The Democratic chairman of the House Homeland Security committee accused Donald Trump in a federal lawsuit on Tuesday of inciting the deadly insurrection at the US Capitol and of conspiring with his lawyer and extremist groups to try to prevent Congress from certifying the results of the presidential election he lost to Joe Biden.
The lawsuit from Representative Bennie Thompson of Mississippi is part of an anticipated wave of litigation connected to the riot on January 6 riot.
It is believed to be the first filed by a member of Congress. It seeks unspecified punitive and compensatory damages.
The case also names as defendants the Republican former president's personal lawyer Rudy Giuliani and extremist groups including the Proud Boys and the Oath Keepers, some of whose members have been charged by the Justice Department with taking part in the siege.
Trump adviser Jason Miller said on Tuesday that Mr Trump did not organise the rally that preceded the riot and “did not incite or conspire to incite any violence at the Capitol on January 6.”
A lawyer for Mr Giuliani did not return an email seeking comment.
The suit, filed in federal court in Washington under a post Civil War Reconstruction-era law known as the Ku Klux Klan Act, came three days after Mr Trump was acquitted in a Senate impeachment trial that centred on allegations that he incited the riot in which five people died.
That acquittal is likely to open the door to more legal scrutiny over Mr Trump’s actions before and during the siege.
Additional suits could be brought by other members of Congress or by law enforcement officers injured while responding to the riot.
Even Republicans who voted to acquit Mr Trump on Saturday acknowledged that the more proper venue to deal with Mr Trump was in the courts, especially now that he has left the White House and lost certain legal protections that shielded him as president.
The suit traces the drawn-out effort by Mr Trump and Mr Giuliani to cast doubt on the election results even though courts across the country and state election officials repeatedly rejected their allegations of fraud.
Despite evidence to the contrary, the suit said, the men portrayed the election as stolen while Mr Trump “endorsed rather than discouraged” threats of violence from his angry supporters in the weeks leading up to the assault on the Capitol.
“The carefully orchestrated series of events that unfolded at the Save America rally and the storming of the Capitol was no accident or coincidence,” the suit said.
“It was the intended and foreseeable culmination of a carefully co-ordinated campaign to interfere with the legal process required to confirm the tally of votes cast in the Electoral College.”
Presidents are historically afforded broad immunity from lawsuits for actions they take in their role as commander in chief. But the lawsuit filed on Tuesday was brought against Mr Trump in his personal, not official, capacity and alleges that none of the behaviour at issue had to do with his responsibilities as president.
“Inciting a riot, or attempting to interfere with the congressional efforts to ratify the results of the election that are commended by the constitution, could not conceivably be within the scope of ordinary responsibilities of the president,” Joseph Sellers, a lawyer for Mr Thompson, said in an interview.
“In this respect, because of his conduct, he is just like any other private citizen,” he said.
Mr Sellers, a lawyer with the Washington law firm of Cohen Milstein, filed the case along with the NAACP.
Several other members of Congress were expected to join.
Although the impeachment case focused squarely on accusations of incitement, the lawsuit more broadly accuses Mr Trump of conspiring to disrupt the constitutional activities of Congress — namely, the certification of election results establishing Biden as the rightful winner — through a lengthy effort to discredit the outcome and to lean on individual states and his own vice president to overturn the contest.
The case against Mr Trump was brought under a provision of the Ku Klux Klan Act of 1871, which sought to prohibit violence or intimidation meant to prevent Congress or other federal officials from carrying out their constitutional duties.
“Fortunately, this hasn’t been used very much,” Mr Sellers said. “But what we see here is so unprecedented that it’s really reminiscent of what gave rise to the enactment of this legislation right after the Civil War.”
The suit cites incendiary comments that Mr Trump and Mr Giuliani made in the weeks leading up to the riot and on the day of it that lawyers say were designed to mobilise supporters to work to overturn the election results and to prevent the congressional certification process. That process was temporarily interrupted when Trump loyalists broke into the Capitol.
Mr Trump told supporters at a rally preceding the event to “fight like hell,” but lawyers for the former president denied during the impeachment trial that he had incited the riot.
They said during his speech he told the crowd to behave “peacefully” that day.
Defence lawyers were likely to revisit those assertions in the lawsuit. They may also argue, as was done during the impeachment case, that Mr Trump's speech was protected by the First Amendment.