Ahead of the hearing, Chairman Bennie Thompson, D-Miss., left the door open to subpoenas for the former president and those close to him on Jan. 6.

"Wherever the investigation leads us," Thompson told ABC News Correspondent Kyra Phillips, when asked also about subpoenas for the House GOP leader and Ivanka Trump. "We will look at who made phone calls to the White House that day, we'll look at whether or not there were any text messages, where there any emails -- all of that is part of the investigation."

Thompson said the August recess for the committee will include a lot of work and include conversations with Attorney General Merrick Garland and the White House.

"We are looking for a cooperative investigation, so whatever it takes to get that cooperation we plan to do," he said.

Rep. Adam Schiff, D-Calif., a member of the panel and chairman of the House Intelligence Committee, who briefed reporters on a call ahead of the hearing, said it was important to have the officers explain the brutality of what they confronted, with the help of video footage from that day.

Schiff said the officers can "put to rest some of the revisionist history, the effort to whitewash what took place and understand keenly the importance of getting to the truth about what led up to that insurrection and what happened thereafter."

He added, "We didn't want to compel anyone to testify that didn't want to or didn't feel that they could. A lot of those who were the most severely injured continue to struggle with the after-effects of that day, so we want to be sensitive to those concerns."

Metropolitan Police officer Michael Fanone, who was seen on video getting brutally attacked by rioters, told ABC News Congressional Correspondent Rachel Scott he plans to testify in uniform and won't let politics surrounding the committee hinder the truth in his testimony.

At Tuesday’s hearing, titled “The Law Enforcement Experience on January 6th,” the panel will hear from police officers who protected lawmakers from rioters during the assault on the Capitol and have them explain new video footage showing what they experienced that day.

Harrowing testimonies are expected from Capitol Police officers Harry Dunn and Aquilino Gonell and Michael Fanone and Daniel Hodges of the Metropolitan Police Department.

Chairman Bennie Thompson, D-Miss., and Rep. Liz Cheney, R-Wyo., will each deliver opening statements ahead of testimony from the officers. The opening statements from police officers will each be roughly five minutes, though the committee won't be enforcing the "5-minute rule" on members and witnesses as it typically does in major hearings. There will only be one round of questions.

The hearing is expected to go two to three hours and will feature new video elements from the attack, according to a congressional aide.

House Republican Leader Kevin McCarthy, joined by other Republican leaders and the five GOP members he appointed to the committee, held a news conference at the Capitol about an hour before the first hearing was set to began to air grievances about Reps. Jim Banks and Jim Jordan being rejected by House Speaker Nancy Pelosi.

The group attempted to place blame for Jan. 6 on Pelosi.

"The American people deserve to know the truth that Nancy Pelosi bears responsibility as speaker of the House for the tragedy that occurred on Jan. 6," said Rep. Elise Stefanik, who replaced Cheney in her No. 3 GOP leadership role earlier this year.

One reporter noted that Pelosi didn’t say the election was stolen or call her supporters to the Capitol, asking McCarthy, "So are you trying to cover up what the former president's role was on Jan. 6?"

"Nothing, we're not pre-determining any questions. We'd like to be on the committee to ask them,” he replied, before resuming his attacks on Pelosi and the Democratic-led committee.