WikiLeaks founder Julian Assange is due to hear if he has won or lost his High Court bid to block extradition to Sweden where he faces sex crime allegations.
His lawyers asked two judges to rule that extraditing the 40-year-old Australian would be "unfair and unlawful".
The Swedish authorities want him to answer accusations of "raping" one woman and "sexually molesting and coercing" another in Stockholm in August last year.
Assange, whose WikiLeaks website published a mass of leaked diplomatic cables that embarrassed several governments and international businesses, denies the allegations and says they are politically motivated.
The High Court in London is having to decide whether to uphold or overturn a ruling in February by District Judge Howard Riddle at Belmarsh Magistrates' Court, south London, that the computer expert should be extradited to face investigation. Judgment will be handed down by President of the Queen's Bench Division, Sir John Thomas, sitting with Mr Justice Ouseley.
The Assange legal challenge, which has attracted worldwide attention, centres on a European arrest warrant (EAW) issued by a Swedish prosecutor which led to Assange's arrest.
His QC, Ben Emmerson, argued at a two-day hearing in July that the prosecutor was not a "judicial authority" entitled to issue the EAW.
The warrant had also contained "fundamental misstatements" of what had occurred in Stockholm last August while Assange was in Sweden to give a lecture, said the QC.
Assange's encounters with two women who had made complaints involved consensual sex and would not be considered crimes in England, he argued. The EAW was misleading in its accusations that he had used violence or "acted in a manner to violate sexual integrity", said Mr Emmerson.
The side that loses the legal battle will have the opportunity to apply to take the case to the Supreme Court, the highest court in the land, on the grounds that it raises issues of general public importance.