Nasa hacker Gary McKinnon has been granted a High Court review of the home secretary's decision not to step in to halt his extradition to the US.
Karen Todner, McKinnon's solicitor, said in a statement on Wednesday that she was "delighted that the High Court has agreed to grant permission for the judicial review".
Mr Justice Mitting, considering whether to grant the review, said McKinnon's application raised two issues. First, whether the home secretary was compelled by the medical evidence to refuse to surrender McKinnon to the US due to human-rights considerations; and second, whether the medical evidence of Professor Turk, who did a fresh psychiatric evaluation of McKinnon, constitutes a change in circumstances.
The judge said that if the answers to both issues were affirmative, then it is arguable that the home secretary's decision to extradite Mr McKinnon would be unlawful.
Todner called on home secretary Alan Johnson to review his decision, and urged US president Barack Obama to withdraw the US application for extradition. She added that the likely date of the review would be in April or May.
McKinnon's legal team put in the application for a judicial review in December. At the time, the team submitted fresh psychiatric evaluations of McKinnon's mental state, plus commentary on assurances received from the US that McKinnon would receive an appropriate level of care in the US.
McKinnon, who has Asperger's syndrome, is suicidal and on medication, according to his legal team. The self-confessed hacker will remain in the UK pending the judicial review, said Todner.
US authorities allege that McKinnon hacked into 97 US military systems between 2001 and 2002, causing $700,000 (£430,000) damage. McKinnon admits the hacks, claiming he was looking for evidence of extraterrestrials, but denies causing any appreciable level of damage.
McKinnon lost a High Court judicial review concerning Johnson's decision in July. However, since then his legal team has gathered fresh evidence of his psychiatric condition.