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Don Arias stormed out of the meeting with the defense lawyers at this U.S. Navy base after less than 15 minutes. He was soon followed by three others who also lost family members in the 9/11 terror attack.

They had agreed to meet with lawyers appointed to defend five men charged in the attack. It was an effort at outreach the attorneys hoped would give an understanding of their difficult role. Instead, it stoked the anger of people who have watched with frustration as legal delays mount in the case.

"I am very angry at these people," Arias, whose 37-year-old brother, Adam, was killed in the World Trade Center, said of the defense teams. "It is one thing to have a trial. It is another to drag it out, and drag it out and drag it out."

The reason for his frustration became apparent Thursday morning. A four-day pretrial hearing ended with the case derailed by a new issue, an apparent FBI investigation of the defense.

Claudia Jacobs, whose brother Ariel also died in the World Trade Center, said the families of victims had hoped to see more progress.

"You just realize that we have a special interest in that it does in some ways prolong our pain," said Jacobs, part of a small contingent chosen by lottery to view the legal proceedings at Guantanamo.

This was the 10th round of pretrial hearings since Khalid Sheik Mohammed, who has portrayed himself as the mastermind of al-Qaeda's 9/11 plot, and four co-defendants were arraigned nearly two years ago before a military commission on charges that include terrorism and nearly 3,000 counts of murder in violation of the law of war.

The prosecution hoped to start jury selection early next year, but that now seems impossible as a judge conducts an inquiry into the scope and possible legal implications of the apparent investigation of the defense team and legal fights loom over classified evidence from the CIA and other issues.

The case has long been stalled, initially by the U.S. government's decision to hold the men in secret detention for up to four years and later by legal challenges and a fight over whether to try them in civilian or military court on charges that could bring the death penalty.

Army Maj. Jason Wright, a lawyer for Mohammed, said he understands frustration over the delays but says the government is largely to blame.

"If they had brought Mr. Mohammed to trial on March of 2003 when he was captured, one would think the case would certainly have been resolved one way or the other by now," Wright said.

The chief prosecutor, Army Gen. Mark Martins, shrugged off suggestions the case could be resolved more quickly in a civilian court, noting Congress has barred any venue but Guantanamo. "When each of us was assigned to this important mission, we were prepared for a marathon."

In December, the judge halted progress on pretrial motions because prosecutors wanted to determine the mental competency of defendant Ramzi Binalshibh after his repeated outbursts in court. That was supposed to be the subject of a hearing this week until his attorney disclosed that a member of his defense team had been interviewed by two FBI agents and was asked about the conduct of other defense teams.

The judge, Army Col. James Pohl, is conducting a formal inquiry into the questioning, which apparently was triggered when an essay by Mohammed was released by his defense team without passing through normal security review.

Defense lawyers say the FBI investigation could create a conflict of interest between them and their clients, and may require appointing independent counsel for each team, something that could take months because of the need to obtain security clearances. Some could even have to step down depending on the scope and nature of the FBI investigation.

A likely drawn-out fight is also emerging over classified evidence about the treatment of the defendants while in CIA custody at secret overseas detention facilities. Lawyers say they will seek the evidence that the judge has ordered the government to turn over in a separate trial over the attack on the USS Cole.

Jacobs, who came from her home in the Boston area to observe the proceedings, found it hard to watch. "What you should never see made is sausage and legislation. I would add the 9/11 hearings to that."

Bill McGinly, whose son Mark was killed in the World Trade Center, was more upbeat. "I am disappointed that there are so many delays in all this, but I am encouraged with what little movement there was this week that at least it's going forward," said the resident of Vienna, Virginia.

Arias, a retired Air Force officer from Panama City, Florida, said the week left him drained. "Let's get on with it."