Twenty-nine suspects went on trial in Spain on Thursday for bombing four crowded Madrid trains on March 11, 2004. Europe's worst terrorist attack was carried out by an international terrorist cell based in Spain, according to prosecutors -- influenced by al-Qaida and motivated by Spanish involvement in the 2003 invasion of Iraq. Seven lead suspects face 191 counts of murder.

The other 22 suspects -– from Morocco, Spain, Algeria, Syria, and Lebanon –- face charges that include collaborating with a terrorist group and handling explosives.

A long international investigation in the run-up to the trial has produced more than 100,000 pages of evidence. At least 50 lawyers are involved, who may call a total of 650 witnesses to the stand. The proceedings on the outskirts of Madrid are expected to last until mid-July and will be broadcast on local TV as well as the Internet. Journalists and victims' families will watch from rooms near the court.

Jesus Abril, father of Oscar, who was killed in the attacks, told AP he wants to know the terrorists' motives. It's clear, he says, that the wounds from March 11 can never be healed -- he just wants closure from the trial, "so we can mourn in peace."

International suspects, international case

Most of the seven lead suspects are Moroccan, though one is Egyptian and another from Syria. The Egyptian Rabei Osman Sayed Ahmed has already been sentenced to 10 years in Italy, where he was arrested in 2004, on charges of terrorist conspiracy. Italian authorities extradited him to Spain in late 2006. "I am the thread behind the Madrid plot," he says in a recording from a bugged Milan house in May 2004, according to documents from the Italian trial. "I wanted to plan it so it would be something unforgettable, including myself because I was ready to blow myself up."

Ahmed's defense lawyer in both trials, Luca D'Auria, says that no direct evidence links Ahmed to the bombings, according to the New York Times. His client, D'Auria claims, is just a braggart. But prosecutors argue that Ahmed is the most important living link in the Madrid plot. Investigators have claimed that he started recruiting for terrorist attacks in Europe shortly after he slipped away from an asylum camp for illegal immigrants in Germany -- two weeks before September 11, 2001.

The man identified as the mastermind of the Madrid bombing, a Tunisian named Sarhane ben Abdelmajid Fakhet, died with six other lead suspects when Spanish police were preparing to raid their Madrid apartment on April 3, 2004. They died in an explosion in the apartment they were hiding in.

The trial should put an end to a still-lingering story that ETA, the Basque separatist group, bombed the Madrid trains. Jose María Aznar's Popular Party lost national elections in a surprise upset by Socialists three days after the bombings because Aznar, who was prime minister at the time, was suspected by Spanish voters of covering up evidence that Islamic extremists were responsible. Spain has since pulled its forces out of Iraq.

It was clear as the trial started that wounds from the attacks were still raw. Laura Jimenez, a 31-year-old who lost her baby in the attacks, and was crippled for life, refused to go before the court as a witness. "Why should I do that?" she said. "To show people that I've been sitting in a wheelchair ever since? People can see that for themselves. I have nothing to say."