FORT MEADE, Md. — A Guantanamo Bay prisoner pleaded guilty Thursday to war crime charges in a pretrial deal aimed at limiting his sentence to 15 years for helping plan the suicide bombing of an oil tanker off Yemen in 2002 that killed a crewman and wounded a dozen others.
The deal was widely expected to give him time to testify against Abd al-Rahim al-Nashiri, who also faces terrorism charges in the tanker bombing and for allegedly orchestrating the 2000 Al Qaeda attack on the USS Cole in the Yemeni port of Aden that killed 17 sailors and wounded 37.
A military judge accepted the plea deal and found Ahmed al-Darbi of Saudi Arabia guilty of the five charges against him, including terrorism, attacking civilians, and hazarding a vessel for complicity in the Al Qaeda attack on the French-flagged MV Limburg. Under the deal, the sentence could be capped if he cooperates with authorities.
Darbi is a relative by marriage to one of the Sept. 11 hijackers who crashed a plane into the Pentagon. He has been at the prison in Guantanamo Bay, Cuba, since August 2002; the attack actually occurred two months later.
But prosecutors said he was an Al Qaeda operative who attended the group’s training camps and helped arrange the bombing by, among other things, buying small boats intended to be used to attack the tanker.
‘‘Mr. al-Darbi was not present . . . did not actually physically take part in the attack, but he is guilty’’ of the crimes under US law because he aided those who did, the presiding judge, Air Force Colonel Mark L. Allred, said as he repeatedly explained the law to Darbi. Speaking to Darbi through an interpreter, Allred said he could not accept the guilty pleas until he was sure the accused completely understood them. The judge spent close to two hours going over the case — charge by charge — and questioning Darbi on them.
Flanked by his civilian and military lawyers, the 39-year-old Darbi wore a white dress shirt and a tie and repeatedly answered ‘‘yes, your honor,’’ sometimes in English and sometimes in Arabic, to signify his understanding to Allred.
‘‘Do you understand that you are legally responsible for these actions?’’ Allred asked.
‘‘Yes,’’ Darbi said.
Allred said Darbi’s sentencing would not be held for 3½ half years.
If he complies with his part of the deal, his sentence could be limited to 15 years, minus the 3½ years that he will remain at Guantanamo Bay until sentencing proceedings.
‘‘Following sentencing . . . it is possible Mr. al-Darbi will be repatriated to the Kingdom of Saudi Arabia to serve the remainder of his sentence to confinement in a Saudi Arabian prison,’’ chief prosecutor Mark Martins said.
Allred said the plea deal also means Darbi waived his rights to a trial and an appeal, that he will not sue the United States on his capture, prosecution, and confinement, and that he will drop pending lawsuits.
The ruling Thursday gives Darbi at least a little more certainty about his future, said his civilian lawyer, Ramzi Kassem.
The arraignment was held in Cuba but was viewed by some journalists via closed circuit at Fort Meade military base near Baltimore.