Northamptonshire Police's top chiefs say they will "never slow down" in pursuing justice for Harry Dunn's family.
It has been a week since Northamptonshire Police revealed in an official statement that an American suspect in the death of 19-year-old Harry Dunn had left the country by claiming diplomatic immunity.
Since the statement last Friday (October 4), thousands of people have called for the US to revoke Anne Sacoolas' status and return her to the UK to face justice.
But tensions were high yesterday (October 10) after President Donald Trump accidentally flashed a secret US State Department cue card during a press conference - which read that the suspect "will not return to the UK".
It also comes after Harry's family reportedly branded a meeting with secretary of state for foreign affairs Dominic Raab "a publicity stunt" and say they feel "in the dark" about how the diplomat scandal is progressing.
Northamptonshire Police and Crime Commissioner Stephen Mold said: "There's historically been a very strong special relationship between the US and the UK - and although Donald Trump is, shall we say, the current custodian of this relationship I hope that common sense will prevail.
"I think in its totality there's never going to be any winners in this. Northamptonshire Police will do all we can do to get justice for Harry and his family.
"I would repeat the force's message that she should do the right thing as a mother and return to the UK to help Northamptonshire Police with its investigation.
"Don't rule out extradition, let's put it that way."
It comes after the force's chief constable Nick Adderley spoke on BBC Radio 4 this week to appeal to Mrs Sacoolas - who is the wife of a US ambassador - to "do the right thing".
Chief Constable Adderley told the Chronicle and Echo: "It's always tragic when dealing with a grieving family and throughout this period of grief what his family is quite rightly looking for is some hope.
"I admire their tenacity in pursuing their cause and I want to give them the reassurance that we're not slowing down in our endeavours legally or lawfully to see justice be done.
"My issue with Trump is that it was upsetting for the family but also upsetting for the judicial process. We have not explored all avenues yet so to see that note would give the impression that this is a done deal is upsetting.
"I want to make the point that here at Northamptonshire Police we are not giving up hope. We are speaking to the American embassy every day and know that the British Government is working incredibly hard."
Meanwhile, it has been revealed this week that after the crash that killed Harry, Northamptonshire Police was not told that Mrs Sacoolas had left the country for weeks after, and do now know how or when she left the UK.
Chief constable Adderley said: "I have looked at the timeline and the files surrounding this case and I'm more than content that Northamptonshire Police has done everything it could have done lawfully to move at speed and complete our enquiries."
Harry Dunn, 19, was killed on the B4071 Park End, near Croughton, after his motorcycle collided head-on with a black Volvo SUV allegedly driven by Mrs Sacoolas.
It has been reported that the 47-year-old American was driving on the wrong side of the road at the time.