A legal fight against extradition to the United States by a man described by an FBI special agent as "the largest facilitator of child porn on the planet", has been hit with further delays.

Lawyers for Eric Eoin Marques, 30, said tests carried out on him in prison last month confirmed he has Asperger's syndrome, a condition which is part of the autism spectrum.

Mr Marques is wanted in the US on four charges linked to website images described as being extremely violent and graphic.

He is fighting extradition proceedings in the High Court, while a separate judicial review is being carried out into Ireland's decision not to prosecute the case here.

His lawyers denied the medical evidence, which has only just been introduced, was a delaying tactic, but insisted they had been pressing medical experts for some time to carry out the proper tests.

They had become suspicious about Mr Marques' mental condition sometime around last Christmas, his solicitor Caroline Egan said.

She asked Professor Patricia Casey, a psychiatrist from Dublin's Mater Hospital, to assess him.

The doctor agreed to bring forward an appointment by several months while medical files revealed he had a history of psychiatric care since he was five years old, the court heard.

After Prof Casey assessed Mr Marques she asked Odhran McCarthy, a senior clinical psychologist in the Mater Hospital, to carry out hours-long follow up tests, including observations and pen and paper exercises.

These were done in the Midlands Prison in Portlaoise.

Mr Marques has been remanded in custody since his arrest in August 2013, after the FBI and gardaí deemed he was a flight risk or likely to destroy evidence if released.

A report, dated 7 May, confirmed a diagnosis of Asperger's syndrome, Ms Egan told the court.

Asked if it was a delaying tactic, she replied: "Absolutely not."

Ms Egan said she had persisted in getting the medical tests done and was obliged to the psychiatrist and psychologist who had brought forward the examination by several months.

State prosecutors have indicated they would like to have their own independent assessments carried out.

Judge Aileen Donnelly said it was extremely unsatisfactory that medical reports and other submissions had yet to be introduced in the lengthy case.

Four days had been set aside this week for the hearing.

Judge Donnelly said she was very reluctantly allowing fresh affidavits to be admitted in the proceedings and remanded Mr Marques in continuing custody to 29 June, when he is to appear before the same court.

Mr Marques, with an address in Mountjoy Square, Dublin, has both Irish and US citizenship.

He has previously denied being the owner and administrator of an anonymous hosting server called Freedom Hosting where the FBI claim thousands of members allegedly posted millions of images of child abuse.

Last November, he told the Director of Public Prosecutions he would plead guilty - in Ireland - to charges relating to conspiring to distribute and advertise child abuse images, as well as advertising and distributing child pornography.

But the DPP Claire Loftus has indicated she would not bring proceedings against him in Ireland.