A British hacker who admitted breaking into U.S. military computers hoping to uncover evidence of UFOs looks set to be extradited to the U.S. after the highest British court dismissed his appeal against the extradition on Wednesday.

Gary McKinnon, of London, will be the first person to be extradited to the U.S. for computer-related crimes. He could face up to 60 years in prison.

McKinnon, aged 42, said he plans to appeal the decision to the European Court of Human Rights, the last appeal he can file, according to his attorney, Karen Todner. That appeal will be lodged today in Strasbourg, France, she said.

"He's devastated and so is his family," Todner said.

McKinnon will also request that his extradition be delayed until his last appeal can be heard, Todner said. He has 14 days to file that request. If it is denied, McKinnon would be extradited to the U.S. while his European appeal proceeds, Todner said.

The European Court of Justice has a "massive backlog" of cases, and it could take up to two years for the appeal to be heard, Todner said.

In his appeal before the Lords, McKinnon argued that when U.S. prosecutors offered him a shorter sentence in return for a guilty plea, that offer put disproportionate pressure on him to surrender his legal rights and particularly his right to contest extradition¨. Pressure of that kind, he argued, runs counter to English law.

But in their judgement, the Lords of Appeal said "The difference between the American system and our own is not perhaps as stark so stark as the appellant's argument suggests. In this country too, there is a clearly recognized discount for a plea of guilty."

U.S. prosecutors had said that in return for pleading guilty to two counts of fraud and related activity in connection with computers, McKinnon could be sentenced to as little as three years in prison, of which he would likely serve only 6 to 12 months in a U.S. prison before returning to the U.K. to serve the rest of the sentence.

An equivalent offense committed against a target in the U.K. could have got him life imprisonment, the Lords of Appeal said. "The gravity of the offenses alleged against the appellant should not be understated."

McKinnon had admitted to using a program called "RemotelyAnywhere" to hack into PCs in the U.S. late at night when employees were gone. His hacking exploits started to unravel after McKinnon miscalculated the time difference between the U.S. and the U.K., and one employee noticed a PC acting oddly.