The United Kingdom court overseeing the case of the Wikileaks founder, Julian Assange, on Monday is set to convene a two-hour hearing regarding America’s promises about what will — or will not — happen to Mr. Assange if he is extradited.

Mr. Assange is wanted in America for 17 counts of espionage and one count of computer misuse. Although Mr. Assange does not face charges that might receive a sentence of capital punishment, his attorneys have raised objections to his extradition on the grounds that he could end up being charged with and condemned for treason or another capital offense, once the Americans have him in custody.

In a previous extradition request, a U.K. court ruled that Mr. Assange would be too likely to kill himself if held in an American prison, citing the conditions of America’s federal institutions, such as the notorious ADX Florence, the “supermax” prison in Colorado where the convicted spy Robert Hanssen died last year. 

Despite that U.K. court ruling, in 2022 the then home secretary for the United Kingdom, Priti Patel, ruled that Mr. Assange could be extradited to America. Yet the extradition has been the topic of a legal battle since the decision.

The U.K., as a matter of policy, does not typically extradite prisoners to countries where they could face capital punishment, and Mr. Assange’s lawyers have argued that he is unlikely to survive extradition to America.

In February, Mr. Assange’s attorney submitted nine grounds to the high court hearing the case arguing that Mr. Assange’s extradition was unlawful. While the court rejected six of these, the judges overseeing the case agreed that three of them had an “arguable case” to be made.

Two of those grounds make the case that Mr. Assange would not enjoy the same right to free expression that American citizens enjoy, given his status as a foreign national. The third argument concerns the risk that Mr. Assange will face execution by the state, which is what the hearing Monday concerns. The judges cited concerns that Mr. Assange could be charged with an additional crime that carries the death penalty, such as treason. 

As evidence for this, the attorneys for Mr. Assange referred to comments made by Donald Trump in 2010, when the now former president said there “should be like death penalty or something” for the Wikileaks founder.

Mr. Assange has been evading American law enforcement since the publication of hundreds of thousands of classified documents on Wikileaks in 2010, documents allegedly supplied by Mr. Assange.

The leak included documents such as footage of a 2007 American airstrike on Baghdad titled “Collateral Murder,” which showed an Apache helicopter crew firing on and killing a group of civilians, including two Reuters journalists, before laughing about the casualties. The veracity of the footage was later confirmed to Reuters by an American defense official.

Mr. Assange was initially arrested in the U.K. in 2010 after Swedish officials told U.K. police that they wanted to question him about two accusations of sexual assault made against Mr. Assange. The case against him in Sweden was dropped in 2019, with authorities saying too much time had passed.

In 2012, Mr. Assange violated his bail and sought refuge in the Ecuadorian Embassy at London, where he would live until 2019, never venturing outside. 

He continued to operate from his sanctuary, though his direct involvement in Wikileaks was unclear. In March 2016, Wikileaks released a trove of Secretary Clinton’s personal emails that she’d kept on a private server while secretary of state. Then, in July and August 2016, Wikileaks released two tranches of confidential emails from the Democratic National Committee, which showed how committee officials favored Mrs. Clinton’s presidential bid over that of Senator Sanders.

In August 2016, Mr. Assange went on Dutch television and fueled speculation around a theory surrounding the death of a Democratic National Committee staffer, Seth Rich. The unsubstantiated theory had become popular among some in the orbit of Mr. Trump, such as an informal advisor to the then presidential candidate, Roger Stone.

Proponents of the theory, like Mr. Stone and the Russian Embassy in the U.K., suggested that the DNC was behind the murder of Rich as well as other murders. 

In 2019, Mr. Assange was expelled from the Ecuadorian Embassy after a falling out with his hosts. Upon his being expelled, British authorities arrested him and prosecuted him for violating the terms of his bail.

At court Monday, attorneys for America are expected to make overtures to assuage the doubts of the British court managing the case, which has said it will not extradite Mr. Assange unless the Americans agree that he will not be executed.

Although American officials have reportedly already said that they won’t seek the death penalty against Mr. Assange, it’s not clear whether the court will grant America’s request.

In a note obtained by the New York Times,  American officials said, “A sentence of death will neither be sought nor imposed on ASSANGE.”

“The United States is able to provide such assurance as ASSANGE is not charged with a death-penalty eligible offense, and the United States assures that he will not be tried for a death-eligible offense,” the note reads.

If the high court rules in favor of Mr. Assange on Monday, he will be granted a full appeal, likely at a later date. 

Outside groups like Amnesty International have also called into question the seriousness of America’s guarantees, with a legal advisor to the group, Simon Crowther, saying that “authorities in the U.S. seem hell-bent on making an example of Assange for exposing their alleged war crimes, rather than upholding the values of freedom of expression.”

“If extradited, Assange potentially faces dozens of years of incarceration and the risk of prolonged solitary confinement in a maximum-security prison with poor health services,” Mr. Crowther said in a statement. “His safety and well-being simply cannot be guaranteed.”

President Biden has also said that the administration is “considering” dropping the case against Mr. Assange, in response to a question about a request made by the Australian government. Mr. Assange is an Australian citizen.

Although Mr. Assange is not charged with a capital offense, others have been executed for espionage charges, albeit not in decades. 

The last people to be executed under espionage charges in America were Communist Party members, Julius and Ethel Rosenberg, an American couple who were executed in June 1953 after being convicted of sending information about atomic weapons to the Soviet Union.