(AP) The government's expanded spying powers under the USA Patriot Act face an early legal challenge in the case against five people accused of conspiring to help al Qaeda forces fight U.S. troops in Afghanistan.

U.S. District Court Judge Ancer Haggerty was expected to hear arguments Tuesday and Wednesday asking the government to reveal its justification for 36 secret warrants the FBI used to watch and listen to the suspects.

"Civil liberties for the defendants, and all citizens, certainly are at stake here," said Whitney Boise, attorney for defendant Patrice Lumumba Ford.

Last October, federal agents nabbed Ford, Jeffrey Leon Battle, his ex-wife October Martinique Lewis, and brothers Ahmed Ibrahim Bilal and Muhammad Ibrahim Bilal. A sixth suspect, Jordanian native Habis Abdu al Saoub, who is believed to be the group's leader, remains at large.

Attorney General John Ashcroft called it a "defining day" in the fight against terrorism.

Ashcroft called the group — mostly black American converts to Islam — a terrorist cell. The men are accused of attempting to travel to Afghanistan in the fall of 2001 to join the fight against American forces there. They made it as far as China and turned back, court documents say.

Defense attorneys plan to challenge evidence collected under the warrants issued by the ultra-secret Foreign Intelligence Surveillance court, or "spy court," Boise said.

Law enforcement, defense lawyers and legal experts say the case in Portland is farther along than several other potential challenges to the new spying powers under a provision of the Patriot Act.

"To the best of my knowledge, it's the first," said David Sobel of the Washington-based Electronic Privacy Information Center.

David Cole, a law professor at Georgetown University in Washington, D.C., said the case could test the constitutional boundaries of the new snooping authority given the FBI after Sept. 11, 2001.

The question, he says, is whether it's "constitutional for the government to tap a suspect's phone in a criminal investigation, without probable cause of criminal activity. It's a very important case."

Any decision by the judge on the warrants likely will be appealed to the 9th U.S. Circuit Court of Appeals in San Francisco and then to the Supreme Court, Boise said.

The FBI's use of secret warrants mushroomed after Congress passed the Patriot Act in response to the Sept. 11 terrorist attacks.

Secret warrants were first conceived as a legal weapon to fight Cold War espionage, while putting a legal check on domestic spying in the post-Watergate era. The act creating the secret court passed in 1978. The FBI used the warrants to bug foreign embassies in Washington, D.C., and to keep tabs on suspected spies.

The Foreign Intelligence Surveillance Act waived the bread-and-butter legal standard in criminal cases of "probable cause," but said the spy court could only dispatch agents and their high-tech listening devices for purposes of counterintelligence.

The USA Patriot Act expanded the spy court's power.

Before, the law specified that "the purpose" of a secret warrant must be counterintelligence. A provision of the Patriot Act amended that to say, "a significant purpose" must be intelligence gathering.

That left wide open other potential purposes for secret warrants, privacy watchers say.

Both law enforcement and civil liberties groups interpret the change from "the" to "a" as blurring the line between the counterintelligence and criminal work of the FBI in the fight against terrorism.

Charles Mathews, special agent in charge of the FBI in Portland, defended the change.

"What we're facing in addressing counterterrorism is the intertwining of the criminal and intelligence," Mathews said, adding he could not talk specifically about the pending case.

"We're running a number of cases that are very aggressively pursued from both angles, and it seems to be working. And it couldn't have worked without the changes from the Patriot Act, the 'a' and 'the."'

Mathews said the "purpose, the largest aspect" of spy court warrant applications filed by his office remain intelligence gathering, but that after the Patriot Act, the court is also more fully notified of possible criminal use for the evidence.

"It's hard to go to the (Surveillance Act) court and say, 'we're only interested in the intelligence, and nothing else.' That wouldn't make sense. And we don't do that."

Mathews denied the FBI uses secret warrants where the primary purpose is criminal prosecution. "That's just simply not true," he said.

The scope of the government's expanded use of the warrants remains secret. Even statistics about spy court warrants are classified. The last year they are available is 2001, when the court approved 934 applications from around the country.

The FBI started watching the Portland suspects a few weeks after Sept. 11, when a sheriff's deputy in Skamania County, Wash., spotted some of them firing guns for target practice in a gravel pit.

Secret warrants in hand, the FBI, helped by Oregon State Police, the Portland Police Bureau and other agencies, began around-the-clock surveillance by early 2002.