The lawyer for Bradley Manning, an Army private accused of passing sensitive information to the online site WikiLeaks, is seeking evidence from the government that the data allegedly leaked did not harm national security.

Manning is scheduled to appear at a military hearing in December. He was arrested in May 2010 on suspicion of carrying off one of the largest national security leaks in U.S. history.

In a pretrial submission last week , Manning’s civilian lawyer, David E. Coombs, signaled part of his potential strategy to defend the 23-year-old former intelligence analyst, who is accused of downloading information from the military’s classified computer network to be shared with Wiki­Leaks.

Manning is currently in a medium-security facility in Fort Leavenworth, Kan.

The private faces an array of charges, including aiding the enemy and violating the Espionage Act, which forbids unauthorized possession of information “related to the national defense” or transmitting such data to someone not entitled to receive it. Aiding the enemy is a potential capital offense. Prosecutors have said they would not seek Manning’s execution, though he could still face life in prison.

In Coombs’s court filing, he is seeking “damage assessments” by the Pentagon and State Department that he said concluded the information allegedly leaked represented “low-level opinions” or was “already commonly known due to previous public disclosures.”

Coombs is also seeking a video made of an incident in which Manning, while placed briefly under suicide watch at the Marine jail in Quantico, Va., was made to surrender his clothes. “The defense believes the video will support PFC Manning’s claim of unlawful pretrial punishment,” Coombs stated.

He has also requested data that he said would show “it was common for soldiers to add unauthorized computer programs” to their computers. Manning also faces charges of uploading unauthorized software to the military’s secret-level computer network.

Coombs said he had made repeated, unsuccessful requests for the information.

Successive disclosures by WikiLeaks of raw field reports from Iraq and Afghanistan and hundreds of thousands of State Department cables have angered senior U.S. government officials. Secretary of State Hillary Rodham Clinton called the disclosures “an attack on America’s foreign policy interests” responsible for “endangering innocent people.”

Coombs has identified 50 witnesses he would like to call, though it is unlikely that all will be summoned, said Jeff Paterson, a member of the Bradley Manning Support Network.

Manning will appear Dec. 16 at what is known as an Article 32 hearing, in which the Army will outline its case against him and the defense may call witnesses and cross-examine the government’s witnesses. The convening authority, an independent military officer, will decide whether to refer the case to court-martial and what the charges will be. If it proceeds to a court-martial, the case will be heard by a panel of at least five service members. The government expects the hearing at Fort Meade, Md., to last five days.