Caleb Berry, center, wearing a backward baseball cap, walks with other members of the Oath Keepers on the steps of the U.S. Capitol on Jan. 6, 2021. (Jim Bourg/Reuters)

Caleb Berry got little sleep on the night of Jan. 6, 2021. The 19-year-old said he lay awake in bed at a Hilton Garden Inn, not far from where he and other members of the far-right Oath Keepers group had just stormed the U.S. Capitol, regretting what he had done.

Two years later, Berry, 21, testified in federal court in D.C. against four fellow members of the Oath Keepers facing charges of seditious conspiracy — the second such group to go on trial. Going further than other cooperators, Berry testified this week that the extremists hatched an explicit plan to enter the Capitol and stop the certification of Joe Biden’s presidential victory — which could be a boon to prosecutors case.

But he also acknowledged he was not always truthful with investigators, as defense attorneys highlighted inconsistencies in his testimony. Those on trial have argued that there was no plan or conspiracy, only a spontaneous decision to follow the crowd into the building, and that an armed “Quick Reaction Force” stationed in Virginia was just an elderly asthmatic who spent hours on Jan. 6 searching for his car.

Berry said that he joined the Oath Keepers group from Tampa in November 2020, pledging that he “was ready to die” to “defend the Constitution.”

But after the attack at the Capitol on Jan. 6, which left scores of officers wounded and five people dead in the aftermath, Berry said he “knew that I had made a huge mistake.”

Instead of a patriotic victory, he testified, “it was a traumatizing event.”

Berry said he was persuaded to join the trip that put the Oath Keepers in D.C. on Jan. 6 by Kelly Meggs, the head of the Florida Oath Keepers. After a trial last year, Meggs and Oath Keepers founder Stewart Rhodes were convicted of seditious conspiracy in November; associates, including another Florida Oath Keeper named Kenneth Harrelson, were acquitted of that charge but found guilty of other felonies related to the riot.

Now four more are on trial, accused of opposing the U.S. government by force: Joseph B. Hackett, 52; Roberto Minuta, 37; David Moerschel, 44; and Edward Vallejo, 64.

Berry, a line cook, testified he had joined the far-right group weeks earlier because he was “sick of hiding my opinions,” particularly from his girlfriend. She opposed Trump and the Oath Keepers and had already persuaded him not to join the military, he said. In a message, Meggs called Berry “a bada--.”

Berry testified that he and Meggs drove with other members from Florida to D.C., stashing weapons at a hotel in Ballston, Va. They provided protection for speakers at President Donald Trump’s speech and their families, then followed those “VIPs” to the Capitol, he said.

On the way, they learned the Capitol had been breached. On the east side of the building, Berry testified, Meggs led a huddle of Oath Keepers and told them that the election had been “illegitimate and unconstitutional” and that “we were going to try to stop the vote count.” They then organized into a military-style “stack,” he said, and headed up the stairs into the building “like a battering ram.”

Other rioters followed the Oath Keepers’ lead because “we had armor, we had military members, we were experienced,” Berry testified.

In the earlier trial, prosecutors highlighted a three-minute phone call between Meggs and Rhodes just before the stack ascended the stairs. Rhodes denied issuing any order to Meggs, saying he couldn’t hear him on the call.

Berry described friction between Rhodes and Meggs — a dynamic that Oath Keepers attorney Kellye SoRelle also relayed to the House committee investigating the Jan. 6 attack. SoRelle, now accused of conspiracy and other charges, told lawmakers in April that the Florida Oath Keepers “went rogue” by working with the Proud Boys. Berry testified that the feeling was mutual; Meggs told him that “Stewart Rhodes was in it for himself” and that Florida Oath Keepers should “stick to ourselves.”

Berry did not testify against Rhodes, Meggs or Harrelson at the previous trial, although a prosecutor said in court Wednesday that Berry went through two rounds of preparation to do so. The Justice Department has a roster of more than a dozen cooperating Oath Keepers to pull from, allowing them to put witnesses on the stand who have not yet been subject to cross-examination.

The two cooperators who did testify at the earlier trial said there was no explicit plan to enter the Capitol, only an unspoken agreement that doing so would further the group’s goal of keeping Trump in office.

Berry was key to implicating Hackett, who prosecutors say organized Sarasota, Fla., members and brought weapons to D.C. Berry testified that he and Hackett dropped long-gun cases and ammunition off in Ballston on Jan. 5 for the “Quick Reaction Force” and that Hackett was in the huddle with Meggs before they entered the Capitol. Berry also said that he and Hackett discussed deleting evidence on the way back to Florida.

But under cross-examination by Hackett’s attorney, Angie Halim, Berry admitted past dishonesty and ongoing confusion about what happened on Jan. 6.

Berry had described the Oath Keepers as breaking open the East Rotunda doors from the outside, pushing them in; the doors actually open outward, from the inside. Before his first meeting with the FBI, Berry had written an 11-page account of Jan. 6 that did not include Meggs’s directive about stopping the vote count, and in earlier interviews with investigators he said he couldn’t remember who voiced it. He had also told the FBI he decided alone to wipe his phone and did so secretly.

“I was trying to downplay and minimize,” Berry testified.

He claimed he was immediately ashamed of his participation in the Capitol attack. But in a message to other Florida Oath Keepers on Jan. 11, Berry struck a defiant tone.

“For those of us still interested in continuing, this fight is not over,” he wrote. “We must be aggressively free or we won’t be free at all.” Berry claimed that message was about forming a new group, separate from the Oath Keepers.

He said he was still with his “liberal” girlfriend.

“Has she said, ‘I told you so?’” asked Scott Weinberg, Moerschel’s attorney.

Berry, who faces a guideline sentence of roughly five years in prison, smiled.

“Plenty of times,” he said.

Spencer S. Hsu contributed to this report.

The Jan. 6 insurrection

The report: The Jan. 6 committee released its final report, marking the culmination of an 18-month investigation into the violent insurrection. Read The Post’s analysis about the committee’s new findings and conclusions.

The final hearing: The House committee investigating the attack on the U.S. Capitol held its final public meeting where members referred four criminal charges against former president Donald Trump and others to the Justice Department. Here’s what the criminal referrals mean.

The riot: On Jan. 6, 2021, a pro-Trump mob stormed the U.S. Capitol in an attempt to stop the certification of the 2020 election results. Five people died on that day or in the immediate aftermath, and 140 police officers were assaulted.

Inside the siege: During the rampage, rioters came perilously close to penetrating the inner sanctums of the building while lawmakers were still there, including former vice president Mike Pence. The Washington Post examined text messages, photos and videos to create a video timeline of what happened on Jan. 6. Here’s what we know about what Trump did on Jan. 6.