Why was Donald Trump under investigation by the FBI and Robert Mueller and what does obstruction of justice mean?
US PRESIDENT Donald Trump was the subject of an intense FBI investigation which ultimately found no evidence of collusion with Russia.
Ex-FBI boss Robert Mueller was leading the inquiry, but what did his probe involve?
Who is Robert Mueller?
Robert Mueller III, 73, led the FBI from September 2001, days before 9/11.
The FBI chief from New York City stepped down from his director role in September 2013.
He was succeeded by James Comey, who was sacked in May 2017 by President Trump while leading an investigation into alleged Russian links to the Trump campaign.
This overall investigation was passed on to Mueller, now special counsel of the Justice Department.
Why was Donald Trump under investigation?
Trump found out he was being investigated by the FBI on his birthday, June 14, in 2017.
In the run-up to the probe's second anniversary, Trump tweeted: "This is the single greatest witch hunt of a politician in American history!"
Robert Mueller was investigating whether there was collusion between the Russian government, its agencies or affiliates, and the Trump campaign.
It is already the established view of the United States that Russia intervened in the election through a massive overt online propaganda campaign and covert means to influence the election in favour of Donald Trump.
The aim of Muller's investigation was to discover whether this effort was coordinated or aided by the Trump team.
In April 2018, Mueller told Trump's lawyers that he was continuing to investigate the president but did not consider him a criminal target in the Russia probe "at this point," the .
On March 24, Mueller's report concluded that there was no evidence of collusion between Trump's campaign and Russia.
Trump welcomed the news on Twitter with: "No Collusion, No Obstruction, Complete and Total EXONERATION. KEEP AMERICA GREAT!"
Mueller's report does not actually exonerate Trump, however.
How did Jeff Sessions' resignation impact Mueller's investigation?
On Wednesday, November 7, 2018, Jeff Sessions resigned at the behest of the President.
This led to speculation that Trump's real target was Mueller and his Russia investigation.
Congressman Jerry Nadler, the incoming chairman of the judiciary committee, said in a statement: “There is no mistaking what this means, and what is at stake: this is a constitutionally perilous moment for our country and for the president.”
Sessions' temporary replacement Matthew Whitaker has criticised the investigation, of which he will have direct oversight, saying in 2017 that it overstepping its bounds.
What does obstruction of justice mean?
Trump could be charged with obstruction of justice if he is found to have tried to influence Comey into dropping the Flynn-Russia investigation.
Obstruction of justice means trying to block, prevent or hinder prosecutors from carrying out their jobs.
Usually this means witnesses lying to investigators — but it can also cover a person wilfully trying to protect a suspect by hiding evidence or trying to deter an investigation.
If, as reported, Mueller is indeed assessing whether or not Trump obstructed the course of justice and the President is charged, Congress could be moved to impeach him.
The Democrats won the majority of the House of Representatives in the midterms on Wednesday, November 6, so the chance of Trump being impeached has dramatically increased.
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What impact did the jailing of Michael Cohen - Trump's former lawyer - have on the investigation?
Trump's former fixer and confidant Michael Cohen was jailed for three years on December 12 2018 for his role in making illegal hush-money payments to women to help Trump's 2016 election campaign and lying to Congress about a proposed Trump Tower project in Russia.
Although these crimes relate to the president, they are not evidence of collusion with Russian's over the election - the key focus of the investigation.
In order to have his sentence reduced from the recommended five years, Cohen pledged to aid investigators.
This means, if Cohen was privy to any collusion, prosecutors may have had a source to draw on.