A military hearing into the case of Bradley Manning, the soldier accused of passing American secrets to WikiLeaks, heard new details yesterday of the failure by his supervisors to note signs of emotional instability and revise his security clearance or even block his deployment.

The defence bench also highlighted the struggles suffered by Private Manning with his sexuality, suggesting he had a gender disorder, made harder to handle because the US had not yet repealed its "Don't Ask, Don't Tell" policy that forced serving homosexuals to conceal their natures.

The hearing, being held under strict security on a military base in Maryland, is expected to wind up later this week. The US military must then decide whether the case against Pte Manning for his part in last year's WikiLeaks scandal is strong enough to warrant a full court martial. If Pte Manning, who is half Welsh, were to be convicted on the most serious charges filed against him, he could spend the rest of his life in prison.

At Fort Meade, witnesses were questioned over Manning's outbursts and erratic behaviour at the base in Iraq where he served as a junior intelligence analyst in 2009 and 2010 and what action was taken. Those include overturning a table in rage and throwing a chair.

With his lawyers questioning why his access to highly sensitive intelligence was not barred after these eruptions, Pte Manning's closest supervisor, Sergeant Paul Adkins, refused to testify and cited his right against self-incrimination.

A Treasury Department Special Agent, Troy Bettencourt, who had been assigned to investigate the case, admitted that something had gone wrong in the process that allowed Pte Manning to be placed on the intelligence team with full clearance in Baghdad. "I would like to think that had I been in the chain of command, I would have maybe done things differently," he conceded.

Prosecutors revealed that after the scandal broke, they twice visited the home of an aunt of Pte Manning in Maryland where they said they found a memory card containing American secrets, allegedly stashed there by the defendant.