LONDON — Julian Assange's lawyers opened a final U.K. legal challenge Tuesday to stop the WikiLeaks founder from being sent to the United States to face spying charges, arguing that American authorities are seeking to punish him for exposing serious criminal acts by the U.S. state

Lawyer Edward Fitzgerald said there is a risk Assange “will suffer a flagrant denial of justice” if he is sent to the U.S. At a two-day High Court hearing, Assange’s attorneys are asking judges to grant a new appeal, his last legal roll of the dice in Britain

Assange himself was not in court. Judge Victoria Sharp said he was granted permission to come from Belmarsh Prison, where he has been held for five years, but had chosen not to attend. Fitzgerald said the 52-year-old Australian was unwell but did not elaborate on his health.

Assange has been fighting extradition for more than a decade, including seven years in self-exile in the Ecuadorian Embassy in London and the last five years in the high-security prison on the outskirts of the British capital.

He has been indicted on 17 charges of espionage and one charge of computer misuse over his website’s publication of classified U.S. documents almost 15 years ago. American prosecutors say Assange helped U.S. Army intelligence analyst Chelsea Manning steal diplomatic cables and military files that WikiLeaks later published, putting lives at risk.

To his supporters, Assange is a secrecy-busting journalist who exposed U.S. military wrongdoing in Iraq and Afghanistan. They argue that the prosecution is politically motivated and he won’t get a fair trial in the U.S.

Hundreds of supporters holding “Free Julian Assange” signs and chanting “there is only one decision – no extradition” held a noisy protest outside the ne-Gothic High Court in London. Rallies were also held in cities around the world, including Brussels and Berlin.

Assange’s wife Stella Assange told the crowd the case was about “the right to be able to speak freely without being put in prison and hounded and terrorized by the state.”

Referring to the Russian opposition leader Alexei Navalny, who died in prison last week, she said: “What happened to Navalny can happen to Julian, and will happen to Julian if he is extradited.”

Stella Assange, who married the WikiLeaks founder in prison in 2022 — said last week that his health has deteriorated during years of confinement and "if he’s extradited, he will die.”

If the judges rule against Assange, he can ask the European Court of Human Rights to block his extradition — though supporters worry he could be put on a plane to the U.S. before that happens, because the British government has already signed an extradition order.

Assange’s lawyers say he could face up to 175 years in prison if convicted, though American authorities have said the sentence is likely to be much shorter than that.

While several of Assange’s arguments against extradition have already been rejected by British courts, his lawyers are trying to make new points to secure an appeal.

“He is being prosecuted for engaging in ordinary journalistic practice of obtaining and publishing classified information,” lawyer Fitzgerald said in court, arguing that publication of leaked documents is a common journalistic practice, protected by well-established principles of free speech.

The attorneys argued that the prosecution of Assange is politically motivated retaliation for WikiLeaks' "exposure of criminality on the part of the U.S. government on an unprecedented scale.”

“The U.S. was prepared to go to any lengths (including misusing its own criminal justice system) to sustain impunity for U.S. officials in respect of the torture/war crimes committed in its infamous ‘war on terror’, and to suppress those actors and courts willing and prepared to try to bring those crimes to account," Assange's lawyers said in written arguments. "Mr. Assange was one of those targets.”

Assange’s lawyers also want judges to reconsider allegations that the CIA developed plans to kidnap or kill Assange while he was in the Ecuadorian Embassy. A lower-court judge has dismissed the claims, but Assange attorney Mark Summers said Tuesday “there is compelling evidence now in existence that the plot was real.”

“There was a plot to kidnap Mr. Assange, to rendition him to America, or else straightforwardly murder him,” the lawyer claimed.

James Lewis, a lawyer for the U.S., said Assange was being prosecuted “because he is alleged to have committed serious criminal offences.”

He argued in written submissions that Assange’s actions “threatened damage to the strategic and national security interests of the United States” and put individuals named in the documents — including Iraqis and Afghans who had helped U.S. forces — at risk of “serious physical harm.”

Assange’s legal troubles began in 2010, when he was arrested in London at the request of Sweden, which wanted to question him about allegations of rape and sexual assault made by two women. In 2012, Assange jumped bail and sought refuge inside the Ecuadorian Embassy, where he was beyond the reach of the authorities — but was also effectively a prisoner in the tiny diplomatic mission.

The relationship between Assange and his hosts eventually soured, and he was evicted from the embassy in April 2019. British police immediately arrested him for breaching bail in 2012, and he remains in prison. Sweden dropped the sex crimes investigations in November 2019 because so much time had elapsed.

A U.K. district court judge rejected the U.S. extradition request in 2021 on the grounds that Assange was likely to kill himself if held under harsh U.S. prison conditions. Higher courts overturned that decision after getting assurances from the U.S. about his treatment. The British government signed an extradition order in June 2022.

Meanwhile, the Australian parliament last week called for Assange to be allowed to return to his homeland.

The judges, Sharp and Jeremy Johnson, could deliver a verdict at the end of the two-day hearing on Wednesday, but they’re more likely to take several weeks to consider their decision.