There is a risk of "flagrant denial of justice" if Wikileaks founder Julian Assange is tried for rape in Sweden, his lawyer has told a UK court.
Geoffrey Robertson QC fears his client could face the death penalty if extradited to the US on separate charges relating to Wikileaks.
But prosecutors say any threat of unfair treatment would see the European Court of Human Rights intervene.
Mr Assange, 39, denies claims of sexual assault against two women.
His lawyers told the extradition hearing in London he was "willing and able" to co-operate with Swedish authorities, so no arrest warrant was needed.
'Trial by media'
They said the European Arrest Warrant under which he had been detained was invalid because he had not yet been charged.
Mr Robertson told Belmarsh Magistrates' Court there was a risk his client could be extradited to the US, or even Guantanamo Bay, and could face the death penalty as a result.
He said Swedish rape trials were regularly "tried in secret behind closed doors in a flagrant denial of justice".
In a document released by Mr Assange's defence team, they argued that:
Swedish prosecutor Marianne Nye is "not eligible" or an appropriate "judicial authority" to issue a European Arrest Warrant
The Swedes are guilty of an "abuse of process" as they have not demonstrated any intention to charge or prosecute Mr Assange
The application for a warrant is "disproportionate" as he is willing to co-operate and be interviewed by phone, e-mail or videolink
The arrest warrant paperwork is not valid as it does not "unequivocally" state that he is wanted for prosecution
The offences Mr Assange faces - unlawful coercion and sexual molestation - are not criminal acts under British law; and
Extraditing Mr Assange to Sweden would be a "real risk of a flagrant denial of justice" and a "blatant breach" of British constitutional principles.
Mr Robertson also said the extensive press coverage surrounding events risked a "trial by media".
He said front-page articles had described his client as a coward for refusing to return to Sweden.
"There's a danger this kind of media campaign, media vilification, will prejudice this secret trial," he told the court.
He also attacked the conditions Mr Assange could be held in if extradited to Sweden, saying the remand prison in Gothenburg had been criticised for its treatment of foreign prisoners.
Retired Swedish appeal court judge Brita Sundberg-Weitman, who was called as a witness, attacked Mr Assange's treatment by the authorities.
She said his case had been "extremely peculiar" from the start and criticised the authorities for revealing he was under investigation for rape.
"An authority must never use more harsh means than what is necessary for the objective. It is obvious this principle has not been respected here at all," she said.
"I can hardly imagine how, on suspicion of a sexual offence, you can do more harm to a person than has been done in this case.
"He [Mr Assange] is famous all over the world as a rapist and he has not even been charged."
But Clare Montgomery QC, representing the Swedish authorities, argued the Australian must face charges of rape and sexual molestation following the accusation of two women.
She told the court rape is one of 32 offences that warrants extradition, and Mr Assange was accused of having sex with one woman without a condom, despite her saying she would only consent if he wore one.
The other woman's claims implicitly suggested a lack of consent, she added.
"Mr Assange, by using violence, forced Miss A to endure him restricting her freedom of movement, taking hold of her arms, forcefully spreading her legs and lying on top of her," she said.
"Violently forcing yourself on someone and causing them to endure your lying on top of them can only be understood as violent, unlawful coercion, as action taken without... consent."
She also denied Swedish prosecutor Ms Nye was not authorised to issue the arrest warrant and said Mr Assange was wanted for prosecution not merely interrogation.
The whistle-blowing website has been used to publish leaked US diplomatic cables, as well as other sensitive material from governments and high-profile organisations.
Mr Assange arrived at court under an intense media spotlight, and supported by a number of high-profile campaigners including Bianca Jagger, Jemima Khan and veteran politician Tony Benn.
The Australian had his bail conditions amended so he could leave his adopted home in Norfolk to spend the night in Paddington, west London.
Several witnesses are expected to be called to court on Tuesday, and district judge Howard Riddle may yet reserve his judgement to a later date.
Mr Assange was released on bail by a High Court judge just before Christmas after spending nine days in Wandsworth prison.
He denies sexually assaulting two female supporters during a visit to Stockholm in August and claims the inquiry is politically motivated.
The extradition hearing is expected to last two days.
