Five months have passed since a flamboyant county sheriff led a squadron of assault weapon-wielding deputies and television news crews on a raid of a hole-in-the-wall travel services business here, declaring he was hot on the trail of an Arab American businessman who had sold fake IDs to two of the Sept. 11 terrorists.

The raid made international headlines, but not for long. As it turned out, the FBI already had interrogated Mohamed Atriss and had concluded he knew nothing more about the hijackers than he did about thousands of other mostly illegal immigrants who bought official-looking identification documents at his office, located directly across the street from City Hall.

The camera crews departed after Atriss, an Egyptian-born U.S. citizen, surrendered voluntarily and was charged with misdemeanors: 26 counts of conspiracy and simulating identification documents. He pleaded not guilty.

Five months later, the alleged proprietor of a small-time document mill is at the center of what appears to be the only criminal case of its kind in the United States since the Sept. 11, 2001, attacks -- one in which secret evidence has been presented against the defendant. Atriss remains in jail, now on $500,000 bond -- an amount consistent with a murder charge -- but prosecutors will not say why he poses such a serious risk or give him a chance to respond.

Passaic County Superior Court Judge Marilyn C. Clark doubled Atriss's bail in November, based on the secret evidence presented to her in a closed hearing -- without Atriss or his attorney present. In a letter requesting the hearing, senior assistant county prosecutor Steven Brizek said that allowing Atriss access to the information -- consistent with his constitutional right to confront evidence against him -- "might compromise or otherwise harm" the criminal investigation. Brizek also filed a charge of racketeering, a felony comparable to residential burglary in the state criminal code.

Clark, who declined to comment, directed a reporter to a 1973 New Jersey Supreme Court ruling that she cites as precedent for the secret hearing. The ruling, State v. Campisi, upheld a bail proceeding in which a judge took into account secret evidence implicating a murder defendant in other organized crime killings then under investigation, for which he later was charged. It also detailed his alleged plan to flee.

"Some people are saying this is extraordinary, but there are circumstances under which there's a justification to deviate from rules of general application," Brizek said.

Atriss's new attorney, Miles Feinstein, said he plans an emergency appeal, saying the secret proceeding had violated Atriss's rights to due process, equal protection and the assistance of counsel. "This an affront to the presumption and assumption of innocence," he said. Feinstein recently joined the case. Atriss's first attorney, Hassen Abdellah, had said he would file an appeal but did not.

Leaders in Paterson's large Muslim community said the secrecy measures are more extreme than the ones the Bush administration has imposed on immigration detention hearings.

"At least in immigration court, my client and I were able to sit in and listen to the substance of the evidence, and I can ask questions and cross-examine," said Sohail Mohammed, an attorney and general counsel of the American Muslim Union. "I'm saying to myself, 'Now they're moving from immigrants to citizens. What is next?' "

In the late 1990s, secret evidence was used in a number of high-profile immigration cases to detain non-citizens of Arab descent on suspicion of terrorism. Judges ultimately ruled the information unreliable; the source in one case was the suspect's estranged wife. And the suspects were released, but only after long detentions, in one case 3 1/2 years.

But a federal appeals court ruled Tuesday that the government can freeze the assets of a U.S.-based global Islamic charity without providing evidence of a suspected terrorist link to defense lawyers. The court said the USA Patriot Act, enacted after the Sept. 11, 2001, terrorist attacks, provides the authority for the government's action.

But other than Atriss's case, civil liberties advocates said they know of no criminal case in the country since the Sept. 11 terrorist attacks in which secret evidence has been allowed. "It's the most basic constitutional issue: the right not to have your freedom constrained without being able to see the evidence that justifies it," said David D. Cole, a law professor at Georgetown University.

Tim Edgar, legislative counsel for the American Civil Liberties Union, pointed out that prosecutors can use classified information in federal criminal cases only if they give defendants a summary detailed enough to allow them to contest the evidence, as guaranteed in the 1980 federal Classified Information Procedures Act.

"A state can provide more protection than the federal government, but it certainly can't provide less protection," he said.

Exactly what information Passaic County presented in the hearing remains a mystery. At Atriss's first bail hearing in August, then-prosecutor Marilyn Zdobinski requested and won a bail of $250,000 after alluding to "ongoing investigations with regard to this defendant's connections to known terrorists." Federal law enforcement officials expressed surprise at the time, saying they were satisfied Atriss did not know the Sept. 11 terrorists or their plans.

Zdobinski argued that Atriss had ample resources with which to flee. She said police had found records of $29,000 he had wired to Arab National Bank in Mecca, Saudi Arabia, adding that he could create his own travel documents, for any identity.

Prosecutor Brizek declined to say whether his office still suspects Atriss of terrorist connections. "To get into the nature of the information would render a nullity the proceeding held out of the presence of the defendant and the public," he said.

But speaking of the Sept. 11 attacks, he added, "It would be folly not to incorporate one's experience with that event into how one views the world and how one should deal with problems that might have impact on our safety and well-being."

Federal and state law enforcement authorities said they have no idea what evidence Passaic County authorities are guarding, but they emphasized that if it relates to terrorism, it should be shared with the FBI and state terrorism investigators.

Complaints against Atriss, who has not been indicted, charge him with making fake international driver's licenses and New Jersey state identification cards, and selling them for more than $100. Neither is an official government document (the American Automobile Association provides international driver's licenses for $10), but Atriss told unsuspecting immigrants that they were, Passaic officials said.

Former defense attorney Abdellah said Atriss's business, All Services Plus, translated immigration and other documents into English, which Atriss would then use to create "international ID cards." They carried a disclaimer noting they were not official identifications, Abdellah said. Atriss, 46, had owned various businesses since at least 1995, according to New Jersey records, including a failed Dunkin' Donuts venture for which the records show him tens of thousands of dollars in debt. Prosecutors said he had not filed federal tax returns for seven years.

According to a Sheriff's Department affidavit, which quotes FBI agents, Atriss provided IDs to two of the Sept. 11 hijackers: Abdulaziz Alomari, who was on the first plane that struck the World Trade Center, and Khalid Almihdhar, who was on the plane that crashed into the Pentagon.

Federal authorities last summer denounced the raid of Atriss's offices by Passaic County Sheriff Jerry Speziale, saying it interfered with their own investigation. They declined to go into detail, but an acquaintance of Atriss's said in an interview that the businessman had agreed to alert the FBI to suspicious applicants seeking identification documents.

The sheriff is no stranger to flamboyance, having made a practice of bringing reporters along on raids that at times produced only minor charges. A former New York City narcotics officer, he has written a book about his undercover days and is trying to have it made into a movie.

Several defense attorneys expressed surprise that Clark, 51, was the jurist who approved the extraordinary secrecy. A former prosecutor, Passaic County's first female Superior Court judge and now chief of the court's criminal division, she is known for careful and detail-oriented decisions.

Clark has preserved a record of the secret hearing for review by higher courts if Atriss appeals.

Staff researcher Julie Tate contributed to this report.

Mohamed Atriss has been in jail for five months without being indicted.