The hearing is to determine if there is enough evidence to court-martial Pfc. Bradley Manning, who could face the death penalty for allegedly turning over information to the WikiLeaks Web site, The Washington Post reported Monday.
In testimony Sunday, witnesses discussed issues with computer security at Forward Operating Base Hammer in Iraq.
Defense attorneys also said military superiors should have noticed troubling behavior and revoked Manning's security clearance before WikiLeaks received any material.
The newspaper said witnesses testified Manning was violent and withdrawn at different points. He also allegedly told a superior he struggled with gender identity.
Manning is accused of releasing diplomatic cables, classified U.S. military reports and video of a 2007 U.S. helicopter attack on Baghdad to the WikiLeaks Web site.