The same senators who fled for their lives during a violent mob attack on their workplace will now decide whether President Donald Trump should be held responsible for inciting that insurrection.

Senators will listen to arguments and debate the second impeachment of Trump in the same chamber from which most of them evacuated Jan. 6 as Capitol Police were overrun by the Trump-inspired invaders. Some of the mob entered that Senate chamber and rifled through their desks and their paperwork.

An officer shot and killed one invader near the House chamber. Other intruders died of medical conditions amid the chaos. Another officer’s quick thinking is credited with misdirecting the first members of the mob away from the Senate when the doors to the chamber were still unsecured, buying crucial time for lawmakers to hide and barricade rooms.

Only in an impeachment trial could victims of such a crime sit in judgment of someone accused of being involved with it, and do so at the scene of the crime. In regular trials in courtrooms across the country, the experience would be thought to wipe away any chance of impartiality.

“What everyone knows is that there are some things you just can’t set aside. It’s in there, it’s in your head,” said Art Patterson, a social psychologist and an expert jury consultant with DecisionQuest. “The more significant it is, the more salient it is, the harder it is to get around.”

But the Senate is not a courtroom. Senators are not simply jurors. The ultimate question about Trump’s behavior is about politics and the Constitution, not guilt beyond a reasonable doubt.

And some legal and congressional experts say the experience of the Jan. 6 attack that disrupted a critical part of the presidential election process means that senators, who witnessed the events and know deeply what’s at stake for the country, actually gives them a better ability to judge a president’s actions.

Trump falsely claimed for weeks that the election was stolen and amplified that claim at a Jan. 6 rally on the National Mall, telling supporters there that if they “don’t fight like hell you won’t have a country anymore.”

Trump told them to march to the U.S. Capitol, where the joint session of Congress was poised to count electoral votes and finalize Trump’s loss.

The House voted 232-197 to impeach Trump the following week on a charge of incitement of insurrection and sought to have him removed from office and disqualified from holding office again.

Tuesday was the first return to the building for senators since since they resumed their session hours after the attack and then went on recess. The timing of a Senate trial has not been settled, but Senate Majority Leader Mitch McConnell said one would not begin until after Trump leaves office.

Josh Chafetz, a professor at Georgetown University Law Center who wrote a book about legislative authority and separation of powers, said senators would be disqualified as jurors in a criminal trial because they had to flee for their lives and “they’re not going to be forgiving of the person who caused that.”

“But that’s not what impeachment is about,” Chafetz said. Instead, this was an attack on a coordinate branch of government, and on the foundations of our constitutional order.

“That actually makes them the most qualified, I think, to determine whether or not he should be removed and disqualified” from holding office again, Chafetz said.

Frank O. Bowman III, a law professor at the University of Missouri and author of “High Crimes & Misdemeanors: A History of Impeachment for the Age of Trump,” said the nation’s framers opted for impeachment as a political process with political actors, over a judicial proceeding that seeks uninvolved jurors to promote neutrality.

“That’s just not possible in an impeachment,” Bowman said, since legislators will often be witnesses to or participants in events related to an impeachment. “And it has never been thought necessary.”

President Andrew Johnson was impeached, in large part, for violating the Tenure of Office Act, and more generally for consistently defying congressional efforts at managing post-Civil War reconstruction, Bowman told CQ Roll Call.

“The senators were, inescapably, interested parties,” Bowman wrote in an email. “That did not disqualify them from sitting in judgment on Johnson.”

It might be called a trial, and the chief justice of the United States might preside, but the rules of courtrooms aren’t in play. There are no standards of proof, no rules of evidence, like those that have been hashed out in the judiciary over the centuries.

Senators are not considered jurors, said Ross Garber, who teaches political investigations and impeachment at Tulane Law School. He pointed to an exchange during President Bill Clinton’s impeachment trial.

At one point, then-Sen. Tom Harkin, D-Iowa, made a motion that House impeachment managers who were presenting their case against Clinton should not refer to the senators as “jurors.” Chief Justice William Rehnquist, as the presiding officer, decided “that the Senate is not simply a jury; it is a court in this case,” and there were no objections.

The Senate makes its own rules that allow for the involvement of senators in ways that wouldn’t be allowed in criminal trials. Garber said Rule XVIII of the Senate’s impeachment rules “specifically contemplates that senators may also be witnesses and provides that they may provide testimony from their normal place in the Senate chamber.”

Reliving trauma

Still, there are signs that the experience left an indelible mark on some senators that will color their view of the impeachment proceedings.

Patterson, the social psychologist, said it would be easy to conclude that lawmakers have the classic symptoms of post-traumatic stress disorder, a mental health condition triggered by a terrifying event, based on the language and looks on their faces in statements after the attack.

And he said that events such as that will affect different people in different ways. In the hours after the attack, senators in floor speeches indicated that it had already changed their thinking and actions.

Utah Republican Sen. Mitt Romney mentioned on the Senate floor that he has 25 grandchildren, “many of them watching TV, thinking about this building, and whether their grandpa was OK. I knew I was OK.”

Virginia Democratic Sen. Mark Warner started his comments with: “I think, like most of us, I am still pretty reeling from what happened today.”

Illinois Democratic Sen. Tammy Duckworth, who lost both of her legs and partial use of her right arm when a rocket-propelled grenade struck the helicopter Duckworth was co-piloting in Iraq, told Fortune magazine that the mob tried to gain entry to her hiding place through a window to the outside.

“That window was shattered. Thank goodness it held so that they never breached my hideaway,” Duckworth said. “Had I been in there I would have been in real jeopardy. It’s pretty badly cracked, and the inside of my hideaway is filled with shattered glass.”

On Tuesday, McConnell said the Senate stood together on the night of Jan. 6 to show the mob it did not have veto power over the rule of law.

“The last time the Senate convened, we had just reclaimed the Capitol from violent criminals who tried to stop Congress from doing our duty. The mob was fed lies. They were provoked by the president and other powerful people,” McConnell said.

McConnell has not said whether he will vote to convict Trump.