A secret chamber guarded zealously by U.S. marshals. An elevator that stops on the first floor, but only with a key. Private passageways through which witnesses are whisked away.

Federal grand juries in Alexandria meet in a virtual bunker, with nearly the entire grand jury area on the first floor at U.S. District Court sealed off from the rest of the building.

The process is far more secretive than that at most courthouses across the country and, some experts said, deviates from the government's own guidelines specifying that grand jury areas must be "accessible through public circulation" and in an area with light public traffic.

Grand jury proceedings historically have been conducted secretly, and no one suggests that should change. But open-government advocates and some defense lawyers are critical of what they see as the excessive secrecy in Alexandria, saying it makes it harder for journalists -- and ultimately, the public -- to monitor the court system.

They say they think the eight-year-old Alexandria courthouse is at the forefront of a trend toward more secrecy in the courts that is characterized by the use of closed hearings, gag orders and anonymous juries to shield identities.

Steven D. Benjamin, president of the Virginia Association of Criminal Defense Lawyers, compared the Alexandria grand jury to a star chamber. The level of seclusion is "contrary to American values," Benjamin said. "It has this aura of an omnipotent government bringing witnesses under lock and key into a secret area of a government building. That's a little creepy."

"We've been seeing an atmosphere of secrecy sort of closing down like a curtain over the justice system," said Lucy Dalglish, executive director of Arlington-based Reporters Committee for Freedom of the Press. She and others who monitor the courts attribute the trend to a public concern about crime, the focus on terrorism cases since the Sept. 11, 2001, attacks and a backlash against such high-profile trials as the O.J. Simpson case.

Prosecutors and court officials argue that Alexandria is a model of discretion that allows the grand jury to do its work while being fair to witnesses, who may be investigated and never charged.

Paul J. McNulty, the U.S. attorney in Alexandria, declined to comment. Richard Cullen, who was U.S. attorney when the courthouse was designed in the early 1990s, said witnesses should be able to enter and leave the grand jury area without having their identities known.

"There may be cases where there is a public interest in knowing what is going on with an investigation, whether the prosecution is doing its job, and that is legitimate," Cullen said. "But sometimes, you have to balance competing legitimate interests." In some cases, such as those involving violent gangs, the identities of witnesses and grand jurors need to be protected for safety, he said.

Federal grand juries consist of 23 randomly chosen registered voters who hear evidence and decide whether to issue indictments. Federal rules prohibit prosecutors and grand jurors from discussing the proceedings. But witnesses are free to speak, and reporters traditionally have conducted "grand jury stakeouts" to see who comes in and out.

In Alexandria, grand jurors have indicted such high-profile defendants as Zacarias Moussaoui, an alleged Sept. 11 conspirator, and convicted spy Robert P. Hanssen.

A quest for secrecy was behind the decision to conceal the grand jury area under the staircase and the rest of the second floor at the Alexandria courthouse. Howard Melton, the building's principal designer, attributed the design to the desire of the U.S. attorney's office "to get witnesses in front of the grand jury out of the eyes of the public."

Melton, who said the layout was appropriate, said he knew of federal guidelines when the courthouse was designed but recalled none governing the grand jury area. Federal officials said that guidelines took effect in 1991 but that those pertaining to grand juries have not changed.

"Obviously, they didn't follow their own guidelines and they let the prosecutors specify their own design," said Don Hardenbergh, a Williamsburg-based courthouse design consultant who wrote a design guide for courts. "The grand jury area is not accessible by the public at all."

Benjamin said witnesses could feel pressured to testify in favor of the government, the same way a suspect might feel compelled to confess under questioning in a police station.

"The whole idea behind grand jury secrecy is to permit complete honesty, but you can make something so intimidating and so dominated by the government presence that you lose that neutrality," he said.

Edward A. Adams, spokesman for the Alexandria courthouse, said the layout meets federal guidelines in part because grand jurors enter the 10-story, red-brick building through the front door with the rest of the public. They then go up public staircases or an escalator to the gleaming marble columns of the second floor before they are met by security officers, who take them to the first floor using the special elevator key.

Prosecutors can ferry witnesses to the grand jury area -- or reach it themselves -- through a passageway from their office that goes directly there.

Experts on the court system said the level of secrecy in Alexandria is rare. In an informal survey, the Williamsburg-based National Center for State Courts found that state and local grand juries nationwide meet in secret but not in rooms sealed off from the public.

"I don't want to say that nobody has the same situation as Alexandria, but boy, none that I've heard of,'' said Lorri Montgomery, a spokeswoman for the group.

Dick Carelli, a spokesman for the Administrative Office of the U.S. Courts, said most of the nation's older federal courthouses do not restrict access to grand jury areas.

For example, at the courthouse in the District, witnesses and prosecutors walk through a fully public hallway to get to the restricted grand jury area.

"It seems to have worked well for us here," said Channing Phillips, a spokesman for the U.S. attorney's office in the District. "If we are worried about someone's identity being disclosed, obviously there are ways around that. But usually, that's not an issue or problem.''

Many of the newer federal courthouses, however, do restrict access, Carelli said.

Steven Aftergood, director of the Project on Government Secrecy run by the Federation of American Scientists, said he had never heard of such a cloistered grand jury area.

"The very layout of the building is designed to frustrate public access," Aftergood said. "They've gone beyond secrecy to a kind of meta-secrecy.''