Gary McKinnon began the next stage in his fight against extradition to the US to face charges of hacking US Army, Navy, Air Force and NASA computers on Tuesday.
The British hacker is facing extradition to the US on charges of hacking and causing damage to US defence sites. If found guilty he could face over $1m in fines and 60 years in jail.
When the US request for extradition was first made, McKinnon admitted that the prospect of facing court in the US "terrified him". Now he faces a hearing scheduled to last three days to see if he will remain a free man.
McKinnon was arrested in June last year on charges of computer fraud, and claims that he had illegally accessed 97 US Government computers. McKinnon told ZDNet UK in July 2005 that his actions were prompted by an interesting in the US space programme and the search for extraterrestrial life.
The US prosecution team alleges that McKinnon hacked into sensitive equipment over a one-year period from February 2001 and caused $700,000 worth of damage. McKinnon, though, denies causing serious damage.
Although McKinnon was arrested in the UK shortly after his hacking activities were first exposed, he was released under caution. Since being charged by the US authorities he has been banned from using the Internet.