Six months after a mob of Donald Trump's supporters stormed the seat of American democracy in the worst attack on the legislature since the war of 1812, the American public will hear the first testimony on the Capitol Riots before a congressional panel on Tuesday.

Lawmakers will receive first-hand accounts from police officers who were attacked by rioters who fought their way into the building, prowled the hallways hunting for the likes of House Speaker Nancy Pelosi, and sought to block certification of Joe Biden's election victory on January 6.

Tuesday's hearing will feature police officers who were physically and verbally abused while defending the Capitol from rioters.

 But the House Republican leadership has essentially boycotted the select committee, pulling its five appointments last week after Pelosi rejected two of Minority Leader Kevin McCarthy's picks.

Instead of leaving the panel with just Democrats, Pelosi has named two Republicans to it. These are Liz Cheney and Adam Kinzinger.

Both Cheney and Kinzinger are forceful Trump critics who had voted for his impeachment in January after the riot, and both have drawn censure from their party for refusing to back Trump's baseless claims that the election was stolen.

Pelosi and others had wanted a bipartisan, independent 9/11-style commission to investigate the riot and its origins. Even McCarthy in January had voiced support.

But with anxiety growing among Republicans concerned that a probe could prove politically damaging for their party ahead of the 2022 midterm elections, and with Trump himself expressing zero interest in relitigating the riot, the party began coalescing against a deep dive on the events of January 6.

Senate Republicans in May blocked the commission, arguing that multiple investigations have already reached conclusions about the riot, and that hundreds of arrests have yielded considerable data about what happened.

"Never in the history of America has a speaker picked the other side, so they are predetermining what comes out" from the probe, McCarthy said on Monday.

He also derided Cheney and Kinzinger as "Pelosi Republicans," and said the two Republican nominees she rejected -- congressmen Jim Banks and Jim Jordan -- "have the right" to sit on the panel.

The speaker had said she welcomed McCarthy's three other appointments, only to have him pull all his nominations when she rejected Banks and Jordan, a Trump stalwart and conservative firebrand.

But she now insists the committee will forge ahead -- with or without more Republican engagement.

"We have to, again, ignore the antics of those who do not want to find the truth," she told ABC on Sunday.

"We will find the truth. That truth will have the confidence of the American people because it will be done patriotically and not in a partisan way."

Five people died during or shortly after the insurrection, while dozens of police were injured.