NEW YORK — Judges expressed skepticism on Tuesday, as lawyers for Donald Trump presented a landmark case that ex-presidents should get immunity from criminal prosecution.

Trump's lawyers claimed his time in office protects him from charges connected to his alleged effort to overturn the 2020 election.

The justice department argued the presidency was not "above the law".

Trump, the frontrunner for the Republican presidential nomination, left the Iowa campaign trail to attend.

The 77-year-old is accused by special counsel Jack Smith of trying to overturn President Joe Biden's election victory in 2020.

The former president maintains that he should not face criminal charges because he was acting as president at the time.

The former president has for years cited presidential immunity in his efforts to thwart civil and criminal cases brought against him.

After the hearing, Trump said his side were "doing very well" in the case and claimed he was facing political persecution from the Biden administration.

The case, which will likely make its way to the US Supreme Court after this court's ruling, could have a profound effect on the future of the American presidency and what is allowable by an individual who holds the office.

It may also delay Trump's criminal trial for weeks, if not months, during a fractious 2024 political campaign in which the former real estate mogul is a leading contender.

As soon as the case began, the three US Court of Appeals for the Washington DC Circuit judges — Karen Henderson, J Michelle Childs and Florence Pan — asked rousing questions about the implications of their decision.

The three judges asked Trump's attorney, Dean John Sauer, whether he would contend that a president could order Navy SEALs — the elite US special forces — to assassinate a political rival, sell presidential pardons and state secrets or — in essence — act without being concerned with criminal prosecution.

Sauer's argument boiled down to the idea that a president who is not convicted for impeachment by Congress cannot be subject to criminal proceedings. Trump, he noted, was impeached but never convicted by the US Senate.

But James Pearce, the government's attorney, said such a precedent could easily be short-circuited and undermine Congress and any potential criminal proceedings.

All a sitting president would have to do is resign before the legislature is able to begin impeachment proceedings to avoid prosecution, he said.

"What kind of world are we living in if... a president orders his SEAL team to assassinate a political rival and resigns, for example, before an impeachment — not a criminal act," he said.

"A president sells a pardon, resigns or is not impeached? Not a crime," Pearce added. "I think that is an extraordinarily frightening future."

More widely, Sauer also contended that prosecuting a president for his actions in office could paralyze government, particularly the executive branch.

He claimed that authorizing "the prosecution of a president for his official acts would open a Pandora's Box from which the nation may never recover".

He posed the hypotheticals that George W Bush could be prosecuted for "giving false information to Congress" to make the case for the invasion of Iraq, and that Barack Obama could face charges "for allegedly authorizing drone strikes targeting US citizens located abroad".

While the judges seemed open to the government's arguments, they also expressed concern about what their decision could lead to and the "Pandora's Box" raised by Trump's attorneys.

Judges Henderson and Childs both said they wanted to issue a ruling that prevented a "tit-for-tat" prosecution. They worried a broad ruling could create an opportunity for individuals to unnecessarily prosecute a future rival in the White House.

How they might narrow their decision is not immediately clear, however.

Jack Smith, the special counsel prosecuting Donald Trump, warned that shielding the former president from prosecution "threatens to license presidents to commit crimes to remain in office".

The decision made by this court — and likely the US Supreme Court — will decide how a major American trial will continue and could have major implications for the office of the presidency.

In legal filings ahead of this hearing, the special counsel prosecuting him, Jack Smith, warned the court that a failure to allow Trump to be prosecuted "threatens to license presidents to commit crimes to remain in office".

The immunity defense was rejected by US District Court Judge Tanya Chutkan in December, who ruled that having served as president does not entitle him to a "lifelong 'get-out-of-jail-free' pass".

In a fundraising email on Wednesday, Trump said President Biden and Smith were "attempting to strip" him of his rights.

A poll by CBS News suggests most Americans believe Trump should not be protected from prosecution for actions he took while president.

The criminal trial in this election fraud case is scheduled for March 4, but is on hold pending the ruling by the appeals court, which has two judges appointed by Democratic presidents and one by a Republican.

Whichever way the judges rule, the case is widely expected to end up in the US Supreme Court, where conservatives hold a 6-3 majority. — BBC