A British computer hacker wanted by the United States for "the biggest military hack of all time" begins a final fight today to avoid extradition.

Lawyers for Gary McKinnon, will argue in London's High Court today that he is too ill to be sent to the United States for trial because he has Asperger's syndrome, a form of autism.

McKinnon is accused of hacking the computers of the Pentagon, U.S. Army, Navy and NASA, which caused $700,000 worth of damages and shut down a network of more than 2,000 computers. If convicted McKinnon could face up to 70 years. He maintains he was searching for evidence of UFOs.

McKinnon told the BBC that he knows he committed a crime and said he was sorry for that. He disagrees with the amount of damage the U.S. says he caused and says he did not use any complex tactics.

"I'm not, you know, a master hacker," he said. "I didn't write my own programs or anything. I used commercially off-the-shelf available software."

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