The January 6 House select committee is expected to make the case at its hearing on Thursday that Donald Trump potentially violated the law when he refused entreaties to take action to stop the 2021 attack on the US Capitol by a mass of his supporters, according to two sources familiar with the matter.

The panel will demonstrate that the former Republican president was “derelict in his duty” to protect the US Congress and might have also broken the federal law that prohibits obstructing an official proceeding before Congress, which had gathered to certify Democrat Joe Biden’s victory in the 2020 presidential election.

Trump could have called on national guard troops to restore order when he saw on TV the melee unfolding at the Capitol, the panel is expected to argue, or he could have called off the rioters via a live broadcast from the White House press briefing room, but he did not. Or he could have sent a tweet trying to stop the violence far earlier than he actually did, during the 187-minute duration of the Capitol attack.

The former president instead only reluctantly posted a tweet in the afternoon of January 6, hours after his top advisors at the White House and Republicans allies in Congress repeatedly implored him to intervene, the select committee will show.

And the panel is expected to reinforce that Trump’s inaction directly contributed to the extended battle between the US Capitol police and rioters, who outnumbered them, since many rioters dispersed after he tweeted the now-infamous video asking them to leave the Capitol.

The sources described what the select committee sees as potential legal culpability for the former president, speaking on the condition of anonymity ahead of the prime time hearing.

Among the witnesses for the eighth hearing – characterized by the panel’s members as a “season finale” with more hearings after the summer recess – include Trump’s former deputy national security advisor Matthew Pottinger and former Trump press aide Sarah Matthews.

The two witnesses with inside knowledge of how the West Wing operated on January 6 are expected to narrate how that day unfolded, starting with how desperately Trump did not want to return to the White House after delivering his speech at the rally at the nearby Ellipse, where he had urged supporters to “fight like hell” to overturn his election defeat.

Former Trump aide Cassidy Hutchinson testified in a previous hearing that Trump was so determined to go to the Capitol alongside his supporters that at one point, infuriated, he attempted to wrestle control of the steering wheel from the Secret Service in the presidential vehicle as they insisted he return to the White House.

The Guardian has learned, according to a person directly familiar with the matter, that in a previously unreported incident, the fracas about going to the Capitol, after Trump told his supporters at the rally to go to Congress and “I’ll be there with you”, continued when he arrived back at the White House, and the argument spilled into the West Wing driveway.

Pottinger and Matthews are expected to testify about what happened when Trump was back at the White House, including details on Trump in his dining room off the Oval Office, where he watched the Capitol attack erupt on TV, transfixed by the images as rioters overran police and rampaged through the halls of Congress, the sources said.

The select committee will show through videotaped testimony from the Trump White House counsel, Pat Cipollone, and other aides, that the former president ignored repeated entreaties from advisers to help stop the Capitol attack, the sources said.

Hutchinson previously testified that she tried to get Trump’s White House chief of staff, Mark Meadows, to lobby Trump – only for him to tell her that the former president “wanted to be left alone”.

The select committee will also show that Trump never once called the national guard or other law enforcement, the sources said.

With Trump unwilling to act, the panel is expected to describe how the duties of commander in chief were effectively assumed by then vice-president Mike Pence, who was sheltering in a loading-dock on the Senate-side of the Capitol after lawmakers had to flee the chamber amid the violence.

“Trump gave no order to deploy the national guard that day, and made no effort to work with the Department of Justice to coordinate and deploy law enforcement assets,” the panel’s vice-chair, Liz Cheney, previously said. “But Mike Pence did each of those things.”

The Guardian has also learned, according to another person directly familiar with the matter, that then First Lady, Melania Trump, appeared to choose not to intervene with her husband or try and stop the Capitol attack herself.

That day, the person said, Melania Trump was conducting a photoshoot for a new rug for the White House residence and when her then chief of staff, Stephanie Grisham, asked if she wanted to tweet condemning the attack, Melania responded curtly: “No.”

Meanwhile, Cipollone told top aides that Trump might have legal liability, the sources said. And the hearing may present more details of the calls that mounted after the insurrection for Pence to convene the Cabinet and remove Trump from office through the 25th Amendment.