Claim could seal Manning's fate on most serious charge if proven he knew enemy groups could obtain leaked files

The US government claims to have proof that Bradley Manning, the WikiLeaks suspect, knowingly passed state secrets to a location where it was bound to be obtained by enemy groups, a military court in Maryland has heard.

Captain Joe Morrow, a member of the five-strong prosecution team assigned to the case, said that the government would show at court martial that Manning had knowingly "aided the enemy" – the most serious of the 22 charges facing the soldier that carries the death penalty. Morrow said the evidence would show that Manning sent the information to a "very definite place" that he knew was used by the enemy.

He did not mention al-Qaida, though the terrorist network has been explicity named by the prosecution in previous hearings.

The insistence by the US government that it can prove Manning had actual knowledge that the WikiLeaks dump would be used by enemy groups was instantly disputed by the lead defence lawyer, David Coombs. He demanded that the government produce the evidence to which it was alluding.

"We haven't seen any evidence that the government has provided by discovery that supports any knowledge that the information would be obtained by the enemy," he said.

Manning has been in military jail for more than two years after he was arrested at the Forward Operating Base Hammer outside Baghdad. He is accused of being the source of the massive trove of secrets passed to WikiLeaks, and in turn published by the Guardian and other international newspapers, including Iraq and Afghanistan war logs and thousands of embassy cables.

The argument that is currently raging between the two legal sides is of supreme significance – both to Manning personally and potentially to many other parties. For Manning, 24, the legal standard that will be set in his case on the charge of "aiding the enemy" could seal his fate.

The Article 104 count carries the death penalty, though the prosecution has indicated that it will not pursue a capital sentence against Manning. That still leaves the possibility, should he be found guilty of the charge, that he will be sentenced to life in military custody with no chance of parole.

Beyond his individual future, the outcome of the debate on "aiding the enemy" has huge potential ramifications for future prosecutions involving the publication of leaks on the internet. As the American Civil Liberties Union recently pointed out, the US government is attempting to hold the soldier accountable for helping al-Qaida even though he allegedly passed information to a third party, in this case WikiLeaks.

If that standard applies, the ACLU warned, it could set a precedent in which "the threat of criminal prosecution hangs over any service member who gives an interview to a reporter, writes a letter to the editor, or posts a blog on the internet. In its zeal to throw the book at Manning, the government has so overreached that its 'success' would turn thousands of loyal soldiers into criminals."

Manning's defence lawyer, Coombs, made a similar point at the hearing. He invited the military judge, Colonel Denise Lind, to replace WikiLeaks in her mind with the New York Times.

"If I'm a government official and I'm concerned by some aspect of government practice, and I go to the New York Times with information, and the newspaper publishes it, have I now aided the enemy?" Coombs said.

The latest pre-trial hearing at Fort Meade has been attended, like all its predecessors, by Manning in person, who sat at a defence table following the courtroom discussions avidly. This week's proceedings are expected to last three days, with the judge giving her conclusions at a later date.

Earlier in the day, the rival legal teams engaged in legal argument over the manner in which the soldier allegedly downloaded hundreds of thousands of diplomatic cables from US embassies around the world. It has been alleged that he made use of the software Wget to carry out a high-speed download of the files.

The government has charged Manning with a violation of 18 USC 1030 – sometimes referred to as the computer espionage law – relating to his use of Wget. Making the case, Morrow used the analogy of a homeowner to describe how Manning, then an intelligence analyst working in Iraq, had been granted authorised access to the secure computer network SIPRnet, but had then allegedly applied to it the Wget software.

"Manning had a key to the house, but he used a bulldozer to access the information, thus exceeding his authorised access," Morrow said.

Coombs conceded that Wget was not authorised for use on the secure computers that Manning had been working on. But there were no rules in place stopping him downloading the cables; all that Wget did was increase the speed of the download.

"There were no restrictions on downloading the diplomacy database – none," Coombs said.