The parents of 19-year-old Harry Dunn have called for the suspect in the crash that killed him to be charged.
Northamptonshire Police handed a file to the Crown Prosecution Service (CPS) on Friday after interviewing suspect Anne Sacoolas in the US.
Mr Dunn died in hospital after the crash outside RAF Croughton in Northamptonshire in August.
His mother said: "It would be ludicrous to not bring charges when there's that much evidence for the CPS to see."
Speaking on the Victoria Derbyshire programme, Charlotte Charles said: "It's baby steps all of the time but we are getting closer [to justice]."
Mr Dunn's motorbike crashed with a car owned by US citizen Mrs Sacoolas, the 42-year-old wife of a diplomat, outside the Northamptonshire airbase on 27 August.
Mrs Charles and Harry's father, Tim Dunn, are campaigning for justice after Mrs Sacoolas returned to the US, claiming diplomatic immunity, shortly after the crash.
They travelled to the US as part of their campaign and have been calling for her to answer questions over their son's death.
Mr Dunn told the BBC Two programme: "They've got to [press charges]
"With the evidence that we know about as a family, with the CCTV.... I can't see how there can't be charges brought."
The CPS will now make a decision based on the evidence in the file whether to bring charges forward against anyone involved in the case.
The BBC has asked the CPS for comment.
Mr Dunn's family has announced plans to sue Mrs Sacoolas, and said lawyers would also look at "lawless misconduct" of the US administration.
Legal action has also been launched against the Foreign and Commonwealth Office and the family intends to refer Northamptonshire Police to the Independent Office for Police Conduct over its handling of the investigation.
Mrs Charles said: "We can't grieve until we've got the truth, for the sake of Harry's legacy and everyone else that this could possibly happen to, we couldn't live with ourselves if it happened again and we hadn't tried to do something.
"That's where we're getting our fight from."