The 19-year-old was killed when a car being driven on the wrong side of the road crashed into his motorbike outside RAF Croughton in Northamptonshire in August 2019.
Sacoolas, whose husband Jonathan Sacoolas worked as a technical assistant at the base, left the country a few weeks later after the US asserted she was entitled to diplomatic immunity.
But why was she able to leave the country
Here, we look at why the civil case was brought and what we have learned from the damages claim.
Why did Anne Sacoolas get diplomatic immunity?
The US Government and the Foreign, Commonwealth and Development Office’s (FCDO) position is that diplomats and their dependents (such as spouses or children) cannot be arrested or prosecuted for any crime, or civil case.
This immunity also applied to US administrative and technical staff at RAF Croughton in Northamptonshire, meaning Sacoolas had diplomatic immunity at the time of the crash.
Following the crash Sacoolas was questioned by police but not arrested. Three weeks later she returned to America on a US Air Force plane.
Why was a damages claim filed in the US and not the UK?
After Sacoolas returned to the US, an extradition request was submitted by the Home Office but that was rejected by the US State Department in January 2020.
The Dunn family were advised that, although there could be no criminal proceedings in the US, since the incident took place in the UK, they could bring a civil claim for damages against Sacoolas as her immunity was no longer valid when she returned to her home country.
What had happened in the civil case before it was resolved?
Lawyers acting on behalf of Anne and Jonathan Sacoolas had attempted to throw the case out on the grounds it should be heard in the UK, despite admitting she would not agree to face trial due to a “concern” she would not “receive fair treatment”.
Judge Thomas Ellis dismissed Sacoolas’s submissions that the UK was a “more convenient” forum, keeping the case in Virginia – describing the motion as “not warranted”.
Mr Dunn's parents, Charlotte Charles and Tim Dunn, then flew out to the US to give evidence under oath as part of the “discovery” process.
What did the judge have to say about the case?
In his judgment which threw out Sacoolas’s motion to dismiss the claim, Judge Ellis said: “While it is commendable that defendant Anne Sacoolas admits that she was negligent and that her negligence caused Harry Dunn’s death, this does not equate acceptance of responsibility.
“Full acceptance of responsibility entails facing those harmed by her negligence and taking responsibility for her acts where they occurred, in the United Kingdom.”
What would have happened if the case had not been resolved?
Anne Sacoolas and her husband Jonathan would have had to have gone through a process known as a “deposition” in which they would have been compelled to give evidence under oath.
If the case had not been resolved by the end of the depositions, a trial would have taken place in the civil courts in Virginia where a panel of jurors would have determined what financial settlement, if any, the Dunn family would be entitled to.
What new information has come to light through the civil claim?
The civil case has unearthed a great deal of previously unheard material, such as the State Department roles held by the Sacoolases at the time of the crash.
The Alexandria District Court in the US State of Virginia heard the pair’s work in intelligence was a “factor” in their departure from the UK – with the couple leaving for “security reasons”.
The court heard Sacoolas had not returned to the UK due to a “fear” that because of the “media attention, she would not have a fair trial”.
Her lawyer John McGavin said she was “currently apologetic” and “accepted responsibility for the accident”.
Does a resolution in the civil case mean the Dunn family’s campaign has ended?
The Dunn family’s main objective was for Anne Sacoolas to face a criminal charge through the UK justice system.
Foreign Secretary Liz Truss has vowed to continue the fight to get Sacoolas to return to the UK to face "justice" over the death of Mr Dunn.
Speaking in the US where she will meet with US President Joe Biden as part of a trip to Washington for the UN General Assembly, Ms Truss was asked if the resolution of a civil case in the UK was the end of the road for the British effort for Sacoolas's return.
"Absolutely not. We continue to press for justice for Harry," she said.
She added she had raised the case of Harry Dunn with US Secretary of State Antony Blinken and would take a "hard headed" approach on the world stage.
"I've also spoken with Harry Dunn's mother and I've raised that issue with the US Secretary of State as well," she said.
"Harry must get the justice he deserves."