The testimony came during a pre-trial hearing at Fort Meade, Md., to determine if Pfc. Bradley Manning will face a court-martial on charges he leaked classified documents to the whistler-blowing Web site, among other things. The preliminary military hearing continues Tuesday.
In Monday's session, a cybercrimes investigator testified more than 100,000 U.S. State Department cables were found on a secondary computer used by Manning. Special Agent David Shaver of the Army's Criminal Investigation Command said investigators also found software that allows a user to copy data to a writable CD.
Manning faces 22 charges, including aiding the enemy, after being accused of distributing hundreds of thousands of secret government documents to WikiLeaks, which posted them online. He is accused of stealing and leaking State and Defense department classified information while he was an intelligence analyst in Iraq in 2009 and 2010.
Prosecution witnesses also testified about a May 2010 e-mail sent to an acquaintance that Manning apparently thought he had encrypted which said, "I was the source of the 12 July 07 video from the Apache weapons team which killed two journalists and injured two kids," The Washington Post reported.
Prosecutors also presented evidence of computer chat logs between Manning and WikiLeaks co-founder Julian Assange discussing the exchange of government information.
Experts told the Post the testimony so far has been damaging to the defense.
"You add it up, add it up, and eventually it gives people something approaching a moral certainty" that Manning committed the crimes, said Eugene Fidell, a visiting lecturer in military justice at Yale Law School.