Former FBI director Robert Mueller, who led the 22-month investigation into Russian interference in the 2016 US presidential election, will appear before two congressional committees on Wednesday.

His testimony is one of the most highly anticipated events in Washington since the beginning of the Trump presidency in 2017.

Mueller, however, is heading to Capitol Hill reluctantly. In a press conference of May 29th – his first public comments since he was appointed special counsel to lead the Russia investigation in May 2017 – he expressed the hope that he was making his final statement on the matter, adding that any congressional testimony “would not go beyond” what was contained within his 448-page report.

His report, which said he had not found sufficient evidence to establish a conspiracy between Russia and Donald Trump’s election campaign, was completed in March. The report did not reach a conclusion on whether Mr Trump had attempted to obstruct justice.

Mueller is well-experienced when it comes to testifying before Congress due to his prior experience in the FBI. Wednesday’s appearance will be the 89th time he was been questioned by lawmakers.

Few bombshells

Officials on Capitol Hill have been trying to dampen expectations. The sense that the hearings – which will be spread across the morning and afternoon – will contain few bombshells was underlined this week by a letter from the department of justice to Mueller warning him to stay within the bounds of his report.

Nonetheless Democrats will have an important opportunity to get Mueller on the record, and more importantly ensure that his words are witnessed by millions of Americans.

“We want Robert Mueller to bring it to life,” said House intelligence committee chairman Adam Schiff this weekend, noting that many people had not read the Mueller report, a legalistic and highly dense piece of work. As others have put it this week, “Seeing the movie is different than reading the book.”

The stakes could not be higher for Democrats as they deal with an increasingly tense split within their own party over whether to move forward with impeachment hearings against Trump.

Impeachment

A motion brought to the House floor last week saw most Democrats side with Republicans to block a vote on impeachment, though more than 90 Democrats voted in favour – a sizeable minority. House speaker Nancy Pelosi is among those cautioning against impeachment, amid concern that it could backfire if there is insufficient support among the American public.

The political reality is that Republicans control the Senate, meaning that Trump is unlikely to be convicted if an impeachment trial is held.

As a result Wednesday’s testimony will have a major impact on whether the Democratically-controlled House of Representatives decides to begin impeachment proceedings against the president, or continue with its own committee investigations into the president’s conduct.

Here are some of the questions Mueller may face when more than 63 lawmakers from the judiciary and intelligence committees question him during approximately five hours of testimony:

1) One of the key lines of Mueller’s May 29th statement was the following: “If we had had confidence that the president clearly did not commit a crime, we would have said so.” He also pointed out that department of justice guidelines prevented him from making a judgment. Democrats are expected to press Mueller on this statement, and specifically whether he would have charged the president if those department of justice guidelines did not exist.

2) Did the president obstruct justice? Democrats are likely to focus on the Mueller report’s interview with former White House counsel Don McGahn, particularly his contention that Trump asked him to fire Mueller and then asked him to change the record to hide this fact.

3) Donald Trump jnr. Democrats are likely to focus on the president’s eldest son, who attended the infamous June 2016 meeting in Trump Tower with Russian individuals. Trump jnr was not questioned by the special counsel. Some members of Congress want to know why.

4) Suggestions of possible witness tampering. Did Donald Trump dangle the possibility of presidential pardons before witnesses such as Paul Manafort and Michael Cohen to discourage them from co-operating with investigators?

5) Republicans on the committees will likely focus on what many believe is an anti-Trump bias at US intelligence agencies. This will include the anti-Trump text messages exchanged by FBI employees Peter Strzok and Lisa Page, as well as the rationale for attaining a warrant to wiretap former Trump aide Carter Page during the presidential campaign.