Osama bin Laden's son-in-law on Friday asked a New York court to throw out terrorism charges against him, partly on the grounds he had been tortured on the flight that brought him to the United States.
In a motion seeking the dismissal of the case, lawyers for former Al Qaeda spokesman Sulaiman Abu Ghaith also claimed US officials had colluded with Iran over his detention there for more than a decade after the 9/11 attacks.
The move marks the first salvo of a landmark legal battle in which Abu Ghaith's lawyers will seek to challenge the US government's conduct in the "war on terror."
Prosecutors declined to comment on the dismissal motion. They have three weeks to respond, and the judge then has two weeks to set a date for a ruling or a hearing on the issues raised.
Abu Ghaith was detained by US agents in Jordan at the end of February and flown to New York. He was indicted on March 1 on a single count of conspiracy to kill US nationals.
That move was decried by prominent Republicans who said he should have been treated as an enemy combatant and sent to Guantanamo Bay -- though human rights groups welcomed President Barack Obama's decision to seek a civilian trial.
Abu Ghaith, a 47-year-old Kuwaiti national, is best-known for his incendiary statements alongside bin Laden and Ayman al-Zawahiri in the immediate aftermath of 9/11.
In a speech cited by the US government indictment, Abu Ghaith defended the attacks and warned Americans the "storms shall not stop, especially the airplanes storm."
The defense team argues Abu Ghaith has effectively been declared guilty -- on the basis of his "mere association" with bin Laden -- of a crime that carries a maximum sentence of life imprisonment.
They deny that his fiery rhetoric reflects direct involvement in any plot to kill Americans.
The motion presented to a US District Court in Manhattan Friday seeks the dismissal of the charges, most notably for violation of due process and the defendant's rights under the Speedy Trial Act.
The submission says Abu Ghaith was interrogated on the flight from Jordan under "capture shock" tactics designed to induce extreme vulnerability and terror in their client.
The tactics included being stripped naked, shackled and subjected to sensory deprivation through the use of blackout goggles and ear coverings, which the defendant says were refitted whenever he stopped answering questions.
The dismissal motion also alleges Abu Ghaith could have been brought to trial much sooner, given that the US had been able to secure the smooth transfer of other Al Qaeda suspects from Iran in the years following 9/11.
Abu Ghaith left Afghanistan for Iran around the end of 2002 and was held there until travelling to Turkey in early 2013. After being detained there, he was put on a plane to Kuwait but was arrested during a stopover in Jordan.
His lawyers said the US was always aware of his whereabouts, and they are seeking the disclosure of all official documents related to contacts with Iran to explain the more than 11-year delay before he was moved to US NATO ally Turkey.
They argued Abu Ghaith's chances of a fair trial have also been compromised by the killings of potential witnesses in US drone attacks, as well as by other assassinations of Qaeda leaders, including that of bin Laden himself.
And they say other witness testimony has been compromised by the well-documented use of torture at Guantanamo.
The defense also argued the charges should be thrown out on grounds that the relevant five-year statute of limitations has been violated and that the terms of the indictment are so vague that Abu Ghaith's constitutional right to be made aware of the detailed charges against him have been infringed.
In light of the torture claims, the judge was asked to rule inadmissible a 21-page FBI report largely based on the defendant's statements made during his 13-hour in-flight interrogation.
Defense lawyers also requested that several sections of the indictment relating to bin Laden and the 9/11 attacks be struck down, saying they are likely to prejudice a jury in a trial to be held close to the site of the 2001 attacks on New York.
Earlier this month, Abu Ghaith's defense team unsuccessfully petitioned the court to issue a restraining order formally restricting the US government from monitoring their communications amongst themselves, with Ghaith and his family or with potential witnesses.
The request, lodged in response to Edward Snowden's revelations about the scale of US surveillance activities, was dismissed by the judge, who said that, even if such monitoring was taking place, there was no evidence it would be used to help the prosecution.