votes. The exact words from the constitution on impeachment are: “The House of Representatives shall chuse (sic) their Speaker and other Officers; and shall have the sole Power of Impeachment.”