A Harvard professor has testified at Bradley Manning's court-martial that the classified material given by him to WikiLeaks did not threaten national security in Iraq and Afghanistan.
Defence lawyers also have contended that much of the material Manning is charged with leaking had been available from public sources before the WikiLeaks disclosure.
Earlier, the US military viewed anti-secrecy website WikiLeaks as a news gathering operation.
Yochai Benkler, a Harvard University law professor and expert on media law, testified for the defence that a 2008 Defence Department report on WikiLeaks had said that a US enemy could theoretically use the site to gather information.
News24 reports that Manning had allegedly leaked more than 7,00,000 classified files, combat videos and State Department cables while serving as an intelligence analyst in Iraq in 2009 and 2010.
According to the report, the defence wanted to portray Manning as a naive but well-intentioned soldier who wanted to show Americans the reality of war in Iraq and Afghanistan.
The 21 charges against Manning include espionage, computer fraud and, most seriously, aiding the enemy by disclosing material that could be used by the al-Qaeda extremist network.
