Updated on Friday at 2 p.m. ET
Former President Donald Trump made history when he became the first president to be impeached twice by the House of Representatives. Roughly a year ago, the Senate acquitted Trump on two articles — abuse of power and obstruction.
This time, he faces one article approved by the House that argues he incited an insurrection at the U.S. Capitol on Jan. 6, the day that Congress was required by the Constitution to count and certify the electoral votes in the 2020 election.
Here's how the trial is expected to work
In a proceeding like this, House impeachment managers act as the prosecution, making their case of Trump's culpability to the senators, who act as jurors. House Speaker Nancy Pelosi, D-Calif., selected nine Democrats to serve as managers. Trump has his own defense lawyers.
On Jan. 25, the House managers delivered the article of impeachment to the Senate, which triggered the start of a trial.
Senate Majority Leader Chuck Schumer and Senate Minority Leader Mitch McConnell agreed last month to give the former president's defense team some time to prepare and established a schedule for filing pretrial briefs. The managers submitted their 80-page brief on Feb. 2 and the former president's defense team filed its own pretrial brief on Monday.
Schumer and McConnell agreed to a resolution that sets up the structure of the trial. Schumer said it will ensure a "fair and honest" process.
In a statement sent by Trump's office Monday, Trump's legal team said it was pleased there was bipartisan support on structuring the trial.
"This process will provide us with an opportunity to explain to Senators why it is absurd and unconstitutional to hold an impeachment trial against a private citizen," it read.
What is the timing for the trial?
On Tuesday, impeachment managers and the president's counsel had up to four hours equally divided to debate the constitutionality of the trial.
After the arguments, the Senate voted it had the jurisdiction to try the former president with a vote of 56 to 44, with six Republicans breaking with their party to join Democrats. The threshold to pass was a simple majority of 51 votes.
The trial proceeded at noon ET Wednesday with up to 16 hours for each side — or up to eight hours over two days — to present its case. However, both sides needed less than that by week's end, with managers taking two days but about five hours short of their allotted time and Trump's lawyers using only about three hours of their time on Friday.
Now that the presentations are done, senators have up to four hours to question both sides. Then there will be four hours divided equally between the parties for arguments on whether the Senate will consider motions to subpoena witnesses and documents, if requested by the managers.
The impeachment managers have already said that the senators themselves, who were sitting in the chamber the day of the Jan. 6 attack, are witnesses. Most lawmakers on both sides say adding witness testimony would prolong the trial unnecessarily.
There will be up to four hours equally divided for closing arguments, along with deliberation time if requested by the senators before the vote takes place.
Who is defending Trump?
David Schoen and Bruce Castor Jr. were named as Trump's lawyers after five members of his defense team reportedly left a little more than a week before the trial. Michael van der Veen was also later brought in.
Castor is the former county commissioner and former district attorney for Montgomery County, Pa. He's known, in part, for a case that he didn't pursue, declining in 2005 to prosecute Bill Cosby.
Schoen has worked briefly as counsel for Trump's longtime friend Roger Stone.
He is also linked to Jeffrey Epstein, the disgraced financier and convicted sex offender. In 2019, Schoen told the Atlanta Jewish Times that he met with Epstein in prison days before Epstein hanged himself.
Van der Veen, an attorney specializing in personal injury and criminal defense, has the lowest public profile of the team but took up a significant portion of defense time on Friday.
Will Trump testify?
Rep. Jamie Raskin, D-Md., the lead impeachment manager, sent a letter to Trump on Feb. 4 inviting the former president to testify under oath.
Trump's attorneys responded by calling the request a "public relations stunt."
Jason Miller, a senior adviser to Trump, told NPR's Domenico Montanaro that Trump would not testify, labeling the trial an "unconstitutional proceeding." A year ago, Trump also declined to participate personally in his first impeachment proceedings.
What are the two sides arguing?
In their brief, House managers said Trump is "singularly responsible" for the violence that ensued at the Capitol after rallying his supporters.
"To protect our democracy and national security — and to deter any future President who would consider provoking violence in pursuit of power — the Senate should convict President Trump and disqualify him from future federal officeholding," it reads.
They followed that brief with a dramatic two-day presentation before senators, showing never-before-seen footage from the insurrection, including Capitol security camera video and images from a body camera worn by D.C. Metropolitan Police Department officer.
"He told them to fight like hell, and they brought us hell on that day," Raskin said of Trump's words.
Meanwhile, Trump's lawyers dismissed the impeachment case against the former president as "political theater." In the remarks before the Senate on Friday, van der Veen called Trump's second impeachment an appalling abuse of power and divisive.
He said, "No thinking person could seriously believe that Trump's Jan. 6 speech on the Ellipse could incite an insurrection." This is part of a long-running "witch hunt" that has continued for years, van der Veen told senators.
"The article of impeachment now before the Senate is an unjust and blatantly unconstitutional act of political vengeance," van der Veen said, urging the Senate to reject a conviction.
Trump's lawyers have also claimed that he didn't encourage violence and that his comments at the rally on Jan. 6 are protected by the First Amendment.
Central to the defense has been the question of constitutionality. Trump's team has said Trump cannot be tried as a former president, a claim disputed by many constitutional scholars.
Raskin, a former constitutional law professor, told NPR's Kelsey Snell that the Constitution applies "on your first day of office; it applies on your last day in office and everything in between."
He added: "Everybody can understand that if we had a rule that you can't be tried for anything that you did in your last three or four or five weeks in office that would basically be sending an extremely dangerous signal to future presidents."
Will Trump be convicted?
A Trump conviction is very unlikely. The Democratic caucus would need 17 Republicans to join in voting yes to convict Trump. In Tuesday's vote on the constitutionality of the trial, only six Republicans broke with their GOP colleagues, a vote that likely foreshadows the intentions of most Republican senators in the trial.
However, if the Senate does convict Trump, senators would then vote on whether to bar Trump from seeking any federal office in the future. That vote requires a simple majority.
In a previous version of this story, opening statements made by Trump lawyer Michael van der Veen were mistakenly attributed to Bruce Castor Jr. These statements included characterizing the trial as "political vengeance" that is part of a years-long "witch hunt."