Mueller's appearance before two House panels promised to be the TV event of the year in the US House, where politicians will questioned him for more than five hours about the book-length report he released in April.
Democrats hoped that by putting Mueller on television and highlighting the parts of the report that they believe describe Trump's most egregious behaviour, they would be able to ignite new outrage and renew public interest in their investigations into the president.
But Republicans were there too, and defended Trump, who has condemned the probe as a "witch-hunt."
Mueller first appeared before the House Judiciary Committee for three and a half hours. He then appeared before the House Intelligence Committee for about two hours.
Here how it played out, starting with the most recent update on July 24:
House Intelligence Committee concludes hearing
The House Intelligence panel concluded its hearing with Mueller, ending a day of testimony from the former special counsel on his investigation into Russian interference and possible obstruction of justice by Trump.
Mueller says why he didn't subpoena Trump
Mueller told Congress his team decided not to exercise its subpoena powers against Trump because it wanted to expedite the end of the investigation and a subpoena could have led to a lengthy legal fight.
"If we did subpoena the president, he would fight the subpoena and we would be in the midst of the investigation for a substantial period of time," Mueller said. He indicated his office believed it had the authority to subpoena Trump but opted not to do so.
Mueller says he 'generally' agrees Trump wasn't always truthful in answers
Mueller said he "generally" agreed with a characterisation that Trump's written answers to investigators probing Russian interference in the US election were not always truthful.
"Isn't it fair to say that the president's written answers were not only inadequate and incomplete because he didn't answer many of your questions, but where he did, his answers showed that he wasn't always being truthful?" Democrat Val Demings asked as Mueller testified before the House intelligence panel.
"Generally," Mueller said.
Mueller quiet on whether he subpoenaed Trump Jr.
Mueller refused to say whether his team subpoenaed Donald Trump Jr.
Eric Swalwell, a Democrat, asked Mueller if he subpoenaed the president's eldest son or if he wanted to interview him. Mueller responded: "I'm not going to discuss that."
Mueller's report on the Russia investigation, which was released in April, said Trump Jr had "declined to be voluntarily interviewed" by the special counsel's office.
There are two lines in the report, following that statement, that are redacted because they contain grand jury information.
Trump Jr was a key figure in a 2016 campaign meeting with a Russian lawyer in Trump Tower in New York that captured Mueller's attention.
Mueller raises alarm on continued Russian interference
As the House Intelligence Hearing resumed, Mueller raised raises alarm on continued Russian election interference, telling tells Congress, "They're doing it as we sit here."
House Intelligence Committee on short break
The House Intelligence Committee is on a short break. That hearing will continue soon.
Mueller on Trump praise of WikiLeaks: 'Problematic is an understatement'
When asked about Trump's praise of WikiLeaks during the 2016 presidential campaign, Mueller said calling it "problematic is an understatement".
Mueller clarifies answer on indicting Trump
Mueller has clarified that he did not consider bringing criminal charges against Trump as part of his Russia investigation.
Mueller in his congressional testimony Wednesday morning seemed to agree that he did not charge Trump with obstruction of justice because of Justice Department guidance saying a sitting president can't be indicted.
Democrats seized on that answer, but when testimony resumed in the afternoon, Mueller clarified. He said "that is not the correct way to say it".
Mueller said his team "did not reach a determination as to whether the president committed a crime".
Mueller says Trump-Russia probe not a 'witch-hunt'
Mueller said his investigation into Russian interference in the 2016 election was "not a witch hunt".
Trump has repeatedly referred to the Russia investigation as a witch-hunt, including on Wednesday morning when he tweeted the hearings were part of the "Greatest Witch Hunt in U.S. history."
Mueller was responding to a question from intelligence committee Chairman Adam Schiff, a California Democrat.
Top Republican: Hearing is 'political theatre'
The top Republican on the House intelligence committee said a hearing with Mueller is "political theater" and a "Hail Mary" attempt by Democrats to convince Americans that Trump conspired with Russia to win election.
Devin Nunes said there were "red flags" as the Justice Department started investigating Russian contacts with Trump's campaign in 2016. Republicans have argued that the department conspired against Trump as that probe began.
Mueller, who later took over the investigation, said in his report released in April that there was no evidence that Trump's campaign conspired with Russia. But it detailed many contacts between the two.
Nunes called the Mueller hearing the "last gasp of the Russia collusion conspiracy."
House intelligence hearing begins
The House intelligence committee chairman said the Mueller report was "methodical and devastating."
Adam Schiff's prepared remarks come at the start intelligence panel's hearing.
Schiff, a Democrat, said the report also tells the story of "disloyalty to country, about greed and about lies".
Schiff said what is at stake is "our next election, and the one after that, for generations to come."
White House calls hearing an 'embarrasment'
The White House called Mueller's congressional testimony "an epic embarrassment for the Democrats".
Press Secretary Stephanie Grisham issued a statement as Mueller prepared for a second round of testimony on Capitol Hill about his investigation into Russian election interference and obstruction of justice by Trump.
"The last three hours have been an epic embarrassment for the Democrats. Expect more of the same in the second half," Grisham's statement said.
House Judiciary hearing takeaways
As expected, the first of back-to-back congressional hearings ended without major surprises.
In his testimony before the House Judiciary Committee, Mueller stuck with what his office outlined in its 448-page report, which was released in redacted form earlier this year. That report concluded there was no conspiracy between the Trump campaign and Russia. But Mueller declined to make a judgment on whether Trump obstructed justice, though the report outlined 10 instances in which Trump tried to impede the investigation.
Mueller made clear that he did not exonerate Trump and that the president could still be charged when he leaves the office.
The former special counsel also defended his team and the investigation, despite repeated attempts by Republicans to challenge the probe and, at times, Mueller himself.
Democrats chose to highlight the 10 instances the report cited in which Trump might have obstructed justice.
The hearing focused little on Russian interference, which Mueller in his opening statement, said was "among most serious" challenges to American democracy.
House Judiciary Committee hearing ends
The House Judiciary hearing has ended. It lasted three and a half hours and included questioning by all members on the committee.
According to CBS News, there were 110 one-word answers by Mueller.
The House Intelligence hearing will be held after a short break.
Mueller says he didn't seek FBI top job under Trump
Mueller again disputed assertions that he had interviewed with President Trump in 2017 to serve as the FBI director a day before he was appointed to oversee the Russia investigation.
"My understanding of it was (I was) not applying for the job, I was asked to give my input on what it would take to do the job," Mueller told the US House Judiciary Committee. "I interviewed with the president ... it was about the job, but not about me applying for the job."
Trump tweeted on Wednesday that there are "numerous witnesses", including Vice President Mike Pence, who could say that Mueller applied and was interviewed for the job and was "turned down" for it.
Mueller defends report against Republican attacks
Mueller pushed back against Republican attacks with a forceful defence of his report on the Trump-Russia investigation.
Mueller said he doesn't think the politicians have reviewed "a report that is a thorough, as fair, as consistent as the report that we have in front of us".
Trump renews attacks on Mueller probe
With a barrage of morning tweets, Trump renewed his efforts to undermine the credibility of Mueller.
Before Mueller even took his seat to testify, the president tweeted nine times about Mueller and his investigation.
And by mid-morning, Trump and his allies were already spinning the moment as a victory for the White House.
The president, in a pair of tweets, quoted Fox News coverage of the hearing, including anchor Chris Wallace, saying, "This has been a disaster for the Democrats and a disaster for the reputation of Robert Mueller."
Mueller says Trump can be charged when term ends
Mueller affirmed that a president can be charged with crimes after leaving the office.
He said the Department of Justice (DOJ) guidelines prevented him from considering charges against Trump while he is in office.
Because of the longtime DOJ guidance that a sitting president cannot be indicted, Mueller said, "One of the tools a prosecutor would use is not there."
Trump sons go after Democrats on Mueller hearing
President Trump's sons and advisers are weighing in on Mueller's congressional testimony with quips on Twitter targeting Democrats.
Donald Trump Jr called the hearing a "disaster" for Democrats. He said Mueller claims he could not understand the Republicans' questions, but totally gets the ones from Democrats.
Eric Trump says Republican Jim Jordan's comments at the hearing were "spot on". Jordan said Democrats should be investigating what he says are "false accusations" that started the Russia probe.
Former White House press secretary Sarah Sanders said the hearing shows the Russia probe was run by Democrats wanting to destroy Trump.
Trump adviser Kellyanne Conway tweeted three words: "drop the mic."
Highlights so far
In case you need to catch up, here are some highlights after more than two hours of Mueller's testimony before the House Judiciary panel hearing:
On Trump:
- "Obstruction of justice strikes at the core of the government's effort to find the truth and to hold wrongdoers accountable," Mueller said.
- "Based on Justice Department policy and principles of fairness, we decided we would not make a determination as to whether the president committed a crime. That was our decision then and remains our decision today," the former special counsel told the panel.
- Asked whether the report exonerated Trump on the question of obstruction of justice, Mueller said: "That is not what the report said."
- "The president was not exculpated for the acts that he allegedly committed," Mueller told members of Congress.
- Asked if Trump wanted Mueller fired for investigating possible obstruction of justice: "That's what it says in the report, yes. I stand by the report."
On Attorney General William Barr's role:
- "I will not comment on the actions of the attorney general or of Congress," Mueller said.
- "Based on Justice Department policy and principles of fairness, we decided we would not make a determination as to whether the president committed a crime. That was our decision then and remains our decision today," the former special counsel said.
Nature of the probe
- Mueller disagreed with Republican Representative Ken Buck's assertion that said the list of incidents that could be obstruction of justice in the report was an attempt to throw "a bunch of stuff against the wall to see what would stick".
Hearing resumes
After a short break, the House Judiciary panel resumed its hearing with Mueller.
Mueller disputes Trump claim he wanted FBI job
Mueller disputed Trump's claim that Mueller was rebuffed in a bid to fill the post of FBI director.
Facing questions from congressional politicians, Mueller said he spoke with Trump about the FBI job before he was named as the special counsel, but "not as a candidate".
Then-White House chief strategist Steve Bannon has said that while the White House invited Mueller to speak to the president about the FBI and thought about asking him to become director again, Mueller did not come in looking for a job.
Trump tweeted on Wednesday that there are "numerous witnesses", including Vice President Mike Pence, who could say that Mueller applied and interviewed for the job and was "turned down" for it.
Pence spokesperson Alyssa Farah told the Associated Press news agency that the vice president "was present in the Oval Office when Robert Mueller interviewed for the job of FBI Director in May of 2017".
Mueller on Trump's desire to fire him
Citing his office's report, Mueller said that Trump wanted to fire him because he was investigating obstruction of justice.
Asked at a US House hearing whether Trump wanted Mueller fired for investigating possible obstruction of justice by Trump or his associates, Mueller referred to his report on the investigation and replied, "That's what it says in the report, yes. I stand by the report."
Early strategies
As expected, Democrats have so far focused on instances laid out in the Mueller report that highlighted potential way Trump obstructed justice. They have repeatedly said they believe Mueller intended for Congress to continue probing those instances.
Republicans, on the other hand, have so far focused on Trump's presumption of innocence. It also appears Republicans are attempting to discredit the probe, and at times Mueller himself.
Who is sitting next to Mueller?
Who is sitting next to Mueller, seen pointing to specific passages in what appears to be the 448-page report?
That is Mueller's top aide, Aaron Zebley. The aide was not sworn in before the House Judiciary Committee, and therefore won't testify. But according to US media, Zebley will likely be sworn in and asked questions during the House Intelligence hearing later on Wednesday. Trump called the Democrats' decision to allow Zebley to appear "a disgrace".
Mueller offers limited answers
As expected - and promised - Mueller has so far offered limited responses to committee members' questions.
He has responded to many questions with one-word answers, and referred committee members to his 448-page report.
Remember, in his opening remarks, he said he would limit his testimony to the scope of the report. "As I said on May 29, the report is my testimony," he said.
Mueller says Russia hoped to benefit from Trump
Mueller said the Russians believed they would benefit from Trump winning the 2016 presidential election.
The former special counsel was asked if his investigation found the Russian government perceived a benefit if one of the candidates won.
"Yes," he said.
"And which candidate would that be?" asked Zoe Lofgren, a Democrat.
"It would be Trump," Mueller said.
Mueller dismisses Trump's claims of 'total exoneration'
In answering questions from House Judiciary Committee Chairman Jerrold Nadler, Mueller said his report did not conclude Trump did not commit obstruction of justice.
Mueller's report said the investigation did not find sufficient evidence to establish charges of a criminal conspiracy between the Trump presidential campaign and Russia. But it said investigators did not clear Trump of trying to obstruct the probe.
Mueller: Russian interference 'among most serious' challenges
As he wrapped up his opening statement, Mueller said that Russian interference in the 2016 election is "among the most serious" challenges to American democracy.
"This deserves the attention of every American," he added.
Mueller: Won't comment on actions taken by Barr
In his opening statement, Mueller said he would not comment on any actions taken by Attorney General William Barr or Congress.
He stayed in line with what his office laid out in its report. "As I said on May 29, the report is my testimony," he said.
Mueller sworn in
Mueller has been sworn in. The former special counsel will now give his opening statement.
Nadler: We have a responsibility
In his opening remarks, House Judiciary Chairman Jerrold Nadler, a Democrat, said that Congress has a "responsibility to address the evidence" that Mueller uncovered.
"We will follow your example, Director Mueller," Nadler said. "We will act with integrity. We will follow the facts where they lead. We will consider all appropriate remedies. We will make our recommendation to the House when our work concludes."
House Judiciary Committee hearing begins
The first of the two back-to-back hearings has started. The hearing will start with committee chairman Jerrold Nadler giving his opening statement.
Mueller testimony: What to expect
As Mueller gets ready for his day of testimony, here are six things to know before the highly-anticipated hearings.
Also get a refresher on some of the key findings of the Mueller report.
And a reminder of all the key players.
Tuesday, July 23
McConnell won't watch Mueller testimony
Senate Majority Leader Mitch McConnell said he doesn't intend to watch former Special Counsel Robert Mueller give evidence before Congress on Russia's interference in the 2016 election.
The Republican told reporters on Tuesday the public already has a "pretty full picture" of Mueller's report.
McConnell said he doesn't know "how many times we want to see this movie again." He said the public has "moved on past" it.
Mueller wants aide with him
Mueller has requested that a longtime associate appears alongside him when he testifies to Congress on Wednesday.
Mueller has asked that Aaron Zebley, his former chief of staff and his top aide on the Russia investigation, accompany him at the witness table during Wednesday's hearing. That's according to a person familiar with the negotiations who requested anonymity to discuss the matter.
Republicans are opposed to the request.
Representative Doug Collins, the Judiciary panel's top Republican, called the move an "apparent stunt" by Democrats. He said it "shows the lengths Democrats will go to protect a one-sided narrative from a thorough examination by committee Republicans." Trump also criticised the move.
DOJ tells Mueller to keep to report
The Justice Department has told former Special Counsel Robert Mueller not to stray beyond his report on Russian election interference when he testifies to Congress on Wednesday.
The department said in a letter that Mueller should not speak about redacted material from his report - including material pertaining to pending criminal prosecutions, "uncharged third-parties" and "executive privilege," such as "presidential communications privileges."
The letter is entirely in line with what Mueller has already said - which is that he doesn't intend to speak beyond his report's findings during Wednesday's congressional hearings. But Democrats are preparing questions to highlight the report's most damning details.
The department provided the letter on Monday in response to what it said was a request from Mueller about limitations or potential privilege issues affecting his testimony.
