The family of Harry Dunn, the 19-year-old killed on 27 August last year after being hit by a car driven by the wife of a US intelligence officer, intends to bring a private criminal prosecution against the foreign secretary, Dominic Raab, the Guardian has learned. They claim that Raab did not have the authority to allow Anne Sacoolas to return to the United States after the incident, while there was an ongoing police investigation and while the issue of her diplomatic immunity had not been resolved. They also allege that Raab misled parliament in statements he made about Sacoolas’s return to the US. A private prosecution, brought by individuals rather than the Crown Prosecution Service or another public body, is highly unusual. The family argue that the actions of the Foreign and Commonwealth Office (FCO) amount to misconduct in public office, and perverting the course of justice. Sacoolas, who was subsequently charged with causing death by dangerous driving, returned to the US on 15 September. Earlier this month an Interpol red notice was issued for her, meaning she is “wanted internationally”. Sacoolas had moved to Britain with her family a month before Dunn was killed. Her husband, Jonathan, was working at RAF Croughton, the highly sensitive US intelligence base in Northampton. Sacoolas drove out of the base on the wrong side of the road when she hit Dunn’s motorbike – something she has never disputed. Dunn died later that night. Dunn’s parents have already applied for a judicial review of the decision to grant Sacoolas diplomatic immunity from prosecution. A deal was struck between the US and British governments in 1995 that immunity would be waived for any RAF Croughton staff charged with a criminal offence. However, an oversight led to no mention being made of dependants. The US government has argued that under the Vienna Convention, Sacoolas still qualifies for diplomatic immunity, and in its public statements the British government has accepted this. On 18 June, the High Court in London will determine whether or not to order the FCO to disclose the rest of the documents relating to Sacoolas’s departure, and then set a date for the judicial review. Raab claims the FCO did not know Sacoolas had left the country until it was informed by the US embassy a day later, on 16 September. In a statement to parliament on 21 October 2019, he said: “On 13 September, the FCO was informed by the US Embassy that they would not waive immunity, and that the individual would be leaving the country imminently, unless the UK had strong objections. We duly and immediately objected in clear and strong terms and have done since.” Following disclosure of FCO documents connected to the judicial review, the family discovered a text from senior diplomat Neil Holland, then serving as the FCO’s director of protocol, to his US embassy counterpart, stating: “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 feel able to put them on the next flight out …” The text was dated 14 September, a day before Sacoolas left. Dunn’s parents argue that this text directly contradicts the account Raab gave to parliament, of “clear and strong” FCO opposition to her immunity and departure. Charlotte Charles, the mother of Harry Dunn, told the Guardian the family were distraught when they read this. “How could Dominic Raab have told parliament that he and the Foreign Office objected in clear and strong terms, when the FCO told the Embassy it was fine and dandy to put them on the next plane? He misled parliament and he lied to us. He must resign or be sacked by Boris Johnson. He is lying over what he knew about the death of our boy to cover his back, and that is too upsetting to put into words. “We have worked so hard to avoid any dispute and gave him every chance to do the right thing. Dominic Raab must face the consequences himself through the criminal courts. We didn’t want any of this – it’s our last resort. But unlawful actions followed by a cover up must have consequences.” Dunn’s parents believe Raab also misled them about how and when he became involved in the case. They say he told them in private meetings that he had asked the US embassy to waive Sacoolas’s immunity on 5 September. But last week, in response to questions from ITV News, the Foreign Office stated that Raab had not known about Dunn’s death until after 12 September. Tim Dunn, Harry’s father, told the Guardian: “I’ve never trusted Dominic Raab from the moment I first met him, on 9 October. He told us in that meeting that he had asked for immunity to be waived on 5 September. Now the FCO is telling the nation that he didn’t know about Harry then! Both versions can’t be true.” In a wide-ranging interview with the Guardian’s Weekend magazine to be published on Saturday, the family said they had lost faith in the government. Niall Dunn, Harry’s twin brother, wrote to Johnson last month, saying: “Please get involved in our case. Anyone can see that the Foreign Office has made a mess of this.” He has yet to receive a response. Radd Seiger, adviser and spokesperson for the family, said: “The UK government unilaterally allowed Anne Sacoolas to leave the country when they had no power or authority to do so. Not only did they let her go, they kept the very organisation whose job it was to establish whether her claim to diplomatic immunity was valid, Northamptonshire police, in the dark for 14 days about the ambiguity surrounding the claim. They didn’t let them know she had gone until the day after she left. “Harry Dunn’s parents are now clear that these actions constitute misconduct in public office. The FCO told Northants olice on 2 September that Anne Sacoolas had diplomatic immunity, presenting that as a fact, effectively bringing the investigation to a halt. That would appear to be interfering in a lawful investigation by a police force, or perverting the course of justice. These crimes, if proven, are amongst the most serious on our country’s statute books.” An FCO spokesperson said: “We have the deepest sympathy for Harry’s family. No family should have to experience what they have gone through. The case remains of the highest priority for the foreign secretary, who continues to raise it with the US government, including earlier this month. “Both the foreign secretary and the prime minister have been clear with the US that the refusal to extradite Anne Sacoolas amounts to a denial of justice, and that she should return to the UK. The foreign secretary remains ready to meet Harry’s family and to support them to get the justice they deserve.” The FCO says it is confident that it has acted properly and lawfully in relation to the death of Harry Dunn.