NASA hacker Gary McKinnon has had his extradition to face trial in the US delayed again.

The High Court has granted permission for a judicial review of Home Secretary Alan Johnson's decision that he can not intervene in the extradition process.

A hearing is likely in April or May 2010, and will take place against the background of a general elections campaign.

McKinnon is an Asperger's sufferer and his lawyer Karen Todner has said he is in a "very poor mental state" as a result of the "ongoing pressure of these proceedings".

Todner called on US President Obama to withdraw the application for McKinnon's extradition, and for the Home Secretary to review his decision not to intervene in the extradition.

The US accused McKinnon of breaking into US military computers, including those belonging to NASA, in a bid to prove the US government had knowledge of UFOs in 2001.

They alledge McKinnon's hacking activies caused $700,000 (£433,000) of damage and that he stole 950 passwords, deleted files at a naval base in New Jersey and rendered the military computer networks used following September 11 useless.

The British government initially approved McKinnon's extradition in 2006.

The UK authorities decided not to prosecute McKinnon, although his alleged crimes occurred in the UK because most of the evidence and witnesses are in the US.

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See also: NASA hacker McKinnon "will be treated fairly"