A British hacker fighting extradition to the U.S. on computer hacking charges is preparing for his final U.K. appeal on Monday in London.

If Gary McKinnon loses this appeal, he would be the first British hacker extradited to the U.S. He could face up to 60 years in prison.

McKinnon, of London, is accused of deleting data and illegally accessing information on 97 U.S. military and NASA computers between February 2001 and March 2002. He's been charged in U.S. District Court for the Eastern District of Virginia.

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

The U.S. pursued extradition, which McKinnon sought to block. Then-U.K. Home Secretary John Reid approved the extradition order, but McKinnon appealed. He lost that appeal in London's High Court in April 2007.

McKinnon then filed an appeal with the House of Lords, the final court of appeal for points of law in the U.K. Five lords will hear his case on Monday and then take three weeks to decide, McKinnon said earlier this week.

If the lords reject his appeal, McKinnon said he could take his case to the European Court of Human Rights. The backlog of cases in that court, however, means that an appeal could take years and in the meantime, his extradition could proceed, McKinnon said.

McKinnon said a U.S. public defender has visited him in the U.K. to prepare for his case if he is extradited. McKinnon's passport has been taken, although he still may use a computer.

McKinnon, who said he probed the computers looking for evidence that the U.S. government has knowledge of UFOs, maintains that his hacking never caused any harm.

However, the U.S. said that the intrusions disrupted computer networks used by the military that were critical to operations conducted after the Sept. 11, 2001, terrorist attacks. The U.S. estimates the damage caused by McKinnon at $700,000.