The defense began its case Monday in the court-martial at Fort Meade, Md., of Manning, who has admitted leaking documents to the whistle-blowing website WikiLeaks, and filed four motions asking for a directed verdict of not guilty, maintaining the government didn't prove its case, the Los Angeles Times reported.
The judge, Army Col. Denise Lind, said she would review the briefs after the prosecution responds by Thursday.
Manning gave the anti-secrecy organization WikiLeaks more than 700,000 U.S. intelligence files, videos and diplomatic cables.
In February, he pleaded guilty to 10 lesser charges of unauthorized possession, willful communication and improper storage of classified material and could be sentenced to up to 20 years in prison.
He pleaded not guilty to violating the Espionage and the Computer Fraud and Abuse acts, which carry life sentences. He also pleaded not guilty to larceny, aiding the enemy and improper use of government equipment.
The first defense witness, Army Chief Warrant Officer Joshua Ehresman, was an intelligence analyst who supervised Manning near Baghdad. Despite working in a chaotic environment, Ehresman said Manning "was our best analyst by far. For most soldiers, you would have to spell it out. With Manning, he would come up with exactly what you were looking for. He was our go-to guy."
Also testifying was Army Sgt. David Sadtler, who said Manning showed him material describing civilians being arrested for protesting in Iraq.
"He was upset over the situation," Sadtler said.
Lauren McNamara, a friend of Manning, brought a printout of chat logs of Internet conversations between February and August 2009, just before he started providing material to WikiLeaks. Defense lawyers have said the chat logs highlight Manning's state of mind, the Times said.
"We often talked about politics, global affairs, Pvt. Manning's life before then and what his job involved," she testified. "We were just a couple of people talking about our lives, and he shared various experiences and interests. He often had interesting things to say about his job and world affairs. It seemed like he just wanted someone to talk to about these things."
Defense lawyers said they plan to call up to four dozen witnesses.