The European Court of Human Rights has refused U.K. hacker Gary McKinnon's appeal against demands for his extradition to the U.S.

McKinnon stands accused of breaking into computers belonging to NASA and the U.S. military, and had appealed against his extradition under Article 3 of the European Convention on Human Rights. He had claimed that the conditions of detention he would face if convicted in the U.S. would breach a European prohibition on inhumane or degrading treatment.

The court said Thursday it had refused his appeal, and will not prevent his extradition. The court had previously ordered that his extradition be delayed until midnight Friday while it considered his request.

It was in 2002 that a U.S. court first indicted McKinnon for the offenses, committed in 2001, although he was not arrested by U.K. police until 2005. The U.K. government first approved his extradition in 2006.

McKinnon has never visited the U.S., and the offenses of which McKinnon is accused were committed in the U.K., his lawyers Kaim Todner LLP said.

"We maintain that any prosecution of our client ought therefore to be carried out by the appropriate British authorities," the London law firm said. "U.K. citizens are at the mercy of the ever-increasing tendency of overseas prosecutors to extend their jurisdiction to crimes allegedly committed in this country."

Security consultant Graham Cluley of Sophos said the decision sent a warning to hackers.

"The message is clear -- if you hack into computers you have to realize that the legal consequences could be severe.  Others should take note of McKinnon's predicament and ask themselves: do I want to end up in his situation?" Cluley wrote.

McKinnon's lawyers said they will make one further appeal against the extradition, to the U.K. Home Secretary. The appeal will be on medical grounds, as McKinnon has recently been diagnosed as suffering from Asperger Syndrome, a neurological disorder characterized by obsessive behavior and deficiencies in social interaction.