Hacker Gary McKinnon interviewed in 2006
Prime Minister Gordon Brown has been urged to halt the extradition to the US of computer hacker Gary McKinnon.
Mr McKinnon, from Wood Green, north London, faces up to 70 years in prison if found guilty in the US of breaking into military computers.
Supporters held a vigil and delivered a letter to Downing Street calling for him to be tried in the UK instead.
Campaigners said the fact that Mr McKinnon has Asperger's Syndrome should be taken into account.
Glasgow-born Mr McKinnon trespassed on networks owned by Nasa, the US Army, Navy, Air Force, and Department of Defense in 2001 and 2002.
Despite taking his appeal to the House of Lords last year, he lost a six-year legal battle to avoid extradition.
The European Court of Human Rights also declined to back Mr McKinnon's case against extradition.
A decision on his proposed extradition is expected at a High Court hearing on 20 January.
Supporters held a candlelit protest outside the US Embassy on Friday.
Mr McKinnon's mother Janis Sharp said: "Gary is terrified, he's in pieces. The whole situation is heartbreaking, it's gone on for so long."
She added: "I think the US was embarrassed because Gary came out and said there were no passwords and no firewalls."
The US military said that Mr McKinnon left 300 computers at a US Navy weapons station unusable immediately after the 11 September 2001 attacks.
Mr McKinnon claims he was looking for UFO files.
Nadine Stavonina-de Montagnac, co-founder of the Autistic Culture Movement and Free Gary campaign spokeswoman, said this kind of obsessive behaviour was characteristic of people with Asperger's.
She said: "His obsession was so strong, he couldn't fight it. Even now Gary doesn't know what he's done wrong."
She added: "He is such a vulnerable man and I'm relying on Gordon Brown to help him."