A British computer expert lost his appeal on Wednesday against extradition to the United States where he is accused of “the biggest military hack of all time” and could face up to 70 years in prison.

Gary McKinnon was arrested in 2002 after U.S. prosecutors charged him with illegally accessing computers, including the Pentagon, U.S. army, navy and NASA systems, and causing $700,000 worth of damage.

McKinnon told Reuters in 2006 he was just a computer nerd who wanted to find out whether aliens really existed and became obsessed with trawling large military networks for proof.

However, Britain’s highest court, the House of Lords, ruled the gravity of the charges should not be understated and they would carry a maximum life sentence under English law. It turned down his appeal against extradition.