WikiLeaks founder Julian Assange risked the lives of US intelligence sources named in secret documents that were leaked by his whistleblowing organisation, his extradition hearing in London heard on Monday.
After years of legal wrangling, the US government opened the case against Mr Assange, 48, and sought to portray him as an ordinary criminal rather than a free-speech champion who exposed American wrongdoing.
Mr Assange faces up to 175 years in prison over the 2010 release of hundreds of thousands of top-secret military documents and diplomatic cables on his whistle-blowing site.
The US says he worked with US army intelligence analyst Chelsea Manning to hack into a Pentagon computer and secure the files related to the wars in Iraq and Afghanistan.
James Lewis, representing the US government, said it was “one of the largest compromises of classified information in the history of the United States”.
He has been held in London’s top security Belmarsh prison since April last year after he was hauled by British police officers from Ecuador’s embassy where he had been holed up since 2012.
He sought asylum after skipping bail following his arrest in 2010 as Swedish prosecutors sought to question him over rape and sexual assault claims against two women. The case was finally dropped three months ago because of the time it had taken to bring any potential case to court.
Mr Assange had refused to go to Sweden, saying he feared being sent from there to the United States to stand trial over the WikiLeaks exposures. But he now faces the same fate if he loses the case in southeast London.
He remains a hero to many, who say his revelations helped expose the unvarnished reality of US involvement in the Middle East. Dozens of supporters of Mr Assange gathered outside the court in a noisy protest and claiming that he is being scapegoated for his involvement in embarrassing the US government.
The chanting by protesters – many holding “Free Assange” banners - prompted the judge Vanessa Baraitser to send out a note to tell them to stop interrupting the proceedings.
His father John Shipton, who was attending the hearing, told reporters: “We're all here to vigorously and firmly support Julian in this 10-year long oppression and political action.”
Mr Assange claims that he was acting as a journalist and is entitled to free speech protection enshrined in US law. Among the files published by WikiLeaks in 2007 was the video of a US helicopter attack in Baghdad that killed 11 people including two Reuters journalists.
Mr Lewis told the court that reporting was not an “excuse for criminal activities” or a licence to break ordinary criminal laws.
"What Mr Assange seeks to defend by free speech is not the publication of the classified materials, but he seeks to defend the publication of sources — the names of people who put themselves at risk to assist the US and its allies," he said.
The US Justice Department said last May that those compromised by Mr Assange "included local Afghans and Iraqis, journalists, religious leaders, human rights advocates, and political dissidents from repressive regimes".
Mr Assange has fallen out with prominent newspaper backers because of concerns that WikiLeaks published classified documents without redacting details that could endanger individuals.
Journalism organisations and civil liberties groups including Amnesty International and Reporters Without Borders say that the charges against Assange still set a chilling precedent for freedom of the press.
The hearing is not set to conclude for months and any appeal is likely to delay a final decision for years while he remains in custody.
