The government has opposed the participation of most of the witnesses requested by Coombs, including mental health providers and key members of Manning's brigade.
In court filings, the government argues that testimony about his mental health and the decision to deploy him are irrelevant to the case "and will only serve to distract from the relevant issues." Coombs has asked the investigating officer to compel the participation of all witnesses.
He has also requested the presence of Secretary of State Hillary Clinton and former Defense Secretary Robert Gates, who he says will affirm those opinions. Legal analysts say it unlikely either will be compelled to testify.
Nothing in the witness list or the requests for evidence appears to suggest that the defense plans to claim that Manning did not leak the material.
Eugene Fidell, a former Coast Guard attorney who teaches military justice at Yale Law School, said the testimony and the evidence "could fall in the category of extenuation and mitigation."
"In other words, something that might soften the blow, in the event that he is convicted," Fidell said. "I don't see any of that information, even on a good day, as logically suggesting an acquittal, assuming he did what the government thinks he did."
Coombs has requested a video made when Manning was detained at the Marine Corps base in Quantico, Va., in which he was ordered to surrender his clothing. He says the footage will support his claim of unlawful pretrial punishment.
The conditions of Manning's detention at Quantico — where he was held in a maximum-security, single-occupancy cell, placed on a prevention-of-injury order and allowed to wear only a suicide-proof smock at night — drew concern from Amnesty International and a request to visit from a United Nations torture investigator.
President Barack Obama and Pentagon officials have defended the conditions of his detention. Manning was moved from Quantico to Fort Leavenworth, Kan., in April.
Baltimore peace activist Max Obuszewski was one of 33 Manning supporters arrested outside the entrance to Quantico during a demonstration in March.
Obuszewski says he has "no idea what Bradley Manning did or did not do" — but if he was a source for the material published by WikiLeaks, he is "one of the people responsible for the Arab Spring."
"A lot of people in the movements for democracy have read the WikiLeaks diplomatic cables," he said.
Manning's supporters — who include, most prominently, Daniel Ellsberg, the former military analyst who released the Vietnam War records known as the Pentagon Papers — say the information he is accused of leaking was incorrectly and illegally classified. Whoever disclosed it should be protected from prosecution as a whistle-blower, they add.
Obuszewski says the Apache attack appears to be a "war crime."
"If Bradley Manning knows about war crimes, I would argue that this is information he has to release," Obuszewski said. "Whether it's classified et cetera, if you believe that there's violations of the law done by people above you in the chain of command, then you have to bring that information out."
In the video of the Apache attack, Americans can be heard laughing and calling the Iraqis "dead bastards."
The military concluded that the U.S. troops acted appropriately. It said the targets included insurgents, and the equipment carried by the Reuters employees made them difficult to distinguish from combatants.
Obama has said that Manning broke the law.
"We're a nation of laws," he told a Manning supporter in April. "We don't individually make our own decisions about how the laws operate. He broke the law."