An Army investigator has said he found more than 10,000 State Department cables and other classified material on a computer used by an intelligence analyst charged with giving those secrets to WikiLeaks.
In the most damaging testimony so far at the pretrial hearing at Fort Meade, Maryland, Special Agent David Shaver said the files were linked to the user profile of the defendant, Pfc Bradley Manning.
Mr Shaver said he also found assessments of Guantanamo Bay detainees and several versions of a 2007 helicopter attack video that WikiLeaks posted. Manning's lawyer will cross-examine Mr Shaver when the hearing resumes on Monday.
Mr Shaver told the military hearing he discovered evidence that someone had used the computer to streamline the downloading of the cables with the apparent aim of "moving them out".
It was the US government's first hard evidence linking Manning with the wealth of confidential government information that showed up on WikiLeaks - battlefield reports from Iraq and Afghanistan, diplomatic communications, a military video showing a US helicopter attack that killed 11 men, and more.
Mr Shaver's appearance capped the third day of a hearing that will determine whether Manning will be court-martialled on 22 charges, including aiding the enemy. The testimony was potentially the most damaging so far.
Mr Shaver said the material he found at the intelligence analyst's work station in Iraq was all linked to the username bradley.manning or Manning's user profile. He said he examined two computers that were assigned to Manning while he was working in Baghdad in 2009 and 2010. The other machine, he said, contained evidence that someone had conducted more than 100 searches using the keywords "WikiLeaks" and "Julian Assange", the organisation's leader.
Those terms seemed "out of place" on a computer that was used for analysing intelligence about Iraq, said Mr Shaver.
Manning's lawyers have neither acknowledged nor denied that the intelligence analyst was behind the leaks. Instead, they have pressed the government to explain why Manning remained entrusted with access to highly sensitive information after showing hostile behaviour to those around him.
Manning, 24, could face life in prison if convicted.