Government lawyers have asked the tribunal — a military court presided over by three senior officers — to judge Al-Nashiri guilty, citing his confession to the crime. The US prosecutors are seeking the death penalty.

But the leader of Al-Nashiri’s defense team, Navy Lt. Cmdr. Stephen Reyes, claims that Al-Nashiri’s admission of guilt was obtained while he was subjected to aggressive interrogation techniques, and is seeking to have the Saudi’s case dismissed on the grounds that his confession was obtained under torture — a violation of US law.

The CIA captured Al-Nashiri, 46, in the United Arab Emirates in 2002 and secretly detained him for four years. But the CIA has refused to discuss the circumstances of his detention or the kinds of “enhanced interrogation techniques” under which the onetime top Al-Qaeda lieutenant offered his confession.

Pressed by the media, the CIA recently acknowledged that Al-Nashiri was held incommunicado at an undisclosed "black site" (a secret facility, usually outside the US) where interrogators seeking information about other potential terror attacks subjected him to “waterboarding” (repeated water dunkings that mimic drowning), placed a handgun beside his head, and operated an electric drill near his naked body in an intimidating manner. CIA interrogators also threatened to harm Al-Nashiri’s family.

Reyes claims that the CIA’s use of these techniques nullifies the American government’s case against his client, citing the Military Commissions Act of 2009, enacted by President Barack Obama, which prohibits the use of statements obtained through duress.

A statement recently issued by the Pentagon seems to acknowledge that the legal grounds for Reyes’ claim may have some merit. “No evidence obtained by torture or cruel, inhuman or degrading treatment shall be admissible in a military commission,'' said Army Lt. Col. Tanya Bradsher, a Pentagon spokesperson.

The case before the Guantanamo tribunal also charges Al-Nashiri with planning the Oct. 6, 2002 attack on a French civilian oil tanker, the Limburg, and with planning an attack on another American Navy destroyer, USS The Sullivans, as it refueled in Aden on Jan. 3, 2000. The Sullivans attack did not take place.

Al-Nashiri has previously acknowledged that he obtained the small boat that was used to deliver the explosives to the USS Cole. But he said he thought the water craft was to be used for a fishing trip and was not aware it was intended as a vehicle for a suicide bombing

Al-Nashiri has also told reporters that the pain inflicted on him by his CIA interrogators was often so severe he would simply “invent” stories to get them to stop. He said one of his invented stories included details on how Osama Bin Laden had obtained a nuclear bomb.