If the court rejects his case, the 40-year-old Australian will have exhausted all his options in Britain but he could still make a last-ditch appeal to the European Court of Human Rights, prosecutors have said.
The Supreme Court, England’s highest, granted Assange permission to appeal in December.
It said his case raised an issue of “great public importance”, namely whether Sweden’s state prosecutor had the right to sign the European arrest warrant under which he was held.
The case will be considered by seven judges, rather than the usual five.
The Supreme Court usually takes about 10 weeks to deliver a judgement but the parties have requested that this case be speeded up.
Wednesday marks 421 days since the arrest of the former computer hacker, who has been living under tight bail conditions at the country mansion of a wealthy supporter in Norfolk, eastern England.
Assange was arrested in Britain in December 2010 after two women made allegations of sexual molestation and an accusation of rape in Sweden, which he strongly denies.
He says the sex was consensual and claims the allegations are politically motivated, linked to WikiLeaks’ release of hundreds of thousands of classified US files about the wars in Iraq and Afghanistan, as well as diplomatic cables.
Assange’s extradition to Sweden was initially approved by a lower court in February. An appeal to the High Court was rejected in November, but it subsequently granted him permission to appeal to the Supreme Court.
If this appeal fails, the WikiLeaks founder will have only one other option to stop his extradition — an appeal to the European Court of Human Rights in Strasbourg.
“If the ECHR takes the case then his current bail conditions would remain in force and he would remain in the UK until the proceedings at the ECHR have concluded,” the Crown Prosecution Service said in a commentary on the case.
“If the ECHR declines to take the case then he will be extradited to Sweden as soon as arrangements can be made,” England’s state prosecutor said.
Concerning Assange’s case before the Supreme Court, Julian Knowles, an extradition law specialist with the Matrix Chambers law firm, said the question of whether a public prosecutor was a valid judicial authority had been comprehensively tested.
“The courts have always reached the clear answer that while it may look odd to English eyes … European systems don’t have the same structure,” he was quoted as saying Tuesday in The Guardian newspaper.
“The courts have always said that to make extradition work, you have to be flexible in your approach to what extradition is.”
Were Assange to win, the consequences would be “very profound”, he said.
“It would basically mean, until the law is rewritten, that extradition to Europe (would) become very difficult, if not impossible.
“Because in the vast majority of European extradition requests, the arrest warrant is issued not by a court, as it would be in England, but by a prosecutor.”
Assange announced last week that he was launching his own television chat show and promised interviews with “key political players, thinkers and revolutionaries”.
No guests have been unveiled, but a statement on the WikiLeaks website said the show would go on air in mid March in 10 weekly half-hour episodes.
Russian state television channel RT said it had the rights to show the episodes first.
Formerly known as Russia Today, the English-language channel is funded by the Russian government.