Phoenix police, in a written report later provided to Mr. Jammal as part of his prosecution, said they had "confirmed" that he "had significant connections to terrorist organizations, including al Qaeda." At some point after that -- prosecutors won't say precisely when -- authorities got a warrant to tap Mr. Jammal's phone and bug his office.

It wasn't an ordinary warrant, the sort routinely authorized by judges in response to applications from police and prosecutors who want to eavesdrop to catch crooks. It was a national-security warrant authorized by the 1978 Foreign Intelligence Surveillance Act, giving authorities much more leeway, and giving wiretap targets fewer rights.

Mr. Jammal, a 36-year-old U.S. citizen born in Lebanon, was never charged with any offense related to terrorism. Yet evidence collected in the FISA eavesdropping played a role in his conviction last April on federal charges focused on fencing stolen baby formula, for which he was sentenced to 10 years in prison.

His case sits on the fine line between the government's responsibility to go all-out to prevent terrorism and its duty to protect the constitutional rights of American citizens accused of crimes. It's a line that has blurred considerably since 9/11 and the 2001 passage of the Patriot Act. It allows authorities to use FISA wiretaps authorized by special courts not only to gather foreign intelligence but to investigate domestic crimes.

Mr. Jammal is appealing, contending that FISA evidence used against him was illegally obtained and crippled his defense. He says the charges against him were trumped up by a government determined to show progress in the war against terror. "It's baby formula of mass destruction here," he said at one pretrial hearing.

With an ordinary warrant for electronic surveillance, authorities must show probable cause that the target committed a crime and limit eavesdropping to conversations about crimes. They must also eventually notify those who were bugged (even if they aren't accused of a crime) and must give defendants complete access to the warrant application, court orders and any actual recordings.

To get a FISA warrant, in contrast, authorities need to persuade a federal judge that there is probable cause that the target is an agent of a foreign power such as a terrorist organization. For U.S. citizens, prosecutors also must show that some crime might be involved. Armed with such a warrant, authorities can eavesdrop on any conversation, regardless of whether it involves a crime. They can withhold from defendants the basis for issuing the warrant, hindering legal challenges to the FISA evidence. And they can restrict defendants' access to the classified transcripts and tapes, which makes it harder for the defense to parry the government's charges or mount its own case....

Even with warrants, critics fear defendants' rights to a fair trial will be eroded, as authorities use intelligence-gathering techniques to pursue criminal cases. "If evidence is procured by methods that wouldn't stand up to the Fourth Amendment, the courts are going to have to stop it," said Rep. Jerrold Nadler of New York, top Democrat on the House Judiciary subcommittee on the Constitution. Cases like Mr. Jammal's "should be challenged in court," he said. "That kind of thing shouldn't happen." [...]

Prior to passage of the Patriot Act, court interpretations required that the "primary" purpose of a FISA warrant had to be gathering foreign intelligence. The Patriot Act, passed in October 2001, broadened the rules so that intelligence gathering need only be a "significant" purpose of FISA wiretapping. Evidence obtained under FISA warrants has been used in a handful of cases involving charges not directly related to terrorism, including at least one immigration proceeding.

Mr. Jammal's case shows how much the legal environment changes when FISA wiretaps enter the picture in criminal cases. His first two court-appointed lawyers stepped down in part because the secret tapes required them to get security clearance. Even with such clearance, however, they wouldn't be able to discuss the tapes with their client. His third lawyer, who did get clearance, was able to review only translated summaries, not transcripts, of some intercepted conversations. At trial, the government played the jury a recording made under the FISA warrant that proved damaging to Mr. Jammal: a rambling 14-minute diatribe in which he sometimes rails against the U.S. government in Arabic, and talks about fleeing to Lebanon if officials came after him for unpaid taxes.