More than 400 prospective jurors filled out questionnaires Wednesday aimed at gauging their eligibility for the first civilian trial of a Guantanamo Bay detainee after a judge assured them that they would remain anonymous.

U.S. District Judge Lewis A. Kaplan briefly spoke to two separate groups of possible jurors for the trial of Ahmed Khalfan Ghailani, who is charged in the 1998 bombing of two U.S. embassies in Africa that killed 224 people, including 12 Americans.

Kaplan said even he won't know the identity of potential jurors, who were identified only by a number. Anonymous juries are not unusual in federal court in Manhattan for trials involving terrorism or organized crime.

The judge told the groups that Ghailani was charged in connection with the bombings of the embassies, "denies all the charges against him" and was presumed innocent.

He warned them not to read, watch or listen to anything to do with the case and prompted a few chuckles when he added: "No tweets or whatever else folks do nowadays."

Ghailani and lawyers on both sides were not in the jury assembly room for Kaplan's remarks. He said a week earlier that he did not consider the filling out of questionnaires to mark the start of the trial.

Instead, it will begin Sept. 29 when a few hundred prospective jurors who remain after the questionnaires are reviewed will be brought to the courthouse for questioning about some of their answers. The judge planned to seat a jury of 12 people with six alternates and begin opening statements on Oct. 4, though he said the date was not definite.

"The great majority of you I will not have the pleasure of seeing again," Kaplan told a group of several hundred potential jurors in the afternoon.

A copy of the 30-page questionnaire was not immediately released publicly.

In summer submissions to the judge, defense lawyers and prosecutors made their recommendations for the questionnaire.

Defense lawyers asked to include questions that would ascertain whether potential jurors doubted their ability to be fair if they learned that the government claimed Ghailani was a member or associate of al-Qaida or if they had personal experiences or feelings arising from the Sept. 11, 2001, terror attacks.

They proposed asking: "On a scale of 1 - 5, how afraid are you that you, a family member, or anyone you are close to will be injured or killed in a terrorist attack?"

They also sought to ask whether people had personal experiences or feelings arising from any local, national or international act of terrorism and if they believe Islam supports violence to a greater extent than other religions.

In one submission in August, the lawyers wrote that jurors "each morning as they walk past the 9/11 crater, they will receive a startling reminder that terror can strike anywhere."

The lawyers then suggested that Kaplan include a question about a controversy over plans to build a mosque near the World Trade Center site, saying "such a topical question would quickly go to the heart of the potential fears and bias."

Prosecutors asked that the judge exclude questions about the ethnic background of jurors and their spouses, partners and roommates, saying such questions were intrusive and had no bearing on whether a juror can be fair. They also said it was "overly intrusive and objectionable" to ask whether jurors ever visit political websites or blogs.

Ghailani was accused by the government of being a bomb-maker, document forger and aide to Osama bin Laden, who is also charged in the indictment. Ghailani has pleaded not guilty and has denied knowing that the TNT and oxygen tanks he delivered would be used to make a bomb.

Four others were convicted for their roles in the bombings in federal court in Manhattan in 2001. They were each sentenced to life in prison.