A majority of the US Senate has voted that Donald Trump's impeachment is constitutional.
Senators gathered in the Capitol building on Wednesday morning (NZ time) to debate whether the constitution allows for prosecution of a US President once he leaves office. Donald Trump finished his four-year term in the White House on January 20 after Joe Biden was inaugurated.
After four hours of debate, the Senate voted 56-44 that the trial is constitutional.
All Democrats voted in favour. They were joined by six Republicans; Susan Collins of Maine, Bill Cassidy of Louisiana, Lisa Murkowski of Alaska, Mitt Romney of Utah, Ben Sasse of Nebraska, and Pat Toomey of Pennsylvania.
The trial has now adjourned for the rest of the day and the full impeachment trial will begin on Thursday morning (NZ time).
It's not yet known how long it will take before a decision will be made on whether the Senate convicts Trump of inciting an insurrection, although many people believe it will be much shorter than the three weeks it took last time he was impeached.
It's not yet clear if the legal teams will bring in witnesses as the Senators themselves were witnesses to the Capitol riots.
During Wednesday's proceedings, the House impeachment managers, who are arguing for Trump's conviction, presented Senators with a video from the Capitol riots on January 6.
It interspersed images of the January 6 Capitol violence with clips of Trump's incendiary speech to a crowd of supporters moments earlier urging them to "fight like hell" to overturn his election defeat.
Senators watched as screens showed Trump's followers throwing down barriers and hitting police officers at the Capitol. The video also included the moment when police guarding the House chamber fatally shot protester Ashli Babbitt, one of five people including a police officer who died in the rampage.
The mob attacked police, sent lawmakers scrambling for safety and interrupted the formal congressional certification of President Joe Biden's victory after Trump had spent two months challenging the election results based on false claims of widespread voting fraud.
"If that's not an impeachment offense, then there is no such thing," Democratic Representative Jamie Raskin, who led the prosecution, told the assembled senators after showing the video.
He wept as he recounted how relatives he brought to the Capitol that day to witness the election certification had to shelter in an office near the House floor, saying: "They thought they were going to die."
In contrast to the Democrats' emotional presentation, Trump's lawyers attacked the process, arguing that the proceeding was an unconstitutional, partisan effort to close off Trump's political future even after he had already departed the White House.
"What they really want to accomplish here in the name of the Constitution is to bar Donald Trump from ever running for political office again, but this is an affront to the Constitution no matter who they target today," David Schoen, one of Trump's lawyers, told senators.
He denounced the "insatiable lust for impeachment" among Democrats before airing his own video, which stitched together clips of various Democratic lawmakers calling for Trump's impeachment going back to 2017.