The family of Harry Dunn, the 19-year-old motorcyclist killed outside a US airbase, have begun their court case seeking a ruling that the Foreign Office acted unlawfully in granting diplomatic immunity to the American driver of the car that killed him. Dunn was killed when his motorbike crashed into a car being driven on the wrong side of the road by Anne Sacoolas outside RAF Croughton in Northamptonshire on 27 August last year. Sacoolas, whose husband, Jonathan Sacoolas, worked as a technical assistant at the base, left the country two weeks later after the Foreign, Commonwealth & Development Office (FCDO) accepted a US claim that Sacoolas had immunity on the basis that her husband worked at RAF Croughton, a CIA listening post in Northamptonshire. Subsequent UK government efforts to seek her extradition have been rejected by the US Department of State. The claim for immunity turns on a secret agreement signed between the UK and the US that gave immunity to the staff working at RAF Croughton but only for activities in relation to their work. It was silent on the immunity status of the families of staff. The Foreign Office and the US state department interpreted the silence in the agreement as giving families full immunity. Lawyers acting for Dunn’s family claim it is a perverse interpretation of the agreement to suggest that staff members at the US base had less diplomatic immunity than their family. The FCDO argued that the silence in the secret agreement about the status of staff families was an anomaly, but nevertheless gave these family members immunity. The foreign secretary, Dominic Raab, subsequently announced that “the US waiver of immunity from criminal jurisdiction is now expressly extended to the family members of US staff” at the base, “ending the anomaly in the previous arrangements”. The Crown Prosecution Service has charged Sacoolas with death by dangerous driving, and sought her extradition. Lawyers acting for the Dunn family argue that the FCDO breached human rights law by advising Northamptonshire police that Sacoolas had immunity and then keeping key facts from the police, including her imminent departure from the UK. Sacoolas has acknowledged that she was driving on the wrong side of the road when she hit Dunn. She had only been in the UK for a few weeks when the collision happened. The two-day judicial review by remote video link is in front of Lord Justice Flaux and Justice Saini. Representing the family, Geoffrey Robertson QC said: “Since family members are not members of the mission and they have no duties, Anne Sacoolas was never entitled to any derivative or implied immunity from criminal jurisdiction.” He added that it would be “absurd” for family members to have “greater privileges and immunities” than the staff at RAF Croughton “from whom their immunity flows”. In written submissions, the FCDO’s barrister Sir James Eadie QC said: “As a matter of international and domestic law, Mrs Sacoolas automatically had diplomatic immunity as the spouse of a member of the administrative and technical staff of the US mission.” He argued the FCDO “plainly did not obstruct the police investigation”, adding: “On the contrary, the secretary of state sought to assist the police investigation, including by requesting a waiver of Mrs Sacoolas’s immunity.” Sir James told the court the US “expressly waived the immunity from the UK’s criminal jurisdiction of ‘employees’ or ‘staff members’, but that “at no point is there a waiver of the immunity enjoyed by the families of such individuals”. But Roberston argued that the FCDO “took upon itself the authority to resolve the question of immunity and ultimately and unlawfully decided to accept the US embassy’s decision that Anne Sacoolas had immunity”. He said in written submissions that the decision “obstructed the police by preventing any effective further progress in its investigation into Harry’s death and likely prosecution of Anne Sacoolas”. Robertson argued the FCDO “tacitly accepted the Sacoolas family’s departure from the UK”, referring to a text message sent to a US embassy official on 14 September 2019 – a day before Sacoolas and her family left the UK. The message read: “I think that now the decision has been taken not to waive [immunity], there’s not much mileage in us asking you to keep the family here. “It’s obviously not us approving of their departure but I think you should be able to put them on the next flight out.”