A judge has ruled Harry Dunn’s family can bring a claim for damages against the husband of the teenage motorcyclist’s alleged killer.
Mr Dunn, 19, died in a crash near RAF Croughton in Northamptonshire in 2019.
Suspect Anne Sacoolas later returned to the US, claiming diplomatic immunity.
A Virginia court heard Mr Dunn’s family brought a claim against her husband due to a law in the US state which suggests he is liable for allowing his wife to use the car which killed the teenager.
Judge Thomas Ellis said the issue of Mr Sacoolas’s “vicarious liability” could be revisited in the future, but he denied a motion to dismiss that part of the claim at a hearing on Wednesday.
The Crown Prosecution Service has charged Mrs Sacoolas with causing the teenager’s death by dangerous driving but an extradition request was rejected by the US government in January last year.
Mr Dunn’s family have filed a civil claim for damages against Mrs Sacoolas in the US and the full case is expected to be heard in Virginia later this year.
A court hearing previously heard her work in intelligence was “especially a factor” in her departure and that she “fled” the UK for “issues of security”.
The news comes as Foreign Secretary Dominic Raab has again raised the case with the US Secretary of State Antony Blinken.
Mr Raab had already spoken to Mr Blinken in January about the case but a State Department spokesman said the decision to refuse extradition was “final”.