British hacker Gary McKinnon, an Asperger's sufferer who broke into US military computers, will not be extradited to the United States following a 10-year legal fight, Britain said on Tuesday.
"Mr McKinnon is accused of serious crimes, but there is also no doubt that he is seriously ill," interior minister Theresa May told parliament.
She said extradition would breach McKinnon's human rights by posing a high risk that he might attempt to commit suicide.
McKinnon, 46, was arrested in London in 2002 for breaking into dozens of Pentagon and NASA computers, leaving 300 machines at a naval air station immobilised just after the terrorist attacks on September 11, 2001.
He has never denied the hacking, claiming he was looking for classified US documents on UFOs.
His supporters said he could have faced up to 60 years in a US jail for the breaches, which the US says caused USD 800,000 worth of damage.
The hacker, who has become a symbol of the campaign to revamp Britain's extradition deal with the United States, lost appeals in Britain's House of Lords and the European Court of Human Rights during his decade-long fight.
He was diagnosed with Asperger's, a form of autism, in 2007, after an autism expert watched him in a television interview and contacted McKinnon's lawyer.