While Sacoolas was named in British media reports and by the United Kingdom prime minister as the suspect driving the vehicle that allegedly involved in the collision with Dunn's motorcycle, the US State Department declined to confirm her or her husband's identity.
Ms Sacoolas is believed to have been driving on the wrong side of the road.
"British Prime Minister Boris Johnson added Monday that he also hopes Sacoolas will go back to England and face the consequences, noting that he would be "raising it" with the White House" if the situation can't be resolved.
'All we need to do is ask her to come back, ' said Mrs Charles, 44.
Diplomatic immunity is an worldwide agreement that exempts diplomats and their families from prosecution in host countries.
Foreign Secretary Dominic Raab has been urging U.S. ambassador Woody Johnson and Secretary of State Mike Pompeo to reconsider their protection for Mrs Sacoolas.
Radd Seiger, a spokesman for Mr Dunn's family, said British authorities had asked their USA counterparts for immunity to be waived "several times".
Referring to the diplomat's wife, Mr Adderley said: "During the initial investigation we were given some assurances by the American authorities that she would co-operate fully with the police and. that she would not be leaving the community, and would not be leaving the country, and then the next minute we found out that, actually, she and her family had left. The U.S. Embassy has been and will continue to be in close contact with appropriate British officials". "The larger goal of keeping diplomacy open and trusting when we send diplomats and their families elsewhere is that they will be free from detention from another country".
The collision between a Volvo and a motorbike saw 19-year-old Mr Dunn lose his life. We're broken", the family said."We can't grieve.
British Prime Minister Boris Johnson urged the U.S. Embassy on Monday to re-think using immunity to protect Sacoolas.
The death sparked widespread outrage after authorities revealed that Sacoolas claimed diplomatic immunity under global law, allowing her to avoid prosecution and leaving British authorities and Dunn's loved ones to demand that she return to face the consequences of her actions. This means that they can avoid arrest for nearly any crime in another country, although the home country is allowed to waive immunity, WaPo reported.
The teeanger, who had clocked up 50,000 miles on motorcycles, suffered horrific injuries and died in hospital.
Using diplomatic immunity Sacoolas was able to subsequently able to leave the country, despite having accepted liability for the crash at the scene, reports the Daily Telegraph.
"Try and make our voice even more heard there", Tim Dunn said.
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