When Donald Trump attacks the integrity of judges hearing cases against him, his followers often respond with posts urging that the jurists be beaten, tortured and killed.

On a recent Tuesday morning, a visibly frustrated Donald Trump sat through a tense hearing in the first-ever criminal trial of a former American president. During a break, he let rip on his social media platform.

New York Justice Juan Merchan, Trump declared on Truth Social, is a “highly conflicted” overseer of a “kangaroo court.” Trump supporters swiftly replied to his post with a blitz of attacks on Merchan. The comments soon turned ugly. Some called for Merchan and other judges hearing cases against Trump to be killed.

“Treason is a hangable offence,” one wrote.

“They should all be executed,” added another.

The April 23 post by Trump and the menacing responses from his followers illustrate the incendiary impact of his angry and incessant broadsides against the judges handling the criminal and civil suits against him. As his presidential campaign intensifies, Trump has baselessly cast the judges and prosecutors in his trials as corrupt puppets of the Biden administration, bent on torpedoing his White House bid.

This judge must be arrested the minute Trump is inaugurated.

Yep, I hope Trump has that judge hanged for Treason.

Judge needs a hatchet to the face.

And his whore daughter!

Comments calling for violence against judges handling Donald Trump’s legal cases regularly appear on the pro-Trump website Patriots.Win, typically in response to posts echoing his attacks on the jurists’ integrity.

The rhetoric is inspiring widespread calls for violence. In a review of commenters’ posts on three pro-Trump websites, including the former president’s own Truth Social platform, Reuters documented more than 150 posts since March 1 that called for physical violence against the judges handling three of his highest-profile cases – two state judges in Manhattan and one in Georgia overseeing a criminal case in which Trump is accused of illegally seeking to overturn the state’s 2020 election results.

Those posts were part of a larger pool of hundreds identified by Reuters that used hostile, menacing and in some cases, racist or sexualised language to attack the judges, but stopped short of explicitly calling for violence against them.

Experts on extremism say the constant repetition of threatening or menacing language can normalise the idea of violence – and increase the risk of someone carrying it out.

Mitch Silber, a former New York City Police Department director of intelligence analysis, compared the Trump supporters now calling for violence against judges to the US Capitol rioters who believed they were following Trump’s “marching orders” on January 6, 2021.

“This is just the 2023-2024 iteration of that phenomenon,” Silber said. “Articulating these ideas is the first step along the pathway of mobilising to violence.”

Trump spokesperson Steven Cheung did not respond to specific questions about the posts. Trump, the presumptive Republican presidential nominee, has a right to criticise what he called “un-Constitutional witch hunts,” Cheung said. He also asserted, without citing examples, that Trump has been the target of calls for “despicable violence” from “Democrats and crazed lunatics.”

When Trump posts attacks on the judges hearing cases against him, followers on his Truth Social media platform sometimes reply with memes suggesting the judges be killed or tortured.

On Patriots.Win, an online forum that describes itself as Trump’s “community of choice,” Trump’s attacks on courts and judges regularly spur calls for violence. Merchan “needs to be strangled with piano wire,” one poster wrote. He “deserves garrotting in the street,” wrote another.

The Gateway Pundit, a website influential in the pro-Trump community, is also a frequent venue for Trump-inspired violent rhetoric against judges hearing his cases. “These judges and lawyers should HANG for perpetuating these fraud cases,” a commenter wrote on April 16, suggesting the executions would be “an example for future generations of judges and lawyers.”

The Federal Bureau of Investigation and the New York Police Department declined to comment on whether any threatening posts directed at the New York judges were under federal or local investigation.

While Trump himself hasn’t called for violence on judges, his language can signal to followers that judges are no different from partisan rivals worthy of scorn, derision and attack, threatening the legitimacy of the independent judiciary, said experts on political violence.

“Trump is constantly riling up his supporters to be angry on his behalf,” said Lilliana Mason, a John Hopkins University political scientist. “He takes that large group of angry people; he points them in a particular direction and then the judges get all these death threats.” Cheung had no response to that analysis.

The posts also illustrate a shift in the way violent language is being expressed online by Trump’s followers. In 2021, Reuters documented a wave of threats by Trump supporters targeting US. election workers. Legal experts found that many had met the legal standard for prosecutable threats, which typically requires language or context that reflects a clear intent to act or instil fear, rather than simply suggesting a frightening outcome.

“Trump is constantly riling up his supporters to be angry on his behalf. He takes that large group of angry people; he points them in a particular direction; and then the judges get all these death threats.”

In contrast, the current barrage of pro-Trump threats generally stop short of that red line. Posters often call for violence – without explicitly stating they intend to commit it themselves. Such language is usually defensible as constitutionally protected free speech. But experts say it can have the same effect as a direct threat: to intimidate and sow fear.

• A Reuters report