The mother of Harry Dunn has called on the US presidential candidate Joe Biden to help bring her son's alleged killer to justice if he wins the election.
Charlotte Charles's 19-year-old son was killed when his motorbike and a car driven by American Anne Sacoolas crashed outside a US military base.
She later claimed diplomatic immunity and returned to the US, which blocked a request for her extradition.
Mrs Charles has called on Mr Biden to reverse it if he is elected.
Mrs Sacoolas, 43, was charged by the Crown Prosecution Service with causing Mr Dunn's death by dangerous driving on 27 August outside RAF Croughton in Northamptonshire.
US Secretary of State Mike Pompeo rejected an extradition request, describing the decision as "final".
In a video appeal , Mrs Charles appealed to Mr Biden to "do your best to amend" the situation - saying Mrs Sacoolas "walking free" was "tearing us apart as a family".
She said: "I please urge you, should you win on 3 November, to please reconsider the position the US has taken against us - and when I say us I don't just mean myself, I mean us as the UK as well.
"We never, ever expected to be in this position. We never thought the lady who is responsible for taking our son's life would have been able to fly home to the US and evade as best she could the UK justice system.
"All we have ever asked of the US and her, is to just allow her to face the UK justice system."