Alleged computer hacker Gary McKinnon will not face criminal charges in the UK, the Crown Prosecution Service announced today.
Director of Public Prosecutions Keir Starmer QC announced the decision, some three months after McKinnon, 46, was saved from extradition to the U.S.
In October, Home Secretary Theresa May had decided not to extradite McKinnon to America on the basis of his health.
The CPS said today that consulting with the police and relevant authorities, they recommended to the Assistant Commissioner of the Metropolitan Police that they 'should not commence a new criminal investigation into Mr McKinnon'.
They added that the Assistant Commissioner of the Metropolitan Police 'has accepted that advice'.
Mr McKinnon, 46, from north London, would have faced up to 60 years in prison if convicted in the US.
In their statement issued this afternoon, the CPS said that in light of the logistics of prosecuting Mr McKinnon, 'the propsects of a conviction against him... were not high'.
They added: "The potential difficulties in bringing a case in England and Wales now should not be underestimated, not least the passage of time, the logistics of transferring sensitive evidence prepared for a court in the US to London for trial, the participation of US Government witnesses in the trial and the need to fully comply with the duties of disclosure imposed on the CPS."
Mr McKinnon, who suffers from Asperger's syndrome, was permitted to stay in the UK after medical reports showed he was very likely to try to kill himself if extradited.
Both Prime Minister David Cameron, who held talks on the case with US president Barack Obama, and his deputy, Nick Clegg, had condemned plans to send him to the US.
However, the decision not to extradite "disappointed" the US authorities.
Today Mr Starmer said that between February 1 2001 and March 19 2002, Mr McKinnon allegedly gained unauthorised access to 97 US Government computers.
"An investigation was launched in the US and a request for assistance was made to the National Hi-Tech Crime Unit in England and Wales.
"Following discussions between the US Department of Justice, the police and the Crown Prosecution Service in the autumn of 2002, a decision was taken that the appropriate place for Mr McKinnon to be tried was the United States."
As a result, the US sought Mr McKinnon's extradition for trial in the US.
The decision that the appropriate place for Mr McKinnon to be tried was the US was affirmed in 2009 and subsequently challenged in the High Court, and that challenge failed, Mr Starmer said.
On October 16, Home Secretary Theresa May decided not to extradite Mr McKinnon to the US. She also announced it was now for the Director of Public Prosecutions to decide whether Mr McKinnon had a case to answer in a UK court.