After six days of carefully choreographed oral arguments, President's Donald Trump's impeachment trial is about to enter a volatile new phase as senators are allowed to ask whatever they want of House prosecutors and White House lawyers.It is a moment of opportunity — and peril — for both parties, as 100 senators engage in as many as 16 hours of questioning over two days of the House impeachment managers and Trump’s legal defence team that could shape the endgame of the trial.