Donald Trump's historic second impeachment trial, which opens Tuesday, will follow rules codified in 1868, but the proceedings will run on a tight schedule agreed by Republicans and Democrats.

After the Capitol riots of January 6, the House of Representatives formally accused Trump of "incitement of insurrection" on January 13, just a week before the defeated president left office.

On January 25, the article of impeachment was delivered by House "managers" to the Senate, the upper chamber.

The next day, 100 senators were sworn in as jurors. They negotiated how the case would unfurl at the same time that Joe Biden's new administration works to secure key appointments and to pass a massive Covid economic package.

The trial will take place every afternoon, and the schedule could continue through the weekend after one of Trump's attorneys withdrew his request that the Senate pause on Saturday for religious reasons.

Tuesday will open on legal debate, with Trump's team arguing he cannot even be tried in the Senate since he has left power.

Democrats will respond that there is precedent, and that the former president must be tried to dissuade future attempts to overturn election results.

Each side will have two hours to present its arguments, and the senators will then vote, by a simple majority, on whether to proceed.

With Democrats narrowly in control of the Senate, the trial is unlikely to end there.

From Wednesday, the prosecution and then the defense will have 16 hours each to present their arguments.

House impeachment managers walk to the Senate on the eve of the trial of former US President Donald Trump
House impeachment managers walk to the Senate on the eve of the trial of former US President Donald Trump AFP / Brendan Smialowski

Democrats prosecutors, led by Jamie Raskin, are expected to show videos of Trump's supporters storming the Capitol -- and Trump's incendiary speech just before the riot.

"You'll never take back our country with weakness," Trump told the crowd outside the nearby White House, urging them to "fight like hell."

In return, his lawyers may present speeches by Democrats allegedly whipping up unrest, and will say Trump's speech is protected by freedom of expression.

Oral arguments will could end Friday, or extend into early next week.

Senators are expected to then have four hours to put questions to both parties.

The two sides will speak again for one hour each if they wish to request or contest summoning of witnesses or additional evidence.

The requests will be decided by simple-majority vote. Both the Democrats and Republicans may wish to move quickly to complete the trial.

The Democrats want to move on and implement Biden's agenda, while the Republicans want to present the trial as a quick and conclusive win.

In the final stage, prosecution will have two hours to deliver its indictment and the defense two hours to respond.

Senators can then retire to deliberate and come to a verdict.

According to the Constitution, it will take a two-thirds majority, or 67 senators, for Trump to be found guilty -- a threshold that is not expected to be met.

If he was nevertheless convicted, senators would still have to vote by a simple majority on wheher to bar him from holding office again.