After voting to acquit Donald Trump of inciting an insurrection, Mitch McConnell hinted that the former president’s legal woes were far from over.

“We have a criminal justice system in this country,” said the Senate minority leader on Saturday night. “We have civil litigation. And former presidents are not immune from being held accountable by either one.”

He echoed other Republican senators, including Florida’s Marco Rubio, who have suggested Trump could soon face charges in criminal or civil courts relating to the January 6 siege on the US Capitol.

Critics have accused Republican lawmakers of shirking responsibility by refusing to convict the former president of inciting an insurrection over the siege.

But legal experts agree that Trump, who is already facing a criminal investigation in Manhattan relating to financial dealings at the Trump Organization, is likely to find himself at the centre of several more probes. Now that he is a private citizen, he no longer enjoys the legal protections afforded to him when he was president.

Noah Bookbinder, executive director of Citizens for Responsibility and Ethics in Washington, said: “This trial and the Senate’s vote is incredibly important, but I don’t think that it will be or should be the only avenue for accountability for Donald Trump.”

Bookbinder’s group has filed a criminal complaint with the Department of Justice and Fani Willis, the district attorney of Fulton County, Georgia. Willis has launched an investigation centred on Trump’s now-infamous phone call to Brad Raffensperger, Georgia’s Republican secretary of state. In that phone call, the audio of which was published by the Washington Post, Trump pressured Raffensperger to “find” enough votes to help him win the presidential election there. House impeachment managers, acting as prosecutors in the Senate impeachment trial, cited the call in making their case.

Willis told MSNBC her investigation “seems that it will go past just this one phone call”.

“Whether there was an impeachment or not an impeachment would not change the fact that something occurred here within my jurisdiction that may be criminal. And if that is the case, it needed to be investigated.”

CREW’s complaint alleges that Trump had “illegally conspired to deprive the people of Georgia of their right to vote and have their votes counted”, conspired to “intimidate” Georgia election officials to falsify the vote count and tried to cause them to “engage in conduct that constitutes a crime under the state election code.”

He has also been accused of pressuring election officials in several other states to overturn the results of November’s presidential election, including in Arizona, Michigan and Pennsylvania. Legal experts say the case in Georgia is the most compelling at this stage, given the incriminating nature of the Raffensperger call that is already in the public domain.

“There is serious risk under Georgia law for the president, including because the call was recorded, so there is such damning evidence,” said Norm Eisen, White House ethics tsar under Barack Obama who served as counsel to the Democrats in Trump’s first impeachment. Trump was first impeached in 2019 over his efforts to pressure the Ukrainian president to dig up dirt on Joe Biden, though he was also exonerated by the Senate on those charges after Mitt Romney was the only Republican who voted to convict.

“Among the many potential criminal issues that are raised by the president’s Georgia call are solicitation of election fraud . . . it raises issues of conspiracy under Georgia law, intentional interference with election duties, false statement issues, betrayal of oath, potential racketeering issues . . . There is a lot of criminal exposure,” Eisen said.

“If I were Donald Trump, I would be very, very worried.”

Meanwhile, Trump could also face charges in the District of Columbia, where federal prosecutors are in the middle of a sweeping investigation into the January 6 riots that left five people dead. More than 200 people have already been charged with federal crimes for their participation in the siege, and Karl Racine, the DC attorney-general, has left the door open to investigating and possibly charging Trump for inciting the violence.

Trump has denied any wrongdoing and dismissed the legal efforts against him, along with his impeachment, as part of “the greatest witch hunt in the history of our country”.

Legal experts warn that the legal standard for criminal incitement sets a high bar that would make it an uphill battle for lawyers to prove Trump’s guilt. This is in part due to the strong protections the First Amendment provides for free speech in the US. In the landmark 1969 ruling in Brandenburg vs Ohio, the US Supreme Court established a two-pronged test that determined that speech could be prohibited if it were “directed to inciting or producing imminent lawless action and is likely to incite or produce such action”.

“It is just a very high standard,” said Alan Rozenshtein, a professor at University of Minnesota Law School and a former DoJ lawyer.

“If we allowed incitement prosecutions every time someone called for a protest that became a riot, we would have a lot more incitement prosecutions,” he explained. “I don’t think folks on the political left, especially given the unrest we saw over the summer, want to go down that path.”