When the first trial stemming from the attack on the Capitol opens Monday, it will set the stage for prosecutors to do more than merely lay out the details of how the defendant, Guy Wesley Reffitt, sought to storm the building with a pistol at his hip.

For the first time in a courtroom, they will present a broad portrait of the violent chaos that erupted that day and seek to persuade a jury that the pro-Trump mob that Reffitt is accused of joining struck at the heart of U.S. democracy by disrupting the transition of presidential power.

The trial, which will take place in U.S. District Court in Washington and begin Monday morning with jury selection, may not be the flashiest or most significant of the dozens of Capitol riot cases that are scheduled to go to trial this year.

But because it is the first to reach a courtroom, it will most likely set the tone for those that follow and serve as a kind of proving ground for the charges prosecutors have filed against hundreds of defendants.

At the heart of Reffitt’s case is the accusation that the defendant, an oil industry worker with purported ties to a Texas militia, obstructed the work of Congress on Jan. 6, 2021, when a joint session of the House and Senate met to certify the results of the 2020 election. Prosecutors say he donned body armor and a helmet mounted with a video camera, and placed himself at “the front of the pack” that charged the Capitol.

The obstruction charge — one of five counts lodged against him — has been used in lieu of other crimes like sedition or insurrection in scores of Capitol riot cases to describe the disruption that occurred when the mob forced lawmakers to flee.

Passed in 2002 as part of the Sarbanes-Oxley Act, which sought to reduce corporate malfeasance, the obstruction provision was initially intended to prohibit activities like shredding documents or tampering with witnesses in congressional inquiries.

Several defense lawyers tried to get the charge dismissed, arguing that prosecutors had stretched it far beyond its scope and were trying to criminalize behavior that resembled ordinary protest protected by the First Amendment.

But 10 federal judges disagreed and allowed the charge to be used.