A French judge has requested access to the US-run Guantanamo Bay prison camp to investigate allegations of torture made by three French nationals. The three men were former detainees at the US military facility in Cuba but returned to France in 2004 and 2005.

Sophie Clément, an investigative magistrate, has submitted a request to US authorities to see "all documents relating to the justification and modalities of (US) armed operations in Afghanistan and Pakistan, and to the treatment of persons arrested during these operations," in a document signed Jan. 2.

Investigative magistrates in France act as independent legal detectives, probing possible crimes in certain sensitive cases. Magistrate Clément is known in France for her previous investigation of crimes committed by the late Chilean dictator Augusto Pinochet.

The magistrate is looking to shed light on possible acts of torture during the detention at Guantanamo of defendants Mourad Benchellali, Nizar Sassi and Khaled Ben Mustapha, and would potentially include questioning of US military personnel.

"This [request] is unprecedented," said Philippe Meilhac, the lawyer for former prisoner Khaled Ben Mustapha. "But it’s normal that the judge leading the investigation approach those concerned at Guantanamo to verify these claims.”

To Guantanamo and back

Arrested in late 2001 on the Afghan-Pakistani border, the three men were sent to the notorious Guantanamo Bay prison. They were detained there for periods of between 11 and 17 months, before returning to France.

Benchellali has reported that before being taken to Cuba he was taken to Afghanistan where he states he was beaten and forced to strip, and then made to lie on top of other naked men while US soldiers took photos.

Ben Mustapha reports that after his arrest he was also taken to Afghanistan where he was subjected to sexual abuse, which judge Clément said in the legal documents could lead to rape charges.

All three former inmates told of being beaten during interrogations.

They were sentenced by a French court to one year in prison on terrorism charges in 2011 but have said they will appeal that decision.

‘Nothing guarantees cooperation’

"Nothing guarantees the US authorities to cooperate," Meilhac admitted, “But I hope they will.”

According to the French lawyer, the legal request was especially sensitive because it included the possibility of questioning US soldiers.

Nevertheless, Meilhac hoped magistrate Clément’s move would set a precedent and spur other European countries to look into the torture claims made by other former Guantanamo inmates who hold European passports.

Meilhac even invoked the possibility of a trial of Guantanamo personnel charged with torture in abstentia, a possibility under French law. In 2010 a court in Paris tried 15 Chileans linked to the Pinochet dictatorship in absentia, eventually convicting 14 of the accused.

The Guantanamo prison was opened in January 2002, under the administration of former US president George W. Bush, to jail suspected terrorists. A decade on, 171 prisoners remain there, despite President Barack Obama’s promises to close the camp.