The Trump campaign’s alleged links to Russia are to be investigated by an ex-FBI chief, who has been appointed as special counsel. But what does the role involve?
Robert Mueller’s appointment follows President Donald Trump’s shock sacking of FBI director James Comey, who had previously been looking into the claims.
What is a special counsel?
Mr Mueller, a lawyer who headed the FBI between 2001 and 2013, was appointed special counsel by the US Department of Justice on Wednesday.
A special counsel is named when there is a conflict of interest for the normal prosecuting body.
For example, any government official investigating a president is effectively probing their own boss, so special counsels (or prosecutors) have traditionally been appointed to look at allegations regarding the White House.
Is a special counsel different to a special prosecutor?
Yes and no. They basically do the same thing, but have slightly different reporting lines. Between the last 1970s and 1999 special prosecutors reported to an independent commission set up by Congress.
In this case the special counsel will report directly to the Department of Justice, which itself reports to President Trump.
What powers does a special counsel have?
A special counsel has the freedom to look at anything they believe is relevant to their investigation.
Although there are already four committees in the US Congress looking at alleged links between Mr Trump’s team and Russia, their focus is limited to only the brief of the particular committee.
Mr Mueller can probe possible links or coordination between Mr Trump’s campaign team and the Russian government, along with “any matters that arose or may arise directly from the investigation”, the letter announcing his appointment states.
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He is also authorised to prosecute federal crimes arising from his investigation.
But, despite the wide scope of his role, Mr Mueller must ask for permission to expand his investigation should he want to look at anything he believes to be outside of the remit of the letter appointing him.
Mr Mueller will enjoy the full power to begin investigations and force the release of documents, while he can appoint his own staff who will report to no one else but himself.
He will have to suggest a budget for his investigation within the next two months.
Mr Mueller will also only have to inform the Justice Department what he is up to when he chooses, although the attorney-general should be told of “significant” actions.
In the case of Russia, Mr Mueller will report to deputy attorney general Rod J Rosenstein, who appointed him, after attorney general Jeff Sessions was forced to step away from any Russia-linked probes earlier this year.
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It followed claims Mr Sessions himself had been in contact with Russian officials during last year’s election campaign.
Mr Mueller will hand a confidential report to Mr Rosenstein when he finishes his investigation but the contents of that report will not necessarily be made public.
What previous special prosecutors have there been?
There are numerous historical examples of a special prosecutor being appointed to probe claims of government or presidential wrongdoing.
Most famously, a special prosecutor was tasked with investigating the Watergate scandal in the 1970s, which led to Richard Nixon’s resignation as president.
Special prosecutor Kenneth Starr led the Whitewater probe into business investments by Bill and Hillary Clinton in the 1990s.
This later turned into an investigation into Mr Clinton’s denial of an affair with White House aide Monica Lewinsky.
Both Watergate and Whitewater led to impeachment proceedings against the serving president.
In 1986, a special prosecutor found Ronald Reagan’s staff had illegally sold arms to Iran as part of the Iran-Contra scandal.
Earlier in US history, the Teapot Dome bribery scandal in the early 1920s and the 1875 siphoning of millions of tax dollars by the Whiskey Ring group of politicians were both investigated by special prosecutors.
Can the president sack a special counsel?
Mr Trump can’t sack a special counsel although Mr Rosenstein – who was nominated for his role by the President and helped work on the sacking of Mr Comey – could dismiss Mr Mueller.