On 20 January 2021, Joe Biden was inaugurated as the 46th president of the United States with a record 81 million votes - the most of any president -following a tightly contested election plagued with baseless and now disproven rumours of widespread voter fraud.

Donald Trump, who was impeached for the second time following the Capitol insurrection many say he incited, was acquitted by the Senate after they failed to secure a two-thirds majority to convict.

Following the acquittal, a new question in the minds of Americans began to arise: could the former president face criminal prosecution?

According to legal experts, the answer is complicated. Many say it would be an uphill battle for many prosecutors due to the country’s broad free speech laws.

To understand the difficulties, it's best to start with some context.

As the 2020 presidential election began winding down, with Joe Biden emerging as the clear winner, then-President Trump and his close allies began spreading rumours, seeking to undermine public confidence in the electoral process.

What followed was more than two months of attacks on various facets of the U.S. electoral process, including mail-in ballots, voting machines and poll workers. Rallying calls such as "stop the steal" came to relative infamy.

A recent National Intelligence report has shown they were assisted in their efforts by the Russian government.

By 6 January, as lawmakers voted to certify Mr Biden’s election victory, Mr Trump took the stage at a large rally just blocks away from the Capitol. Speakers included Rudy Giuliani, Madison Cawthorn and Lara Trump. Mr Giuliani called for attendees to engage in “trial by combat”, while Mr Trump encouraged his supporters to “walk down to the Capitol” and “fight like hell”.

"You'll never take back our country with weakness. You have to show strength and you have to be strong. We have come to demand that Congress do the right thing and only count the electors who have been lawfully slated," he said.

Mr Trump returned to the White House and reportedly began watching what would unfold on television - the most prolific attack on the Capitol to date, which ended with five people dead, including a Capitol Police officer.

The 74-year-old former president later denied any responsibility for the attacks and condemned what took place.

U.S. federal law makes it a crime to engage in “rebellion or insurrection” against the government. Conspiracies to overthrow the U.S. government are also crimes.

The District of Columbia also has its own statutes, with one area stating anyone who incites or urges others to riot will face a fine or up to 180 days in prison.

But these laws may not stick in court, legal experts say. Mr Trump has a strong, wide-ranging argument to say he engaged in free speech, as defined in the first amendment of the U.S. Constitution, as he never explicitly told anyone to riot - at most, he hinted at it (though this can be just as harmful).

Experts told Thomson Reuters that the former president's legal team can make the argument that his rhetoric was “ambiguous” and that by “fight”, he didn’t mean storm the Capitol. Prosecutors have to prove that speech is directed in an attempt to incite “imminent lawless action”.

According to Alexander Tsesis, a law professor at the Loyola University School of Law in Chicago, Mr Trump could be prosecuted if evidence could be found that he knew of - and willfully ignored - a Virginia FBI report warning of extremists heading to Washington.

Ultimately, federal lawyers would need detailed evidence of Mr Trump’s activities before, during and after the rioting at the Capitol to press any charges.

D.C. prosecutor Ken Kohl told the press on 8 January that he didn’t expect criminal charges to be filed against Mr Trump, citing the cautious Biden administration as well as the burden of proof required for trials.

Mr Kohl described the idea of a Trump prosecution as one that “pushes the boundaries of constitutional law” and went on to say the move would be “pretty aggressive”.