The State Department has refused to extradite Anne Sacoolas.

The family of Harry Dunn, a British 19-year-old who died last year after his motorcycle was struck by the vehicle of an America diplomat’s wife, filed a wrongful death lawsuit on Wednesday.

Radd Seiger, an adviser for Dunn’s parents, said in a statement that they filed the suit in U.S. District Court in Virginia because Anne Sacoolas has spent more than a year avoiding prosecution for allegedly striking Dunn while driving the wrong way in her SUV on Aug. 27, 2019.

Sacoolas initially cooperated with investigators before she and her husband, also named in the lawsuit, fled to the U.S. about three weeks after the incident. They claimed diplomatic immunity, and, in January, the State Department denied an extradition request.

“You do not get to kill someone and walk away in a rules-based society,” Seiger said in the statement.

Representatives for Sacoolas didn’t immediately return messages from ABC News seeking comment.

“We have worked closely with our U.K. counterparts to find a mutually acceptable path forward,” a State Department spokeswoman said last month. “We continue to engage with them to find a reasonable resolution.”

According to court records, Dunn was riding his motorcycle in Croughton, Northamptonshire, when struck head-on by Sacoolas. The suit alleges that despite having a cellphone she didn’t call for help, and it was a passerby who called for an ambulance.

Dunn was transported to a hospital, where he later died from his injuries. Sacoolas admitted the accident was her fault and that she was driving on the wrong side of the road, according to the lawsuit.

Jonathan Sacoolas, Anne’s husband, owned the SUV she was driving at the time of the incident. They fled the country without notifying local authorities, the lawsuit claims.

Dunn’s family has quite publicly pressed officials on both sides of the Atlantic to provide them a chance at justice. Dunn’s parents, Tim Dunn and Charlotte Charles, accepted an invitation from President Donald Trump to meet him at the White House, however when they learned that Sacoolas was in another room waiting to meet them, they declined to meet her. The family insisted on meeting her in the U.K.

“The parents wanted none of this,” Seiger said of the lawsuit. “They have worked hard to avoid this. Mrs. Sacoolas and her advisers clearly do not consider the further misery this imposes on Harry’s family.”

Dunn’s death sparked rallies and protests around the world, and British Foreign Secretary Dominic Raab is applying to join the complaint as an amicus curiae to assist the family in a court battle, Seiger said.

“This extraordinary move has been welcomed by Harry’s parents,” Seiger said in the statement. Raab “will now be available to the parents and the court in order to provide assistance to them in securing the right outcome.”