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.

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.

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) The “crime” issue

One of the key lines of Mueller’s statement in May following his report 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 US 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) Obstruction

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) 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) Anti-Trump bias

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.