An international "wanted" notice has been issued for an American woman charged with allegedly causing the death by dangerous driving of motorcyclist Harry Dunn.
The notice means that if Anne Sacoolas leaves the US, she faces arrest for allegedly running the teenager over while driving on the wrong side of the road near an RAF base in Northamptonshire last August.
In an e-mail sent by Northamptonshire Police, the 19-year-old's parents were told the suspect is "wanted internationally" and "should she leave the USA the wanted circulations should be enacted".
Family spokesman Radd Seiger told Sky News the move was a "huge step towards getting justice for Harry", declaring: "Be in no doubt, this means she is coming back."
Speaking to Kay Burley@Breakfast, he added: "The relevance of this is she is now a fugitive on the run. She can never set foot outside the United States again without being arrested.
"So the real question this morning is: is the United States, the leader of the free world, really going to be the country that stands for harbouring fugitives?"
Mr Dunn's mother, Charlotte Charles, told the same programme: "It's a big step in the right direction, for sure it is.
"We still feel we've got a way to go, but Anne Sacoolas needs to realise that she needs to come back now. It's time.
"She should never have gone back in the first place to the USA and she needs to come back and give us an opportunity to start to rebuild our lives."
Mr Dunn, 19, died in a head-on crash outside RAF Croughton while riding his motorcycle.
Ms Sacoolas, 42, the wife of a US intelligence officer, claimed diplomatic immunity and returned to the US. Sky News has confirmed she had a background in the CIA.
In December, following a public outcry, the Crown Prosecution Service (CPS) charged Ms Sacoolas with causing Mr Dunn's death by dangerous driving.
But the following month US secretary of state Mike Pompeo declined an extradition request from the British government - something Boris Johnson described as a "denial of justice".
The prime minister's spokesman restated that position when asked about the "wanted internationally" notice on Monday.
"She should return to the UK, we have made this clear to the US, including the prime minister to President Trump," he said.
A CPS spokesman said: "In December 2019 the CPS authorised Northamptonshire Police to charge Anne Sacoolas with causing death by dangerous driving.
"Our aim continues to be that Mrs Sacoolas stands trial in this country. We will continue to do everything we can to seek to ensure that happens.
"We are unable, however, to give any explanation of what steps may or may not be taken, because to do so may compromise operational effectiveness."
Amy Jeffress, Anne Sacoolas' lawyer, said in a statement after the charges were announced that her client would not return to the UK to face them because the potential 14-year sentence was "not proportionate" for what was "a terrible but unintentional accident".
"Anne is devastated by this tragic accident and continues to extend her deepest condolences to the family," the lawyer said.
"Anne would do whatever she could to bring Harry back. She is a mother herself and cannot imagine the pain of the loss of a child.
"She has cooperated fully with the investigation and accepted responsibility… This was an accident, and a criminal prosecution with a potential penalty of 14 years' imprisonment is simply not a proportionate response."
Mr Dunn's parents, Tim Dunn and Charlotte Charles, have vowed to keep fighting for justice for their son, at one point suggesting the UK "swap" Prince Andrew for Ms Sacoolas.
The Duke of York is wanted in the US by investigators looking into the case of deceased paedophile financier Jeffrey Epstein.
Last week, the Dunn family told Sky News they are issuing a complaint to the CPS over what they call their "inhumane" treatment.