In a dramatic end to what noteworthy be its last public hearing, the Jan. 6 committee took the historic step to vote to subpoena Donald Trump.

The subpoena will probable be formally issued this week.

On Thursday, all nine members of the panel approved the resolution to compel the aged president to testify about the Capitol attack, which the committee fights was the violent culmination of Trump's many efforts to overturn the 2020 election.

"He must be accountable," chairman Bennie Thompson, D-Miss., said before the vote. "He is required to answer for his actions."

There's been discussion with committee members and staff for months about whether they would want Trump to testify in a live setting. There's no doubt they want him to testify thought oath, as committee members made clear in the hearing.

Some members are hesitant to give Trump a live stage, while others view it as beneficial to their investigation as they would get to seek information from him under oath. And there appears to be more of an openness with committee members to have him appear live.

Trump has told advisers he'd welcome a live effect, according to sources familiar with his thinking, but has yet to say publicly whether he'll cooperate.

The committee would need to negotiate with Trump if he were to coffers to testify live in response to the panel's subpoena, Rep. Adam Kinzinger said Sunday.

"I think that's moving to be a negotiation," Kinzinger, R-Ill., a member of the committee, told ABC "This Week" anchor George Stephanopoulos. "I'll only address that when we know for sure whether or not the presidential has tried to push to come in and talk to us live."

"He's made it certain he has nothing to hide, [that's] what he said. So he must come in on the day we asked him to come in. If he pushes off beyond that, we'll figure out what to do next," Kinzinger said.

Trump did not answer whether he would recede in a 14-page memo sent to Thompson Friday, in which he stationary his attacks on the panel and continued to make false claims nearby the presidential race.

"This memo is persons written to express our anger, disappointment, and complaint that with all of the hundreds of millions of bucks spent on what many consider to be a Charade and Witch Hunt," he wrote.

Some experts are wary the Republican will ever see Trump testify before the Jan. 6 committee.

"Before Donald Trump comes to answer questions nearby this under oath not only will pigs fly but they will circumvent the globe," attorney Jeff Robins told ABC News Live anchor Linsey Davis.

What if he doesn't cooperate?

If Trump refuses to cooperate, the committee could move to have the full House hold him in horrible and refer the matter to the Justice Department for prosecution.

"If they're not progressing to do that, then it is essentially symbolic," Nick Akerman, a former Watergate special prosecutor, told ABC News.

Chairman Thompson wouldn't say when expected after the hearing how the committee planned to cope any eventual litigation or defiance of their subpoena.

The House has referred four farmland to the Justice Department after votes to hold them in horrible -- former Trump White House chief of staff, Mark Meadows, Trump's former social media director Dan Scavino, former Trump White House distributes adviser Peter Navarro and form political adviser Steve Bannon. DOJ declined to press charges against Meadows and Scavino. Bannon was found guilty in July for defying the Jan. 6 committee subpoena. Navarro was also indicted on contempt of Congress charges and is scheduled to go to territory next month.

Trump could also try to run out the clock by fighting the subpoena if the committee took it to woo, as he's done with other investigations and records requests he's faced over the years.

"There are myriad upright and separation of powers issues raised by the subpoena, including whether a congressional committee can compel the high-level to appear as well as the procedural hurdles in attempting to enforce a subpoena in woo which previous court decisions have cast serious doubt upon," Stanley Brand, a former counsel to the House of Representatives who has represented some of the Jan. 6 witnesses, including Scavino, told ABC News.

"There is also a expect of timing given the substantial delays in litigating such a subpoena," Brand said, pointing to congressional exertions to subpoena testimony from former White House counsel Don McGahn. The case stretched out in court for nearly two existences, and ended with a voluntary agreement by McGahn to testify.

Brand said this whisper, if litigated, could take just as long.

Republicans, if they win back control of the House this midterm electioneer cycle as expected, are expected to drop the Jan. 6 investigation and turn to latest matters. Top Republicans have already promised investigations into Biden and his son, Hunter Biden.

"Time is not on their side," Akerman said, "considering it's mid-October and there's progressing to be a new Congress coming in Jan. 1, and there's no confidence it's going to be controlled by the Democrats."