Washington (CNN) -- The attorney for Army Pfc. Bradley Manning, the accused WikiLeaks leaker, says he doesn't have any information indicating that Manning leaked tens of thousands of pages of documents on the Afghanistan war to the WikiLeaks website.
"I have not talked to my client about that. I have not seen anything, nor have I heard anything that would definitively tie him to that," said attorney David Coombs in an exclusive interview with CNN.
Manning has not been charged with leaking those Afghanistan field reports, but U.S. military officials have told CNN that he is the prime suspect in that leak. "There's nothing that I have seen that indicates that there's any evidence tying him to any of these leaks," said Coombs.
Manning, an Army intelligence analyst, is being held in solitary confinement at a Quantico, Virginia, detention facility. He is charged with leaking an airstrike video that the whistleblower website WikiLeaks published in April.
Manning, 22, has been charged with illegally transferring classified data onto his personal computer and adding unauthorized software to a classified computer system in connection with the leaking of a video of a helicopter attack in Iraq in 2007.
He has also been charged with communicating, transmitting and delivering national defense information to an unauthorized source and disclosing classified information concerning the national defense with reason to believe that the information could cause injury to the United States. Those charges are in connection to the leak of the same video.
Coombs said he does not yet know how Manning will plead to the charges.
The government is being tough in its handling of the charges related to the video, Coombs said.
"They're listing it as several separate charges, which could carry a maximum of 52 years," he said.
His client has invoked the Fifth Amendment and is refusing to answer questions from investigators. Manning will be examined by a board of three mental-health experts who will conduct a battery of tests to see whether he suffers from any mental problems and whether he was suffering from them at the time of the alleged leaks.
The military will then decide whether Manning should be court-martialed, Coombs said.
The 2007 footage shows an Apache helicopter gunship attack that killed a dozen Iraqi civilians, including two journalists from the Reuters news service.
The footage made its way onto the WikiLeaks website. "This tragic incident was investigated at that time by the brigade involved and the investigation found that the forces involved were not aware of the presence of the two reporters, and that all evidence available supported the conclusion by those forces that they were engaging armed insurgents, and not civilians," Maj. Shawn Turner, a U.S. military spokesman, told CNN in a previous written statement.
Coombs said Manning's military unit knew of mental problems he was having before the time of the leaks. This occurred during Manning's deployment to Iraq, according to Coombs.
"The unit has in fact documented a history, if you will, from as early as December of 2009 to May of 2010 of behavior that they were concerned about." When asked what that behavior was, Coombs said, "Well, I've only seen very limited documentation of the mental concern by the unit. But his immediate supervisor did document prolonged periods of disassociated behavior, quite a bit of nonresponsiveness from Pfc. Manning. And, again, that progressed from the very beginning of the deployment and deteriorated somewhat toward the end."
Officials from Manning's unit were so concerned that they disabled Manning's weapon, Coombs said. But aside from that and sending him to a chaplain, Coombs said, the unit did virtually nothing to help him.
Manning served with the 2nd Brigade of the 10th Mountain Division. He had top-secret clearance as an intelligence analyst with the Army while he was stationed in Iraq.
An official from the military office that deals with the media regarding the WikiLeaks story did not respond to CNN's calls and e-mail.
Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said in July he was outraged and appalled by the document leak and said both WikiLeaks and its source "might already have on their hands the blood of some young soldier or that of an Afghan family."
Coombs said the leaked information didn't reveal anything new. He acknowledged that the leaks named Afghans who were cooperating with U.S. forces in the war, but said because the names were spelled phonetically, insurgents likely couldn't track them down and the information would not be of much use to insurgents. Coombs said the comments from Mullen and Defense Secretary Robert Gates would hurt his client's chances to get a fair trial.
Julian Assange, WikiLeaks founder, has declined to say where his whistleblower website got about 91,000 U.S. documents about the war. About 76,000 of them were posted on the site on July 25 in what has been called the biggest leak since the Pentagon Papers about the Vietnam War. The documents deal with information on the hunt for Osama bin Laden, attacks on U.S. troops and their responses, relations between Americans in the field and their Afghan allies, intramural squabbles among Afghan civilians and security forces and concerns about neighboring Pakistan's ties to the Taliban.
Coombs said that Manning has been in solitary confinement since being brought to Quantico.
"Obviously, being in solitary confinement is very difficult," Coombs said. "But the individuals at the confinement facility are very professional. They're doing a very good job. And he's aware of all the people who are rallying to his support. So his spirits are relatively good. In addition, he is being treated now by a forensic psychiatrist. And he is responding positively to that treatment."
Coombs told CNN that Manning is being given medication for depression and sleeplessness.
CNN's Carol Cratty and Dugald McConnell contributed to this report.
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