CATCH UP: Where we are and what's next for all the Trump-Russia investigations
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On Friday, Trump shot back, denying Comey's allegations and accusing the former FBI head of lying under oath.
Despite the president's alleged attempts to stymie them, several investigations into Russian interference in the 2016 election and possible collusion between the Trump campaign and Russian officials continue - perhaps with renewed vigor.
These are the related but separate investigations underway.
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The Justice Department investigation
After Democratic outrage over Comey's ousting and leaks about his allegations against Trump, the Justice Department appointed a special counsel, former FBI Director Robert Mueller, to lead the department's investigation into "any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump."
Mueller - with the help of FBI investigators and DOJ lawyers - will also investigate whether any crimes, including obstruction of justice, witness intimidation, or perjury, were committed by anyone involved in the inquiry - including Trump.
While Mueller still technically reports to the Trump administration (he was hired, and could be fired, by Deputy Attorney General Rod Rosenstein), it would trigger enormous political backlash if the DOJ were seen to be interfering in the special counsel's inquiry.
"The incentives are in place for the special counsel to appear to be conducting a thorough and well-resourced investigation," Lisa Kern Griffin, a professor of law at Duke, told Business Insider.
Mueller, who is widely respected, was likely chosen for his 12-year tenure running the FBI under both Republican and Democratic presidents. Given that he reports to and receives funding from the administration, there is a certain degree of trust the public must place in Mueller's ability to remain independent from the president and his administration.
"Given his qualifications, his reputation, his enormous talent, his undisputed patriotism and the structure of the office he's set up, it's fair to say that he's going to be very independent," Griffin said.
But independence is not guaranteed, and whether Mueller's investigation is compromised in any way will not necessarily become known to the public.
"We certainly have no idea whether anybody behind the scenes is telling him not to do anything, we just don't know," Richard Briffault, a professor at Columbia law school, told Business Insider.
"We have to trust in his [willingness] to resign and or go public should he feel that he is not being given adequate independence."
According to Griffin, there isn't a clear way Mueller could come forward if he experienced administration interference while conducting the investigation.
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If Mueller finds evidence of criminal activity, he could seek to indict members of the Trump campaign, including, theoretically, Trump himself.
But an American president has never before been criminally charged, and it's very unlikely that situation could arise, in part because prosecution is a function of the executive branch, and the president runs that branch.
"I can't see any circumstances in which a criminal prosecution would be brought," Peter Schuck, a professor of law emeritus at Yale, told Business Insider.
Even if the president shot someone in the street, he or she would likely be impeached before facing criminal charges.
The Senate and House Intelligence Committee investigations
Both the Senate and House are pursuing wide-ranging investigations that cover more ground than the justice department investigation. The congressional inquiries are looking into the Russian interference in the 2016 election, and possible ties between the Trump campaign and Russian officials, the circumstances surrounding Comey's firing, and leaks of classified information.
While Mueller and the FBI's investigations will be conducted behind closed doors, the congressional investigators can hold public hearings.
While Congress doesn't have any power to prosecute, if the committees uncover criminal activity, Congress can hold a vote to impeach the president.
"Ultimately, the president's jeopardy isn't so much legal - it's political," Griffin said.
The House would vote to impeach the president, which is akin to an accusation. Then, the house would act as the prosecution in a senate trial. It's up to senators to decide a president's guilt.
But many say that without a majority of Democrats in Congress, impeachment would be unlikely.
"There's not going to be an impeachment at this point, in this Congress, unless fellow Republicans get really sick of him and there's no sign that that's happening," Charles Fried, a law professor at Harvard and former solicitor general under President Ronald Reagan, told Business Insider.
The Senate Judiciary and House Oversight and Government Reform Committees
Two other Senate and House committees - the Senate Judiciary and House Oversight and Government Reform committees - are also investigating whether Trump committed obstruction of justice when he asked Comey to drop the FBI's investigation into Flynn and his subsequent firing of Comey.
Obstruction of justice occurs when someone acts with corrupt intent while attempting to intervene in the administration of justice.
In addition, the committees are looking into Flynn's ties to foreign powers, including Russia.
Like with the intelligence committee investigations, these inquiries could lead to more public hearings and, if Congress concludes that Trump broke the law, it could lead to impeachment.
No end in sight
Despite the hearings, revelations, and leaks, it will likely be a long time before any conclusions are drawn from the investigations, Griffin says.
"A white-collar case of this type, even without the national-security dimensions, the international financial evidence, the context of electoral politics, would ordinarily take years for federal agents to investigate," Griffin said, adding that this case involves more urgency and resources than others.
"It will be months, maybe even years, before they reach any definitive conclusions."
But the length of the investigations could create its own obstacle.
"Presumably, the White House could at some point say, 'You've had a year, you've had two years, it's over,'" Briffault said.
And the fact that so many investigations are being pursued simultaneously will likely complicate matters.
"It is unfortunate because they'll get in each other's way," Fried said.
Ideally, he said, there would be "one bipartisan select committee of congressmen and senators."
But Republican lawmakers are far from agreeing to the creation of a special committee, so it's no surprise there are so many investigators on the Hill.
"Everybody wants to get into the act - it is Washington," Fried said.