ALBANY, N.Y. -- After a bloody raid by US military forces on an enemy camp in Rawah, Iraq, on June 11, 2003, a Defense Department report took inventory. Eighty suspected terrorists killed. An enormous weapons cache recovered. And, in what the report called "pocket litter," a notebook with the name and phone number of the imam of a mosque halfway around the world, in Albany.

Prompted by that notebook and records of 14 phone calls between the imam, Yassin M. Aref, and Damascus, the FBI quickly began a sting operation aimed at Aref. Federal agents used an informant with a long history of fraud who spun tales to Aref about a fictitious plot involving shoulder-launched missiles and the assassination of a Pakistani diplomat in New York.

Aref and a friend who owned a pizzeria were convicted of supporting terrorism by agreeing to help launder money for the fake operation, and in March the two men were sentenced to 15 years in prison.

But their case seems far from over, and it has become a centerpiece in the effort to challenge one of the Bush administration's signature espionage programs.

Lawyers for Aref say they have proof that he was subjected to illegal surveillance by the National Security Agency, pointing to a classified order from the trial judge, unusual testimony from an FBI agent, and court documents concerning the calls to Syria.

If they are right, the case may represent the best chance for an appellate ruling about the legality of the NSA program, which monitored the international communications of people in the United States without court approval. Unlike earlier and pending appeals disputing the program, all of them in civil cases, Aref's challenge can draw on the constitutional protections available to criminal defendants.

In the civil cases, appeals courts have confronted significant threshold questions, including whether the plaintiffs have standing to sue.

"There are dodges available in civil cases that just aren't available in criminal cases," said Corey Stoughton, a lawyer with the New York Civil Liberties Union, which has filed supporting briefs in the case. "This case might be able to put this issue to the test."

In a brief filed this month, Aref's lawyers urged the federal appeals court in New York to rule that the program was unlawful and to reverse the convictions.

Last month, the federal appeals court in Cincinnati dismissed one appeal challenging the NSA program, ruling that the plaintiffs did not have standing to sue, and the federal appeals court in San Francisco heard arguments in appeals from two other challenges this month.