The family of Harry Dunn has urged the UK government not to extradite Julian Assange to the US while Washington refuses to return the suspect in his death to Britain.
Mr Dunn died in a head-on crash with a car while riding his motorbike near RAF Croughton in Northamptonshire on 27 August.
Anne Sacoolas, the suspected driver, was charged with causing the 19-year-old's death by dangerous driving in December.
Last month, US secretary of state Mike Pompeo rejected extraditing Sacoolas.
She had claimed diplomatic immunity and left the UK for America after the collision, sparking a huge outcry.
Her husband is thought to be a US intelligence officer but she was understood to have been at the base as a spouse only and had no official role while she was in the UK.
However, there are unconfirmed reports Sacoolas was a former CIA spy.
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A day before the hearing into Washington's extradition request over Assange, Mr Dunn's family has called on Foreign Secretary Dominic Raab to stop the process.
Dunn family spokesman Radd Seiger said the principle of "reciprocity" is at the heart of any extradition treaty, which the US is "failing to abide by" over Ms Sacoolas.
He said: "Despite its disgraceful refusal to extradite Anne Sacoolas, the US continues to seek the extradition of people in the UK such as Julian Assange.
"In doing so, they are demonstrating an extraordinary amount of hypocrisy.
"As Dominic Raab told us when we met with him on January 27, 'we are reviewing all options'. We want him now to exercise the option of not extraditing Julian Assange to the US."
Assange, 48, is being held in Belmarsh Prison in south east London and is wanted in the US to face 18 charges over the publication of US cables a decade ago.
If found guilty, he could face a 175-year prison sentence.
Mr Dunn's family has previously called for the Duke of York to co-operate with law enforcement in the US amid allegations around Prince Andrew's friendship with convicted sex offender Jeffrey Epstein, who was found dead in a Manhattan jail cell last August.
A host of celebrities including Pink Floyd's Roger Waters and fashion designer Vivienne Westwood joined a rally opposing Assange's extradition in central London on Saturday.