LONDON , England ( CNN ) -- The Briton accused of hacking into U.S. government computers on Friday lost his court appeal to have his case heard in Britain , his legal team said . Briton Gary McKinnon is accused of carrying out the biggest ever U.S. military hacking operation . The decision means Gary McKinnon faces extradition to the United States , where he is wanted for allegedly hacking into computers at the Pentagon and NASA . His mother , Janis Sharp , promised to appeal . McKinnon , who has admitted breaking the law and intentionally gaining unauthorized access to computer systems , wanted to be tried in Britain rather than the United States . He planned to ask judges at the High Court in London to review a recent decision by the director of public prosecutions not to pursue legal action in Britain , a spokeswoman at the prosecutor 's office told CNN July . The prosecutor 's decision effectively cleared the way for McKinnon 's extradition . The U.S. government says McKinnon carried out the biggest military computer hacking of all time , accessing 97 computers from his home in London for a year starting in March 2001 and costing the government about $ 1 million . McKinnon , currently free on bail in England , has said he was simply doing research to find out whether the U.S. government was covering up the existence of UFOs . Prosecutors in the United States and Britain disagree . `` These were not random experiments in computer hacking , but a deliberate effort to breach U.S. defense systems at a critical time which caused well-documented damage , '' Alison Saunders of the Crown Prosecution Service said in February . `` They may have been conducted from Mr. McKinnon 's home computer -- and in that sense there is a UK link -- but the target and the damage were trans-Atlantic . '' U.S. federal prosecutors accuse McKinnon of breaking into military , NASA and civilian networks and accessing computers at the Pentagon ; Fort Benning , Georgia ; Fort Meade , Maryland ; the Earle Naval Weapons Station in Colts Neck , New Jersey ; and the Johnson Space Center in Houston , Texas , among others . In one case , McKinnon allegedly crashed computers belonging to the Military District of Washington . McKinnon is believed to have acted alone , with no known connection to any terrorist organization , said Paul McNulty , the former U.S. attorney for the Eastern District of Virginia . A U.S. federal grand jury indicted McKinnon on seven counts of computer fraud and related activity . If convicted , he would face a maximum of 10 years in prison on each count and a $ 250,000 fine . McKinnon 's lawyer , Karen Todner , complained that the United States has never provided evidence to prosecutors or McKinnon 's legal team to support their extradition request -- and in fact , under Britain 's Extradition Act of 2003 , U.S. prosecutors are not required to . McKinnon has previously said it was easy for him to access the secret files . `` I did occasionally leave messages in system administrators ' machines saying , 'This is ridiculous , ' '' McKinnon has said . `` ( I left ) some political diatribes as well , but also a pointer to say , you know , this is ridiculous . '' McKinnon was on the brink of extradition in August 2008 , when the European Court of Human Rights in Strasbourg , France , refused to reconsider the decision to send him to the United States , effectively clearing the way for his transfer . Shortly after that decision , however , McKinnon was diagnosed with Asperger syndrome , and he claims that diagnosis changed the case for extradition . It was on that basis that McKinnon made his appeals in Britain . Asperger syndrome is a form of autism that affects a person 's social communication and interaction , according to Britain 's National Autistic Society . Those affected often are of above-average intelligence and have fewer problems speaking than do those with autism . They sometimes have difficulty knowing when to start or end a conversation and can be very literal in what they say , with difficulty understanding jokes , metaphors and sarcasm .
Gary also admits intentionally gaining access to government systems . Briton accused of carrying out biggest ever U.S. military computer hacking . He claims he was researching whether NASA was covering up reports of abuse .