They led quiet lives as immigrant businessmen or laborers, raising kids and blending into Spanish society. On Friday, they will go on trial as suspected members of an Al Qaeda (search) cell charged with using their new homeland as a staging ground for the Sept. 11, 2001, attacks.

Twenty-four men — mostly Syrians and Moroccans — will sit on wooden benches in a cramped, bulletproof chamber at a makeshift courtroom as Spain becomes only the second country after Germany to try suspects in the Al Qaeda terrorist assault on the United States.

The trial culminates a lengthy inquiry by Baltasar Garzon (search), Spain's top anti-terrorism magistrate, who began investigating Muslim militants in Spain in the mid-1990s and started arresting Sept. 11 suspects just two months after hijacked jets struck the World Trade Center and the Pentagon.

The lead defendant is Imad Yarkas (search), 42, a Syrian-born Spaniard with a wife and six children. Under the guise of being a small-time merchant importing used cars for resale, Yarkas is alleged to have overseen an Al Qaeda cell that provided logistical cover for Sept. 11 plotters such as Mohamed Atta (search), believed to have piloted one of the jets that struck the World Trade Center.

Two other suspects also are accused specifically of helping plan the attack. They are Moroccan Driss Chebli, 33, who allegedly helped Yarkas arrange a meeting in Spain in July 2001 attended by Atta and Sept. 11 coordinator Ramzi bin al-Shibh (search); and Syrian-born Ghasoub al-Abrash Ghalyoun, 39, who shot detailed video of the World Trade Center and other landmarks in 1997.

The videotapes were eventually passed on to "operative members of Al Qaeda and would become the preliminary information on the attacks against the twin towers," Garzon wrote in a September 2003 indictment against the three men and 32 other suspects, including Al Qaeda leader Usama bin Laden and fugitive Moroccan Amer Azizi. The indictment was later broadened to 41 people.

Garzon has said his investigation showed Muslim militants leading discreet lives operated freely in Spain for years, allegedly recruiting men for terrorist training in Afghanistan, preaching holy war and laundering money for Al Qaeda operations.

Spain was struck by suspected Al Qaeda-linked terrorists in the Madrid train bombings of March 2004, which killed 191 people. This week's trial is expected to lay out legal guidelines for that case as well.

The Spanish cell's alleged financial mastermind is Mohamed Ghaleb Kalaje Zouaydi, a father of five who Garzon said used real estate companies to funnel Al Qaeda money to other countries.

Under Spanish law, terrorism is classified as a crime that can be prosecuted here even if it is alleged to have been committed in another country. Garzon also argues he can go after Al Qaeda because the Sept. 11 plot was hatched in part in Spain.

Yarkas' lawyer, Jacobo Teijelo, insists Spain lacks jurisdiction because proceedings are under way in the United States — against French citizen Zacarias Moussaoui, the only person indicted in America in the Sept. 11 attacks. He has yet to go on trial.

Teijelo said Spanish prosecutors "have no solid evidence of anything" and he found it odd that if Yarkas and his alleged accomplices are in fact Sept. 11 plotters, the United States hasn't sought their extradition. "That is jarring from the point of view of common sense," the lawyer said.

Those standing trial starting Friday are the 24 who are in Spanish custody. The rest of the 41 men indicted are either fugitives or in custody in other countries.

Besides Yarkas and his two alleged accomplices, the defendants are charged with belonging to a terrorist organization, weapons possession or other offenses, but not specific involvement in the Sept. 11 plot. They include Al-Jazeera journalist Tayssir Alouny, who is accused of belonging to Al Qaeda.

The trial is being held under tight security at a trade fair pavilion. The normal venue for such proceedings would be the National Court, but it was considered too small for a trial with so many defendants, lawyers and reporters. The trial is expected to last for up to four months.

Prosecutors have requested jail terms of almost 75,000 years each for Yarkas and the other two Sept. 11 defendants — 25 years for each of the nearly 3,000 people killed in the attack. Under Spanish law, the maximum time they can serve for a terrorism conviction is 40 years.

The other defendants face jail terms ranging from nine to 27 years.