WikiLeaks founder Julian Assange finds out on Wednesday if he can be extradited from Britain to Sweden over alleged sex crimes as the Supreme Court passes judgment after a marathon legal battle.
The internet whistleblower, who enraged Washington by releasing a flood of state and military secrets on his website, has been fighting deportation since his arrest in London in December 2010 on a European arrest warrant.
Britain's top court is his final avenue of appeal under UK law, after two lower courts ruled he should be sent to Sweden for questioning over allegations of rape and sexual assault made by two WikiLeaks volunteers.
But Assange, who will has been living under tight restrictions on his movement for 540 days, will have the option of a last-ditch appeal to the European Court of Human Rights if he loses.
His case rests on a single point -- that the Swedish prosecutor who issued the warrant for his arrest was not a valid judicial authority.
The 40-year-old Australian is expected to attend what will be a short ruling at the court in central London. The decision will be handed down at 0815 GMT, streamed live and published online.
The Supreme Court president will give a summary of the point of law raised by the appeal, the decision of the seven-judge court, and a brief explanation of its rationale.
Journalists and supporters attending the hearing in the building opposite the Houses of Parliament have been warned of airport-style security.
Swedish authorities argue that if his appeal is granted it could throw the fast-track European arrest warrant system into turmoil, with implications across the continent.
"It is prosecutors who issue arrest warrants (in Sweden). End of story," Karin Rosander of the Swedish prosecuting authority told AFP.
The white-haired former hacker has said he fears his extradition would eventually lead to his transfer to the United States, where US soldier Bradley Manning is facing a court-martial over accusations that he handed documents to WikiLeaks.
One week ago, Assange attended a film screening in London wearing a Kevlar Guy Fawkes mask.
"This may be my last time in public, so I thought I should start with a situation where you won't be able to see me anymore," said Assange, who since December 2010 has been forced to report to police daily and wear an electronic ankle tag.
A lower court in Britain initially approved Assange's extradition to Sweden in February 2011.
An appeal to the High Court was rejected in November, but Assange subsequently won permission to appeal to the Supreme Court, which heard two days of complex arguments in February.
If he falls at the last hurdle in Britain, Assange has the final option of going to the European Court of Human Rights, which would have to decide within 14 days whether it would take on the case.
"He must certainly make the appeal to the European Court of Human Rights, but more importantly for him, he must persuade them to issue an interim relief to issue an instruction to the United Kingdom to stop his extradition to Sweden," Anand Doobay of London law firm Peters & Peters told AFP.
Swedish authorities said that Assange would still be subject to arrest and extradition by other European countries, even if he wins in Britain.
The legal saga began in Sweden in August 2010 when Assange was accused of raping one woman by having sex with her while she was asleep, and of sexually assaulting another woman.
He insists the sex was consensual and says the charges are politically motivated.
Assange's controversial new talk show "The World Tomorrow" on Russia's state-funded RT cable broadcaster should not be affected whatever the court's decision, as he has pre-recorded 12 episodes.
WikiLeaks' exclusives have largely dried up, however, since the days when it won worldwide notoriety by releasing tens of thousands of diplomatic cables about the wars in Iraq and Afghanistan.
It came under fire last September for potentially endangering the lives of government informants by publishing an unredacted version of its archive of 251,000 secret US diplomatic cables.
Funding for the website has also crashed since Visa and PayPal stopped processing donations.