Roberts slams impeachment managers, defence

US Chief Justice John Roberts drew little attention to himself in the beginning 12 hours of his first impeachment trial. But it was just before 1 a.m., as tempers on the floor had started to wear thin, that he reminded senators, House impeachment managers and US President Donald Trump's defence team who was in charge.

“I think it is appropriate at this point for me to admonish both the House managers and the president's counsel in equal terms to remember that they are addressing the world's greatest deliberative body," Roberts said, after a particularly tense exchange between House Judiciary Committee Chairman Jerrold Nadler and the president's lawyers.

Roberts asked them to “avoid speaking in a manner and using language that is not conducive to civil discourse.”

He did not say what prompted his comments, but they came after Nadler told senators that voting to deny certain witnesses in the trial, as many Republican senators had, was a “treacherous vote” and a vote against the United States. Trump's defence team then said Nadler should be embarrassed and should apologize to the president and the American people.

Roberts' new role presiding over the trial is one of two jobs he is juggling as the impeachment session gets underway. On Tuesday morning, he donned his black robe and oversaw two arguments at the Supreme Court before heading across the street to the U.S. Capitol where he is presiding over the trial in the Senate chamber. His busy schedule meant he didn't have time to join his fellow justices for a group lunch, a high court custom following arguments.

He was scheduled to be back again in court on Wednesday morning - just hours after the first day of the trial adjourned at 2 a.m. ET (0700G).