A High Court judge will rule on whether Home Secretary Alan Johnson was wrong to allow the extradition of computer hacker Gary McKinnon, it was announced today.
Mr McKinnon's lawyers have been granted permission for judicial review of Mr Johnson's decision that sending him to the US for trial would not breach his human rights.
His lawyer, Karen Todner, said she was "delighted" by the decision. A hearing is likely to take place in April or May.
But she warned that Mr McKinnon, who suffers from a form of autism known as Asperger's Syndrome, was in a "very poor mental state" because of stress.
She appealed to Mr Johnson to reverse his decision and asked US president Barack Obama to withdraw the request for extradition.
She said in a statement: "I am delighted that the High Court has agreed to grant permission for the judicial review of Alan Johnson's decision to extradite Gary McKinnon.
"However, that is countered by the very poor mental state of Mr McKinnon due to the ongoing pressure of these proceedings.
"I would urge Mr Johnson to review his decision and I appeal to President Obama to withdraw the application for extradition.
"Mr McKinnon's suffering has gone on long enough."
In November Mr Johnson rejected the application, saying he had "no general discretion" to refuse the request from the US government.
Authorities in the US want Mr McKinnon to stand trial for hacking into top secret military computers.
But the 43-year-old from Wood Green, north London, says he was looking for evidence of UFOs.
Mr McKinnon's mother Janis Sharp said: "I can't believe it - some common sense at last.
"This judge has made such an honourable and decent decision. The relief is incredible, indescribable.
"We've fought for so long for compassion and understanding. Gary's health has badly declined, it's been traumatic to see.
"I hope this brings him comfort that the right decision will be made, even if it requires the courts to impose it rather than our Government to reach it."