Self-confessed British hacker Gary McKinnon, who is fighting extradition to the US, broke into more than 73,000 US government computers, including those of the US Army, Navy and Nasa, and deleted critical data, the House of Lords heard today.
The charges emerged at McKinnon's appeal against extradition, heard by five British Law Lords in parliament this morning.
Papers before the Lords showed that investigators traced the breaches to McKinnon's computer, which was seized by British police. McKinnon admitted responsibility in an interview under caution.
McKinnon told Computer Weekly last week that he started hacking in 1999, looking for evidence of extraterrestrial beings and technology, which he believed the US government was hiding.
Police from the former National Hi-Tech Crime Unit arrested McKinnon in 2002.
McKinnon's appeal is based on his contention that the terms of a plea bargain offered to him by US prosecutors were coercive and put "unconscionable pressure" on him to give up his right to an extradition hearing.
The terms offered a choice of "coming quietly" or "having the book thrown at him", said Edward Fitzgerald, acting for Liberty, the human rights watchdog.
The terms were to volunteer to appear and plead guilty in a US court. In return, the prosecution would ask that McKinnon serve between 37 and 46 months in a low-security prison. The would offer him repatriation to the UK after 18 months, and probable release under license after serving half his sentence.
If he did not waive his rights, the US would press for a sentence of at least eight to 10 years in a high-security prison, with no repatriation.
David Pannick QC told the lords the offer was made in a letter from Ed Gibson, then special attaché to the embassy in London and currently special legal adviser to Microsoft in the UK, on behalf of the US Attorneys Office.
In questions to counsel, the Lords were concerned whether Gibson's offer was merely setting out "the facts of life" as Baroness Hale, put it, or whether the prosecutors exaggerated their influence over repatriation procedures, as these are handled by a different section in the US justice department.
The Lords will hear arguments for the US government later this afternoon. They are expected to take two weeks to deliver their judgement.
The case continues.
More on Gary McKinnon's case >>
Photograph by Ian Grant