After voting to acquit Trump for inciting the insurrection, Republican Senate leader Mitch McConnell condemned the former president and called him "practically and morally responsible" for the riot. "President Trump is still liable for everything he did while he's in office. He didn't get away with anything yet," McConnell said.

Republicans have been anxious to get the trial over with and move on from discussion of Trump and the insurrection at the Capitol. Democrats, too, have a motive to move on since the Senate cannot move ahead on new President Joe Biden's agenda including Covid-19 relief while the impeachment trail is in session.

The vote on whether or not to convict the 45th president comes after a tumultuous morning in which prosecutors gave up a last-minute plan for witness testimony that could have significantly prolonged the trial and delayed a vote.

An unexpected morning vote in favour of hearing witnesses threw the trial into confusion just as it was on the verge of concluding. But both sides ultimately reached a deal to instead enter into the record a statement from a Republican lawmaker about a heated phone call on the day of the riot between Trump and House Minority Leader Kevin McCarthy that Democrats say established Trump's indifference to the violence.

The controversy was centred on whether to subpoena Jaime Herrera Beutler of Washington state, one of 10 Republicans to vote for Trump's impeachment in the House. She said in a statement late Friday that Trump rebuffed a plea from McCarthy to call off the rioters.

Democrats consider it key corroborating evidence that confirms the president's "willful dereliction of duty and desertion of duty as commander in chief". The situation was resolved when Herrera Beutler's statement on the call was read aloud into the record for senators to consider as evidence. As part of the deal, Democrats dropped their planned deposition and Republicans abandoned their threat to call their own witnesses.

The case then proceeded to closing arguments, where Democrats again alleged that Trump was responsible for the deadly January 6 siege on the day the Senate was certifying the election results. "He abused his office by siding with the insurrectionists at almost every point, rather than with the Congress of the United States, rather than with the Constitution," said lead House impeachment manager Jamie Raskin.

Raskin earlier said witnesses were necessary to determine Trump's role in inciting the riot. Fifty-five senators voted for his motion to consider witnesses, including Susan Collins of Maine, Lisa Murkowski of Alaska, Ben Sasse of Nebraska and Mitt Romney of Utah. Once they did, Lindsey Graham of South Carolina changed his vote to join them on the 55-45 vote.

Trump lawyers opposed calling witnesses, with attorney Michael van der Veen saying it would open the door to him calling about 100 of his own. He said the depositions could be done in his law office in Philadelphia, prompting laughter from senators.

"If you vote for witnesses," Van der Veen said, crossing his arms and then then raising them in the air for emphasis, "do not handcuff me by limiting the number of witnesses that I can have."

The outcome of the raw and emotional proceedings was reflecting a country divided over the former president and the future of his brand of politics. The verdict could influence not only Trump's political future but that of the senators sworn to deliver impartial justice as jurors.

"If we don't set this right and call it what it was, the highest of constitutional crimes by the president of the United States, the past will not be past," another impeachment manager, Madeleine Dean of Pennsylvania, told senators. "The past will become our future."

The nearly week-long trial has delivered a grim and graphic narrative of the riot and its consequences in ways that senators, most of whom fled for their own safety that day, acknowledge they are still coming to grips with.

House prosecutors have argued that Trump's rallying cry to go to the Capitol and "fight like hell" for his presidency was part of an orchestrated pattern of violent rhetoric and false claims that unleashed the mob. Five people died, including a rioter who was shot and a police officer.

Trump's lawyers countered in a short three hours Friday that Trump's words were not intended to incite the violence and that impeachment is nothing but a "witch hunt" designed to prevent him from serving in office again.

Only by watching the graphic videos — rioters calling out menacingly for House Speaker Nancy Pelosi and Vice President Mike Pence, who was presiding over the vote tally — did senators say they began to understand just how perilously close the country came to chaos.

Hundreds of rioters stormed into the building, taking over the Senate. Some engaged in hand-to-hand, bloody combat with police.

Many Republicans representing states where the former president remains popular doubt whether Trump was fully responsible or if impeachment is the appropriate response. Democrats appear all but united toward conviction.

Trump's lawyers have vigorously denied that the former president incited the riot and they played out-of-context video clips showing Democrats, some of them senators now serving as jurors, also telling supporters to "fight," aiming to establish a parallel with Trump's overheated rhetoric.

"This is ordinary political rhetoric," said van der Veen. "Countless politicians have spoken of fighting for our principles." Democratic senators shook their heads at what many called a false equivalency to their own fiery words.

Trump is the only president to be twice impeached and the first to face trial charges after leaving office.

Unlike last year's impeachment trial of Trump in the Ukraine affair, a complicated charge of corruption and obstruction over his attempts to have the foreign ally dig up dirt on then-campaign rival Biden, this one brought an emotional punch over the unexpected vulnerability of the US tradition of peaceful elections.