Gary McKinnon faces a trial in the US if his appeal is unsuccessful
Computer hacker Gary McKinnon is mounting a fresh High Court challenge to stop his extradition to the US.
Solicitor Karen Todner said papers were lodged with the High Court seeking a judicial review of the home secretary's decision not to block his transfer.
The home secretary has 14 days to respond before a judge considers it.
Mr McKinnon, 43, who has Asperger's syndrome, is accused of breaking into the US military computer system. He says he was seeking evidence of UFOs.
The computer systems he is accused of breaking into include the Pentagon.
The Glasgow-born man, now of Wood Green, north London, faces 60 years in prison if convicted.
Last month Home Secretary Alan Johnson told Mr McKinnon's family he could not block the move on medical grounds, leaving the way open for a trial in the US.
The latest legal submissions include an up to date medical report on his situation and two reports about the ability of the US prison service to deal with his circumstances.
Ms Todner 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.
She said 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.
After the 14 days in which Mr Johnson can respond, the case will then go before a single judge to be considered on paper.
A court hearing may be needed before a decision is reached on whether a judicial review will be granted.
Mr McKinnon's lawyers say he is suffering from "very severe depression" and is in danger of killing himself in preference to being extradited.
They have fought a series of long-running court battles and the latest move is expected to be his last attempt to avoid extradition.