The WikiLeaks founder’s extradition hearing began in London on Monday.

LONDON —
The family of a British teenager killed in a crash involving the wife of an American diplomat has called for the United Kingdom to block the extradition of WikiLeaks founder Julian Assange to the U.S.

The U.S. has declined the U.K. government’s request to extradite Anne Sacoolas, who was allegedly driving the car that collided with Harry Dunn’s motorcycle last August. By doing so, the U.S. government “has launched the single greatest attack on the so-called special relationship between the countries in modern memory,” Radd Seiger, an adviser and spokesperson for the Dunn family, said in a statement Saturday.

Seiger said the U.S. “is not behaving like an ally” and is “demonstrating an extraordinary amount of hypocrisy” in continuing to seek the extradition of people in the U.K., including Assange, whose extradition hearing began in a London courthouse on Monday.

The 48-year-old Australian spent seven years in self-imposed exile inside the Ecuadorian Embassy in London until he was evicted in April 2019 and subsequently arrested by British police for having jumpedbail in 2012. U.S. authorities want to try Assange for 17 charges of espionage and one charge of computer hacking, all of which carry a maximum sentence of 175 years in prison.

“The principle of reciprocity is at the core of any extradition treaty,” Seiger said. “In accordance with the principle of reciprocity which the U.S. is failing to abide by, on behalf of Harry Dunn’s family and the millions of concerned citizens in the U.K., I now demand that the U.K. authorities block any further extraditions to the U.S., including the one of Julian Assange, until such time as Anne Sacoolas is extradited and back on U.K. soil facing the justice system here.”

“No one is above the law,” Seiger added, “and no one must be allowed to evade justice if they manage to flee a country, whether diplomat or not.”

When asked for comment on Seiger’s remarks, a U.K. government spokesperson told ABC News in a statement, “Julian Assange is subject to an extradition request from the United States of America. He is accused of offenses including computer misuse and the unauthorized disclosure of national defense information. As this case is now before the courts, it would be inappropriate to comment further.”

A spokesperson for the U.S. Department of State declined to comment Monday.

ABC News has reached out to Sacoolas’ attorney for comment.

Dunn was riding his motorcycle along a roadway in the village of Croughton, England, on the night of Aug. 27, when a car traveling in the opposite direction on the wrong side of the road hit him head-on. The 19-year-old was taken to a nearby hospital where he died soon after, according to the Northamptonshire Police.

The driver of the car was Sacoolas, a 42-year-old U.S. citizen married to an American diplomat who worked at a British military station housing a base operated by the U.S. Air Force. The fatal collision occurred less than a mile down the road from the base.

Sacoolas attempted to help Dunn after the collision and waved down another car, according to a previous statement from Sacoolas’ attorney, Amy Jeffress. She remained at the scene and spoke with first responders when they arrived. She also met with local police the following day and gave a voluntary interview several weeks later, Jeffress said.

Sacoolas and her family fled the United Kingdom about three weeks after the crash when U.S. authorities confirmed her diplomatic immunity, which protects diplomats and their family members from prosecution or lawsuits under the host nation’s laws. The controversial move sparked a diplomatic rift between the two countries. Dunn’s parents have repeatedly called on Sacoolas to return to England to face them and the police investigation.

Northamptonshire Police officers traveled to the United States in October to interview Sacoolas again. In December, the United Kingdom’s Crown Prosecution Service authorized the Northamptonshire Police to charge Sacoolas with causing death by dangerous driving, paving the way for extradition proceedings to begin.

But U.S. Secretary of State Mike Pompeo turned down the extradition request in January, a decision which the U.K. government condemned.

“Anne is devastated by this tragic accident and would do anything she could to bring Harry back. She continues to grieve for Harry and his family,” Jeffress told ABC News in a statement on Jan. 10. “The U.S. government has made clear they will deny any extradition request and will uphold the longstanding agreement of diplomatic immunity between our two countries. We remain willing to work with the U.K. authorities to identify a path forward.”