Could Trump be prosecuted for inciting the attack on Capitol Hill?

US President Donald Trump is unlikely to face criminal charges in connection with the violent siege on the US Capitol last week because of the country's broad free speech protections, some legal experts said.

Here's an explanation of why lawyers, including ones who think Trump should be impeached for his remarks, say such a case would be an uphill battle for prosecutors.

Read | The peculiar paradox of American democracy

What did Trump say in his speech?

For over two months, Trump has falsely claimed that the Nov. 3 election was marred by widespread fraud and has tried to subvert the electoral process.

On Jan. 6, as lawmakers were certifying Democrat Joe Biden’s victory, Republican Trump took to a stage near the White House and exhorted a crowd of supporters repeatedly to “fight” - using the word more than 20 times - and “not take it any longer.”

Trump told the crowd they must “be strong” before instructing the “patriots” on a march to the Capitol. "After this, we’re going to walk down and I’ll be there with you," Trump said.

At one point in the speech, Trump told the crowd they should “peacefully and patriotically make your voices heard."

Trump returned to the White House after the remarks and reportedly watched the attack on television.

He has since disavowed any responsibility for the storming of the Capitol, telling reporters his words have been analyzed "and everybody ... thought it was totally appropriate."

What crimes could Trump be charged with?

There is a chapter of US law dealing with "subversive activities."

One federal law makes it a crime to engage in “rebellion or insurrection" against the federal government.

Another statute, known as seditious conspiracy, prohibits conspiracies to "overthrow" the US government or seize government property by force.

The District of Columbia has its own criminal code, which says anyone who "willfully incites or urges other persons to engage in a riot" shall face a fine or up to 180 days in prison.

What would Trump's defense be?

Trump would have a strong argument that he engaged in free speech protected by the First Amendment of the US Constitution, legal experts said.

Trump can argue that his rhetoric was sufficiently ambiguous, and that when he said "fight" he did not mean attack the Capitol, they said.

In a seminal 1969 case, the Supreme Court overturned the conviction of an Ohio Ku Klux Klan leader, Clarence Brandenburg, for his brief speech at a rally urging a dozen followers to go to Washington and attack politicians.

The court said prosecutors have to prove speech is directed at inciting "imminent lawless action" and it has to be likely to produce that action.

"My own tentative view is that it was First Amendment protected speech and therefore it should not be subjected to criminal liability," said Ilya Somin, a law professor at George Mason University, adding that Trump's rhetoric was still grounds for impeachment by Congress, considering his position as an elected official.

Paul Smith, a lawyer who has argued for liberal causes at the US Supreme Court, said the Brandenburg case shows Trump's speech was constitutionally protected.

"If he was there with a bullhorn in the outside yard of the Capitol and urging people to charge the windows and break them and take Congress hostage, in that situation he would be responsible for what the crowd did," said Smith.

An FBI office in Virginia warned that extremists planning to travel to Washington were talking of "war," according to a report in the Washington Post.

If Trump knew of the report or recklessly ignored it, it would increase the likelihood a prosecutor would charge him, said Alexander Tsesis, a professor with Loyola University School of Law in Chicago

Prosecutors would still need to prove beyond a doubt that Trump intended to incite the crowd to violence and that illegal activity was imminent and likely.

To bring a seditious conspiracy case, prosecutors would need more information about the activities of the president leading up to, during and after the violence to determine whether he had knowledge of a planned attack or provided assistance, said legal experts.

Is prosecution likely?

Based on currently public information, legal experts doubt the incoming Biden administration would pursue a former president. The move could risk distracting the new government and touch off a political storm in a divided United States.

Biden has previously said a prosecution of Trump would be bad for the country, but that he would not interfere with the Justice Department's decision-making.

A top prosecutor in the District of Columbia, Ken Kohl, on Jan. 8 told reporters that he did not expect to see a criminal case against Trump for inciting violence.

Smith said he thought the Biden administration would be wary of bringing a "prosecution that pushes the boundaries of constitutional law" right after taking over from Trump. "That would be pretty aggressive."