The pre-trial hearing of Bradley Manning, the gay US soldier accused of sending many sensitive documents to the Wikileaks website, was told by his defence lawyer that he struggled with gender identity issues.

Manning’s case is currently being appraised to see whether the military has sufficient evidence to send him to a court-marshal.

The gay soldier was working as a military intelligence specialist when he was arrested in May 2010 in Iraq on suspicion of passing restricted material to the whistleblower website and has been charged with offences including making information available to the enemy.

One witness has said Manning, who turned 24 on Saturday, showed a picture of himself wearing women’s clothing to a superior, and said he was struggling with his gender identity.

Captain Steven Lim, an intelligence officer and witness at the pre-trial hearing, said he sent the picture in an email to Master Sergeant Paul Adkins, but that Adkins did not act on the email until after Manning’s arrest.

A second witness told the hearing Manning had a Facebook page for his female alter ego, Breanna.

Sergeant 1st Class Troy Bettencourt added that Manning had been sent to Iraq despite being “unstable” because the armed forces were short of intelligence analysts.

In records of a conversation released this summer, the gay soldier told a rights campaigner he had been assaulted and mocked in the army because of his sexuality.

Unable to come out because of the Don’t Ask, Don’t Tell policy, Manning reportedly said: “It took them a while, but they started figuring me out, making fun of me, mocking me, harassing me, heating up with one or two physical attacks.”

When prosecutors objected to the line of questioning, defence lawyers argued it was necessary to build a picture of Manning’s mindset at the time of the alleged leaks.

It is believed that Manning’s lawyers are cataloguing perceived failures of the US Army in a bid to mitigate the severity of any sentence eventually handed down to Manning.

The hearing continues today in Maryland.