Updated

The trial of a former Navy sailor on terrorism charges promises to offer a glimpse into how prosecutors say an American serviceman communicated with suspected terrorists over the Internet while on duty and leaked information that could have doomed his own ship.

Prosecutors, defense attorneys and spectators began arriving at the U.S. District Courthouse about an hour before the trial was to begin about 9 a.m. Monday.

Prosecutors allege that Hassan Abu-Jihaad sent details of the location and vulnerabilities of a Navy battle group to suspected terrorism supporters in London.

"I think it's a very important case," said Michael Greenberger, director of the Center for Health and Homeland Security at the University of Maryland. "If we have members of our military who are aggressively passing on secrets to terrorists, that's cause for concern. It's a very aggressive act which would have brought real danger to the United States."

Abu-Jihaad, 32, of Phoenix, has pleaded not guilty to charges he provided material support to terrorists with intent to kill U.S. citizens and disclosed classified information relating to the national defense. If convicted, he faces up to 25 years in prison.

Abu-Jihaad, an American-born Muslim convert formerly known as Paul R. Hall, was a signalman before he received an honorable discharge from the Navy in 2002. He worked in a UPS warehouse in Phoenix and has two young children, friends said.

"He was very opinionated," Miguel Colon, a friend questioned about Abu-Jihaad by FBI agents, said last year. "He would talk about things in regard to the way the Iraq war was going. It was something he disagreed with."

Colon, who met Abu-Jihaad at a mosque in Phoenix, said Abu-Jihaad admired the rebels in Chechnya but he rarely saw his friend angry and had a hard time believing the man whose children played with his children secretly supported terrorists. Colon said Abu-Jihaad was dedicated to his prayers, reading Islamic literature and following rules against drinking.

Abu-Jihaad is charged in the same case as Babar Ahmad, a British computer specialist arrested in 2004 and accused of running Web sites to raise money, appeal for fighters and provide equipment such as gas masks and night vision goggles for terrorists. Ahmad is to be extradited to the U.S.

The Web sites were the premier English-language mouthpiece of terrorists, according to Evan Kohlmann, a terrorism expert and a government witness for the trial.

The investigation was one of the first to target online terrorism financiers after the Sept. 11 attacks and experts have cited Abu-Jihaad's case as an example of how Internet propaganda fuels the radicalization process.

During a search of Ahmad's computers, investigators discovered files containing classified information about the positions of U.S. Navy ships and discussing their susceptibility to attack, according to authorities.

The ship details included the makeup of the Navy battle group, its planned movements and a drawing of the group's formation when it was to pass through the Straits of Hormuz on April 29, 2001.

"According to Navy officials, knowledge of ships' movements, missions and capabilities would be extremely useful in planning a successful terrorist strike," the FBI wrote in an affidavit.

Prosecutors acknowledge they don't have direct proof that Abu-Jihaad leaked details of ship movements.

But Abu-Jihaad exchanged e-mails with Ahmad in 2000 and 2001 while on active duty on the USS Benfold, a guided-missile destroyer that was part of the battle group formation, according to an FBI affidavit. In those e-mails, Abu-Jihaad discussed naval briefings and praised Usama bin Laden and those who attacked the USS Cole in 2000, investigators say.

Abu-Jihaad also purchased videos promoting violent jihad from the group. A judge has allowed prosecutors to play portions of the graphic videos as well as show pages from the group's Web site, which displayed bin Laden's declaration of war against the West.

Prosecutors say the videos and Web pages are important evidence because they must prove not only that Abu-Jihaad leaked the ship details but intended to kill Americans by sending the information to those who promoted terrorism. They say the videos depict martyrdom, explaining why Abu-Jihaad would allow his own ship to be targeted.

Prosecutors also hope to bolster the case by playing intercepted phone calls to show what they say is Abu-Jihaad's coded speech and obsession with security. Authorities said Abu-Jihaad spoke of "hot meals" and "cold meals" in conversations with associates to refer to intelligence that would be useful to strike American military targets.

Abu-Jihaad's attorneys say the statements are irrelevant and the government's case is weak.

But Philip Anthony, chief executive officer of the national jury consulting firm DecisionQuest, said a number of factors weigh against Abu-Jihaad, including his name and a lack of tolerance by jurors for terrorism. Jurors may view the trial as a "Benedict Arnold case" because Abu-Jihaad was in the military, he said.

"Jurors are very willing to follow a circumstantial trail of evidence," Anthony said. "They know a lot of things cannot be seen directly, but if enough facts come together to allow a jury to see a certain action is more likely than not, most jurors will follow that path to conviction."