The young Army intelligence specialist accused of leaking government secrets spent his 24th birthday in court Saturday as his lawyers argued his status as a gay soldier before the repeal of "don't ask, don't tell" played an important role in his actions.

Lawyers for Pfc. Bradley Manning began laying out a defence to show that his struggles as a gay soldier in an environment hostile to homosexuality contributed to mental and emotional problems that should have barred him from having access to sensitive material.

Manning is accused of leaking hundreds of thousands of sensitive items to the anti-secrecy group WikiLeaks, including Iraq and Afghanistan war logs, State Department cables and a classified military video of a 2007 American helicopter attack in Iraq that killed 11 men, including a Reuters news photographer and his driver.

The Obama administration says the released information has threatened valuable military and diplomatic sources and strained America's relations with other governments. Manning's lawyers counter that much of the information that was classified by the Pentagon posed no risk.

The military is conducting a hearing in a small courtroom on an Army post outside Washington to determine whether prosecutors have enough evidence to bring Manning to trial, where he could face a term of life in prison as a traitor.

Prosecutors began presenting evidence to substantiate the charges against Manning.

Army criminal investigators described evidence they collected that links Manning to the WikiLeaks website's collection of U.S. military and diplomatic secrets.

But among the first issues to arise Saturday was whether Manning's sexual orientation is relevant to the case against him.

Evidence from online chats

The basis for the charges Manning faces are transcripts of online chats with a confidant-turned-government-informant in which Manning allegedly confesses his ties to WikiLeaks and also reveals he is gay.

Maj. Matthew Kemkes, a defence lawyer, asked Special Agent Toni Graham, an army criminal investigator, whether she had talked to people who believed Manning was gay or found evidence among his belongings relating to gender-identity disorder.

Graham said such questions were irrelevant to the investigation. "We already knew before we arrived that Pfc. Manning was a homosexual," Graham said.

Prosecutors objected several times to the questions. Kemkes responded that if the government can argue that Manning intended to leak secrets, "what is going on in my client's mind is very important."

Manning's defence also sought to show that at least one item he is suspected of leaking is not classified, part of its argument that much of the information classified by the Pentagon should not have been.

Graham said she collected from Manning's belongings a DVD marked "secret" that included a video clip of the deadly helicopter attack.

But Kemkes said the video was, in fact, unclassified.

First public appearances

Manning's appearances Friday and Saturday in the Fort Meade courtroom mark the first time he has been seen in public after 19 months in detention. The Oklahoma native comes to court in Army camouflage fatigues and wearing dark-rimmed glasses. Slight and serious, he takes notes during the proceedings.

An Army appeals court on Friday rejected a defence effort to have Lt. Col. Paul Almanza as the presiding officer because of alleged bias. Separately, lawyers for WikiLeaks and founder Julian Assange are asking the military's highest appeals court to guarantee two seats in the Fort Meade courtroom.

Manning's hearing is open to the public, with limited seating.

The case has drawn an international support network of people who believe the U.S. government has gone too far in seeking to punish Manning.

More than 100 people gathered outside Fort Meade for a march in support of Manning, some holding signs declaring "Americans have the right to know. Free Bradley Manning" and "Blowing the whistle on war crimes is not a crime."

In London, several dozen protesters from gay organizations, the Occupy London protest camp and other groups rallied outside the U.S. Embassy Saturday calling for Manning's release and offering birthday wishes.