Police have handed their completed file of evidence on the death of Harry Dunn to the Crown Prosecution Service.
Northamptonshire Police confirmed they had completed the file after interviewing Anne Sacoolas in America.
Mrs Sacoolas, the wife of a US diplomat, is believed to have been driving on the wrong side of the road when her car hit Mr Dunn’s motorbike outside RAF Croughton on 27 August.
The 42-year-old cooperated with police in the aftermath of the crash but then claimed diplomatic immunity and left the UK.
Radd Seiger, spokesman for Mr Dunn’s family, said: “We are pleased that at long last Northamptonshire Police have been able to complete their investigation and hand the file over to the CPS.
“On 26 September the family were told they had less than 1% chance of somebody being held accountable for the loss of their son.”
Mr Seiger said there could have been a different outcome were it not for the “incredible determination of the most courageous and dignified family I have ever met – who have moved heaven and earth to get justice for their son”.
It was announced last week that Mrs Sacoolas would be interviewed under caution by Northamptonshire Police officers in her home country.
Mr Dunn’s mother, Charlotte Charles, previously told Sky News the family felt they were still “left in limbo”.
She also criticised the decision to fly British police to the US.
“We don’t even really understand why the police flew to see her as per her request,” she said.
Chief Constable Nick Adderley said at the time: “The suspect has cooperated fully with police and authorities and requested to be interviewed under caution in the US.
“She did not want to provide a pre-prepared statement, as is her right.”
Harry Dunn’s family are suing Mrs Sacoolas for civil damages, as well as taking legal action against the UK Foreign Office over the decision to allow her to leave the country under diplomatic immunity.
The Dunns met President Donald Trump at the White House last month to discuss the case.
Mrs Sacoolas was in the building but they turned down a surprise last-minute offer to meet her.
A source close to her previously told Sky News that she accepts she was driving on the wrong side of the road and is “terribly, terribly sorry for that tragic mistake”.
News reporter @luciabinding Police have handed their completed file of evidence on the death of Harry Dunn to the Crown Prosecution Service. Northamptonshire Police confirmed they had completed the file after interviewing Anne Sacoolas in America.