She did not name names, but put on the committee's giant screens two electronic messages sent to witnesses.
Former Trump chief of staff Mick Mulvaney predicted the testimony would be damaging for Trump.
"Cheney's closing is stunning: they think they have evidence of witness tampering and obstruction of justice. There is an old maxim: it's never the crime, it's always the coverup," he wrote. "Things went very badly for the former President today. My guess is that it will get worse from here."
Legal experts also immediately offered their analysis of the messages.
Former Deputy Assistant Attorney General Harry Litman wrote, "assuming that's Trump it is a layup of an obstruction felony count."
"Mob bosses send messages to witnesses that say things like they know they're testifying soon, they should stay on the team, the boss reads the transcripts. [Committee] witnesses testified they received that type of message," wrote former U.S. Attorney Joyce Vance.
"This is the most astonishing testimony I have ever seen or heard or read. You could litigate or investigate for a thousand years and never see anything as mind-blowing as this," wrote conservative attorney George Conway.
"Pretty safe bet there will be referrals to DOJ for witness tampering based on that last revelation from Cheney. Remarkably stupid behavior," said former Department of Justice spokesperson Matt Miller.
"How do you square 'things got out of hand' and Trump 'didn't track all the details' with 'he reads transcripts'?" wondered MSNBC chief legal correspondent Ari Melber.
"Prosecutors know what constitutes witness tampering and obstruction of justice. In cities across this country they prosecute alleged gang leaders & conspirators for sending messages like this. To ignore this shreds the rule of law," wrote civil rights attorney Sherrilyn Ifill.
Ambassador Norm Eisen, who served as co-counsel for the House Judiciary Committee in Trump's first indictment, noted the former president could be sentenced to 20 years in federal prison.
"Make no mistake, those texts we just saw will certainly lead to criminal investigation & perhaps prosecution under 18 USC 1512, which punishes witness intimidation with fines, imprisonment for not more than 20 years, or both," he wrote.
Yevgency Vindman, who was an Army Judge Advocate and was retaliated by the Trump administration declared it was, "Brazen witness intimidation and obstruction of congress by Trump world."
Law Prof. Jen Taub said witness intimidation is Trump's modus operandi.
White House counsel Pat Cipollone reportedly worried they would all be charged with obstruction of justice, along with "every crime imaginable."
