The man who leaked the "Pentagon Papers" about the Vietnam War has defended Julian Assange at his London extradition hearing.
Daniel Ellsberg says WikiLeaks acted in the public interest yet he fears Assange will not get a fair trial in the United States.
Australian-born Assange, 49, is fighting against being sent to the US, where he is charged with conspiring to hack government computers and violating an espionage law over the release of confidential cables by WikiLeaks in 2010-2011.
Ellsberg, who in 1971 leaked documents known as the Pentagon Papers to the New York Times and other papers, told the court WikiLeaks' disclosures had shown Americans how they had been misled about US action in Iraq and Afghanistan just as his leaks, which also revealed previously secret information, did about Vietnam.
Ellsberg cited a US military video, which WikiLeaks published in 2010 under the title Collateral Murder, showing a 2007 attack by Apache helicopters in Baghdad that killed a dozen people, including two Reuters news staff.
"I was acutely aware that what was depicted in that video deserved the term murder, a war crime," he told London's Old Bailey court via videolink on Wednesday.
"I was very glad that the American public was confronted with this reality of our war."
James Lewis, the lawyer representing US authorities, said Assange was not wanted for publishing the 2007 video but for disclosing a small number of documents with unredacted names of sources or informants.
Lewis said many had suffered harm or threats because they had been named.
He said some had disappeared, although he conceded there was no evidence this was directly linked to the WikiLeaks' publication.
"How can you possibly say ... that there is no evidence Mr Assange's publication of WikiLeaks put anyone in danger. That's just pure nonsense," Lewis said.
Ellsberg, who was himself charged with breaking the espionage law in a case later dismissed, said there was no evidence of physical harm or deaths because of the leaks.
The exchange with Lewis led to an outburst from Assange in the courtroom, with the judge warning him to remain silent.
Earlier, John Goetz, an investigative reporter who worked for Germany's Der Spiegel magazine on the first publication of the documents in 2010, said Assange was careful to ensure the names of informants in hundreds of thousands of leaked secret US government documents were never published.
He said the US State Department had been involved in a conference call suggesting redactions and WikiLeaks had agreed to hold back about 15,000 documents for publication.
"There was sensitivity and it was one of the things that was talked about all the time," Goetz told the court.
Assange was concerned the media should take measures "so no one would be harmed", he said.
Goetz said WikiLeaks was frustrated when a password that allowed access to the full, unredacted material was published in a book by Guardian reporters in February 2011.
Assange's lawyers argue he will not receive a fair trial in the United States and that the charges are politically motivated.
They also say he would be a suicide risk if sent to the United States, where they say he could be sentenced to 175 years in prison.
Australian Associated Press