FORT MEADE, Maryland (AFP) - Prosecutors called an officer from Bradley Manning's unit to the stand Sunday on the third day of a hearing to decide whether the US Army private should face a court-martial for allegedly spilling secrets to WikiLeaks. Manning, who spent his 24th birthday in court on Saturday, is potentially facing life in prison in connection with what has been called one of the most serious intelligence breaches in US history. Manning is accused of downloading 260,000 US diplomatic cables, videos of US air strikes and US military reports from Afghanistan and Iraq from classified computer networks while serving as a low-ranking intelligence analyst in Iraq and providing them to WikiLeaks. The first witness on Sunday was Captain Casey Fulton, a military intelligence officer with the 10th Mountain Division who served with Manning in Iraq. US Army prosecutors began their questioning of Fulton with general queries about the training an intelligence analyst receives, what their responsibilities are and the safeguarding of classified or secret information. The pre-trial hearing which opened Friday at this sprawling army base near Washington is to decide whether Manning should face a court-martial - a recommendation made by the presiding officer, US Army Lieutenant Colonel Paul Almanza. It is expected to last up to a week with more than a dozen witnesses being called by prosecutors and Manning's defense team, which is made up of a civilian attorney and two military-appointed lawyers. Almanza is not expected to make his recommendation until several weeks after the conclusion of the hearing, which is being attended by several dozen members of the public and media from around the world. During Saturday's testimony, Manning's attorneys said the soldier struggled with gender issues and emotional problems while deployed near Baghdad between November 2009 and May 2010, when he was arrested. In cross-examination of US Army investigators and one of Manning's former superior officers, the defense team sought to establish he was suffering from mental health problems and that his commanders failed to take action or revoke his security clearance. Manning's civilian attorney, David Coombs, brought up emails Manning sent in April 2010 to the senior non-commissioned officer in his unit in Iraq in which he included a picture of himself dressed as a woman and said that his troubles were "impacting his ability to do his job." The defense also sought to establish that security was lax at Manning's unit in Iraq and that the material published by WikiLeaks did not do serious damage to US national security.