Lawyers acting for computer hacker Gary McKinnon today lodged papers for a fresh High Court challenge to stop him being sent for trial in the U.S.
A judge will now decide whether there is an "arguable case" that should go to a full hearing.
Gary's solicitor Karen Todner said there was new evidence showing that McKinnon was suicidal and could not survive the American prison system.
McKinnon, 43, from north London, hacked into Nasa and Pentagon computers seeking evidence for UFOs and his family fears he could face up to 60 years in a US prison.
He suffers from Asperger's syndrome, a form of autism.
His lawyers say he is also now the victim of "very severe depression" and in danger of killing himself in preference to being extradited.
They have fought a long-running series of court battles, and this is expected to be his last-ditch bid to avoid extradition.
Ms Todner arrived today at the Royal Courts of Justice in London to lodge papers for his application for judicial review.
She said there was new evidence from psychiatrists with experience of prisons - one English and the other American - to support his claim that extraditing him would violate the European Convention on Human Rights.
His removal would breach his right to life, not to be subjected to inhuman and degrading treatment and his right to private and family life, contrary to articles 2, 3 and 8 of the convention.
The legal challenge is against the latest refusal of Home Secretary Alan Johnson, made two weeks ago, not to block the extradition on medical grounds.
Ms Todner said the papers she had lodged with the courts included "an up-to-date medical report and a report from two leading authorities - one English and one American - on assurances that the American government have given in relation to Gary's treatment should he be extradited".
Both men were psychiatrists with experience in penology, the study of prison management and criminal rehabilitation.
Ms Todner said: "He could not survive the American prison system. In our view, they don't have the appropriate facilities to assist him."