A US military judge on Wednesday ruled that Bradley Manning's motive for allegedly leaking a cache of secret government files to WikiLeaks is no defense against the charges he faces.
Manning, an army private who was arrested in May 2010 while serving as an intelligence analyst in Iraq, faces trial in June for passing diplomatic cables and war logs to the anti-secrecy website run by Julian Assange.
Manning's lawyers had argued evidence regarding the soldier's motivation for illicitly passing the confidential documents to WikiLeaks should be heard at trial, but judge Denise Lind largely threw out the request.
In what amounts to a boost for the government, Lind said Manning's motive was not a valid defense.
Much of the ruling, given at the latest pre-trial hearing at Fort Meade military base in Maryland, was inaudible because of technical difficulties with the live television link to the courtroom.
But a US Army legal advisor told reporters afterwards any evidence regarding Manning's reasons for orchestrating the leak could only be heard if it was to argue that the soldier did not "knowingly aid the enemy," chiefly Al-Qaeda, by uploading and then releasing the files.
"In those circumstances evidence can be presented, but otherwise, motive is not relevant, unless the government opens the door in some other way," the advisor said of the judge's ruling.
WikiLeaks caused deep embarrassment in Washington and enraged US allies by publishing the secret files on the Internet in a series of massive "data dumps" that became the biggest security breach in American history.
Advocates of government transparency say the cables and war logs shed light on US action abroad, but opponents of the disclosures say they endangered diplomats and their sources and were a gift to America's enemies.
Manning's trial has been put back several times but is currently scheduled to start on June 3.
The 25-year-old faces life imprisonment if he is convicted of the most serious charge that he "aided the enemy," that is if he acted in the knowledge the information could eventually be accessed by Al-Qaeda and its affiliates.
Manning has been in custody since his arrest in Iraq, most notably being held at a US Marine Corps jail in Quantico, Virginia, in harsh conditions that judge Lind had earlier ruled as "excessive" and at times illegal.
Any sentence Manning eventually receives will be reduced by 112 days because of his treatment at Quantico, where he was held for nine months until being moved in April 2011 to a US Army prison at Fort Leavenworth, Kansas.
At Wednesday's hearing the prosecution sought to refute a defense motion that Manning's case should be dismissed because he was denied his constitutional right to a speedy trial.
Major Ashden Fein said the government has "continually worked" the case and exceeded the "reasonable diligence" standard required despite the complex nature of the charges against Manning and the mass of documents involved.
The accused's civilian defense lawyer, David Coombs, however, countered that the proceedings had moved at "a snail's pace."
Manning's supporters held placards outside Fort Meade before the hearing commenced, one of which read: "964 days jailed without trial."