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Patrick Semansky, Associated Press
Army Pfc. Bradley Manning is escorted from a security vehicle to a courthouse in Fort Meade, Md., Monday, Dec. 19, 2011, for a military hearing that will determine if he should face court-martial for his alleged role in the WikiLeaks classified leaks case.

FORT MEADE, Md. — Lawyers for the Army intelligence analyst blamed for the biggest leak of U.S. secrets in the nation's history are employing a three-pronged defense. They say the troubled young private never should have had access to classified material, that his workplace security was inexplicably lax, and that the data in question caused little damage to national security anyway.

It's unclear whether any of the arguments will hold sway in a preliminary hearing that enters its fifth day Tuesday.

The case is continuing after the military released a text file purportedly discovered on a data card owned by Pfc. Bradley Manning, boldly stating the historic importance of data that would make its way to the secrets-spilling website WikiLeaks.

An Army witness said almost 500,000 classified battlefield reports were also on the card.