With a smile on her face, Judge Childs noted that Donald Trump's legal team has argued Special Counsel Jack Smith was unlawfully assigned to prosecute him.
She asked Dean John Sauer if he would argue the same.
Sauer does not take the bait, brushing away the question by saying that question is not being raised in this appeal.
Trump lawyer quizzed over possible contradiction
It seems Trump's impeachment proceedings - from which he was acquitted - may be coming back to bite him. It's been coming up quite a bit in this hearing.
Judge Pan reminds Sauer of the argument made during Trump's impeachment that "there would be an option for criminal prosecution later".
So why has team Trump's position now changed, she asks.
Sauer says it's his belief that there was a "distinction between the judicial process and the investigative process".
He argues that no one is immune from judicial process, and that is a fact not inconsistent with presidential immunity, rooted in the separation of powers
Trump lawyer gets animated
Sam Cabral
Reporting from the courthouse
Dean John Sauer formerly served as Missouri's solicitor general, the top lawyer in government litigation, and used to clerk for the late Justice Antonin Scalia, a conservative Supreme Court icon.
In December 2020, the then-solicitor general filed a motion on behalf of his state to have the Supreme Court toss out the vote counts in key states Donald Trump lost to Joe Biden. It was an unsuccessful final gambit to help keep Trump in power.
The bespectacled Sauer has a gravelly voice and an even lawyerly manner.
But he grew notably animated at one point.
Leaning forward toward Judge Childs and pointing back at his client, he asked the panel to consider the broader picture as he sees it - that Trump is being prosecuted by his top political opponent's administration.
The question of impeachment comes up
Judge Childs has suggested that because Trump's lawyer has conceded that presidents can be prosecuted under certain circumstances, they don't have the "absolute immunity" that Trump's legal team claims he has from holding office.
"You're conceding that presidents can be criminally prosecuted, under certain circumstances, doesn't that narrow the issues before us to, can a president be impeached?" she asks Trump's lawyer.
She says if a president is tried and convicted for impeachment that would make the president open to be criminally prosecuted.
"And isn't that also a concession that a president can be criminally prosecuted for an official act?"
Remember - Trump was impeached but he was acquitted.
'So you're saying a president could order rival's assassination and be protected?'
Florence Pan, one of the judges in court today, is putting some hypotheticals to Sauer - Trump's attorney - to test his argument of total immunity of presidents.
Could a president order Navy SEALs to assassinate a political rival, could they sell presidential pardons, sell state secrets, and be protected from criminal prosecution, she asks.
There's some back-and-forth, but she summarises his response as arguing that: if a president is not impeached, they should not be subject to criminal proceedings.
Prosecuting presidents would open Pandora's Box - Trump's lawyer
One of the first exchanges in this hearing covers what impact there might be from allowing Trump to be prosecuted.
Dean John Sauer, one of Trump's lawyers who wants Trump to have immunity, said "to authorise the prosecution of a president for his official acts would open a Pandora's Box from which the nation may never recover".
He asks the three judges: "Could George W Bush be prosecuted for obstruction of an official proceeding for allegedly giving false information to Congress to induce the nation to go to war in Iraq under false pretences?
"Could President Obama be potentially charged with murder for allegedly authorising drone strikes targeting US citizens located abroad?"
Straight into questioning
Sam Cabral
Reporting from the courthouse
The three judges entered the room just after 9:30 local time and they launched right into their questions.
Judge Karen Henderson, appointed by former Republican president George W Bush, is in the middle seat.
Flanking her on left and right are Judge J Michelle Childs and Judge Florence Pan, both appointed to this court in 2022 by President Joe Biden.
As Dean John Sauer, Donald Trump's lawyer, argues his case, Judges Childs and Pan have wasted no time grilling him with questions.
Pan, in particular, appears very sceptical of the appeal.
Childs is listening intently and making several notes, while Henderson has largely sat back as she listens.
Hearing begins
And we're off - stick with us and we'll bring you updates.
You can also listen to the hearing by pressing the play button at the top of the page.
This case will answer a question never before asked in American history
Today's appeal is centring on one question: Whether or not a US president can have total immunity from criminal prosecution for things they did while president.
This is a huge question for the American system, a question that has never really been asked before.
It will also potentially have an impact on Trump's case in Georgia, a state-level case which is over accusations Trump tried to overturn the election there.
If he is granted immunity by this court, that would make that case very difficult to proceed.
How did we get here?
The special counsel has charged Trump with illegally attempting to overturn an election.
Trump, though, says he has immunity from those charges.
In early December the federal judge in the case, Tanya Chutkan, said there was no legal basis for concluding presidents not facing criminal charges once they are no longer in office.
"That position does not confer a lifelong 'get-out-of-jail-free' pass,” she wrote.
While the appeals court is expediting its process, a final decision on the matter could still be weeks away.
BreakingTrump arrives at court - US media
ReutersCopyright: Reuters
The former president has just arrived at the court for the hearing, US media are reporting, which is expected to last around one hour today.
We believe he arrived in a motorcade, pictured above - but we have not seen him ourselves.
Waiting for Trump
Sam Cabral
Reporting from the courthouse
Donald Trump is returning to a federal courtroom in DC.
In August, he was processed in this very building - which sits only a few blocks away from the White House - as a criminal defendant.
Now, he is coming back to watch a hearing that could decide when and whether he will be tried for his alleged efforts to overturn the 2020 election.
Courtroom 31 is a small room on the building's fifth floor with limited seating, but it appears to have nearly filled up with several members of the public and media.
Also waiting inside is Special Counsel Jack Smith, the man prosecuting Donald Trump.
This one was brought by Special Counsel Jack Smith and is possibly the biggest. Whatever is decided here will be appealed by the losing side to the Supreme Court.
Like some of those other cases, it involves Trump’s efforts to overturn the 2020 election.
Trump says he has immunity from charges he broke the law because he was still president and carrying out his duties at the time of 6 January 2021. The special counsel, though, says the immunity given to presidents does not apply here.
Today’s judges will likely not come to unanimous decision
The appeals court is one of the last stops before the Supreme Court, and in many ways it mimics the highest court in the land.
A panel of judges will hear arguments from both sides for roughly an hour this morning and then render a decision in writing later.
And, just as with the Supreme Court, the three judges come from both political parties. Two were appointed by President Joe Biden, a Democrat, in 2022 - Florence Pan and J. Michelle Childs. The third, Karen LeCraft Henderson, was appointed former President George Bush, a Republican, in 1990.
Judge Pan prevailed. In the majority opinion she wrote, she described those who breached the Capitol as “rioters.” Judge Henderson referred to them as “protesters” in a dissenting opinion.
Judge Henderson also took Trump’s side on separate issues such as releasing tax records and congressional subpoenas while he was in office.
Donald Trump expected to be at court
ReutersCopyright: Reuters
The former president posted on social media on Monday morning that he plans to be at the Washington DC courthouse.
In his post, Trump again asserted his claim that he is immune from charges of wrongdoing on 6 January.
"The indictment alleges only official acts, so it must be dismissed."
Trump also says that under the US Constitution only a president who has been impeached can be criminally charged. He is the first current or former president to face criminal charges.
Landmark Trump immunity case about to be heard
It's just coming up to 09:00 in Washington DC, where a landmark legal case will be heard shortly about whether Donald Trump should be immune from criminal prosecution.
The Republican former president's lawyers will argue that the office of the White House shields him from his 2020 election fraud charges. Trump, who says he will attend, is accused by a special counsel of trying to overturn Joe Biden's victory.
The outcome of this hearing could have a huge impact on Mr Trump's future. More on the case here - and stick with us for updates.
Live Reporting
Edited by Francesca Gillett & Lisa Lambert
All times stated are UK
Was Jack Smith unlawfully assigned?
Sam Cabral
Reporting from the courthouse
With a smile on her face, Judge Childs noted that Donald Trump's legal team has argued Special Counsel Jack Smith was unlawfully assigned to prosecute him.
She asked Dean John Sauer if he would argue the same.
Sauer does not take the bait, brushing away the question by saying that question is not being raised in this appeal.
Trump lawyer quizzed over possible contradiction
It seems Trump's impeachment proceedings - from which he was acquitted - may be coming back to bite him. It's been coming up quite a bit in this hearing.
Judge Pan reminds Sauer of the argument made during Trump's impeachment that "there would be an option for criminal prosecution later".
So why has team Trump's position now changed, she asks.
Sauer says it's his belief that there was a "distinction between the judicial process and the investigative process".
He argues that no one is immune from judicial process, and that is a fact not inconsistent with presidential immunity, rooted in the separation of powers
Trump lawyer gets animated
Sam Cabral
Reporting from the courthouse
Dean John Sauer formerly served as Missouri's solicitor general, the top lawyer in government litigation, and used to clerk for the late Justice Antonin Scalia, a conservative Supreme Court icon.
In December 2020, the then-solicitor general filed a motion on behalf of his state to have the Supreme Court toss out the vote counts in key states Donald Trump lost to Joe Biden. It was an unsuccessful final gambit to help keep Trump in power.
The bespectacled Sauer has a gravelly voice and an even lawyerly manner.
But he grew notably animated at one point.
Leaning forward toward Judge Childs and pointing back at his client, he asked the panel to consider the broader picture as he sees it - that Trump is being prosecuted by his top political opponent's administration.
The question of impeachment comes up
Judge Childs has suggested that because Trump's lawyer has conceded that presidents can be prosecuted under certain circumstances, they don't have the "absolute immunity" that Trump's legal team claims he has from holding office.
"You're conceding that presidents can be criminally prosecuted, under certain circumstances, doesn't that narrow the issues before us to, can a president be impeached?" she asks Trump's lawyer.
She says if a president is tried and convicted for impeachment that would make the president open to be criminally prosecuted.
"And isn't that also a concession that a president can be criminally prosecuted for an official act?"
Remember - Trump was impeached but he was acquitted.
'So you're saying a president could order rival's assassination and be protected?'
Florence Pan, one of the judges in court today, is putting some hypotheticals to Sauer - Trump's attorney - to test his argument of total immunity of presidents.
Could a president order Navy SEALs to assassinate a political rival, could they sell presidential pardons, sell state secrets, and be protected from criminal prosecution, she asks.
There's some back-and-forth, but she summarises his response as arguing that: if a president is not impeached, they should not be subject to criminal proceedings.
Prosecuting presidents would open Pandora's Box - Trump's lawyer
One of the first exchanges in this hearing covers what impact there might be from allowing Trump to be prosecuted.
Dean John Sauer, one of Trump's lawyers who wants Trump to have immunity, said "to authorise the prosecution of a president for his official acts would open a Pandora's Box from which the nation may never recover".
He asks the three judges: "Could George W Bush be prosecuted for obstruction of an official proceeding for allegedly giving false information to Congress to induce the nation to go to war in Iraq under false pretences?
"Could President Obama be potentially charged with murder for allegedly authorising drone strikes targeting US citizens located abroad?"
Straight into questioning
Sam Cabral
Reporting from the courthouse
The three judges entered the room just after 9:30 local time and they launched right into their questions.
Judge Karen Henderson, appointed by former Republican president George W Bush, is in the middle seat.
Flanking her on left and right are Judge J Michelle Childs and Judge Florence Pan, both appointed to this court in 2022 by President Joe Biden.
As Dean John Sauer, Donald Trump's lawyer, argues his case, Judges Childs and Pan have wasted no time grilling him with questions.
Pan, in particular, appears very sceptical of the appeal.
Childs is listening intently and making several notes, while Henderson has largely sat back as she listens.
Hearing begins
And we're off - stick with us and we'll bring you updates.
You can also listen to the hearing by pressing the play button at the top of the page.
This case will answer a question never before asked in American history
Gary O'Donoghue
Washington correspondent
Today's appeal is centring on one question: Whether or not a US president can have total immunity from criminal prosecution for things they did while president.
This is a huge question for the American system, a question that has never really been asked before.
It will also potentially have an impact on Trump's case in Georgia, a state-level case which is over accusations Trump tried to overturn the election there.
If he is granted immunity by this court, that would make that case very difficult to proceed.
How did we get here?
The special counsel has charged Trump with illegally attempting to overturn an election.
Trump, though, says he has immunity from those charges.
In early December the federal judge in the case, Tanya Chutkan, said there was no legal basis for concluding presidents not facing criminal charges once they are no longer in office.
"That position does not confer a lifelong 'get-out-of-jail-free' pass,” she wrote.
Trump then appealed her decision. The alleged election fraud case is on pause while that appeal works its way through the legal system.
While the appeals court is expediting its process, a final decision on the matter could still be weeks away.
BreakingTrump arrives at court - US media
The former president has just arrived at the court for the hearing, US media are reporting, which is expected to last around one hour today.
We believe he arrived in a motorcade, pictured above - but we have not seen him ourselves.
Waiting for Trump
Sam Cabral
Reporting from the courthouse
Donald Trump is returning to a federal courtroom in DC.
In August, he was processed in this very building - which sits only a few blocks away from the White House - as a criminal defendant.
Now, he is coming back to watch a hearing that could decide when and whether he will be tried for his alleged efforts to overturn the 2020 election.
Courtroom 31 is a small room on the building's fifth floor with limited seating, but it appears to have nearly filled up with several members of the public and media.
Also waiting inside is Special Counsel Jack Smith, the man prosecuting Donald Trump.
Which case is this?
You'd be forgiven for wondering which of Trump's court cases we're covering today - there are quite a few which you can read about here.
This one was brought by Special Counsel Jack Smith and is possibly the biggest. Whatever is decided here will be appealed by the losing side to the Supreme Court.
Like some of those other cases, it involves Trump’s efforts to overturn the 2020 election.
Trump says he has immunity from charges he broke the law because he was still president and carrying out his duties at the time of 6 January 2021. The special counsel, though, says the immunity given to presidents does not apply here.
Today’s judges will likely not come to unanimous decision
The appeals court is one of the last stops before the Supreme Court, and in many ways it mimics the highest court in the land.
A panel of judges will hear arguments from both sides for roughly an hour this morning and then render a decision in writing later.
And, just as with the Supreme Court, the three judges come from both political parties. Two were appointed by President Joe Biden, a Democrat, in 2022 - Florence Pan and J. Michelle Childs. The third, Karen LeCraft Henderson, was appointed former President George Bush, a Republican, in 1990.
Judges Pan and Henderson have already disagreed in a key 6 January-related case, which was decided in October.
Judge Pan prevailed. In the majority opinion she wrote, she described those who breached the Capitol as “rioters.” Judge Henderson referred to them as “protesters” in a dissenting opinion.
Judge Henderson also took Trump’s side on separate issues such as releasing tax records and congressional subpoenas while he was in office.
Donald Trump expected to be at court
The former president posted on social media on Monday morning that he plans to be at the Washington DC courthouse.
In his post, Trump again asserted his claim that he is immune from charges of wrongdoing on 6 January.
“President Trump has absolute immunity from prosecution for his official acts as president,” his lawyers wrote in a recent court filing.
"The indictment alleges only official acts, so it must be dismissed."
Trump also says that under the US Constitution only a president who has been impeached can be criminally charged. He is the first current or former president to face criminal charges.
Landmark Trump immunity case about to be heard
It's just coming up to 09:00 in Washington DC, where a landmark legal case will be heard shortly about whether Donald Trump should be immune from criminal prosecution.
The Republican former president's lawyers will argue that the office of the White House shields him from his 2020 election fraud charges. Trump, who says he will attend, is accused by a special counsel of trying to overturn Joe Biden's victory.
The outcome of this hearing could have a huge impact on Mr Trump's future. More on the case here - and stick with us for updates.