The trial into the 2004 Madrid bombings began Thursday, with 29 suspects facing charges for the al Qaeda-related attack that killed 191 rush-hour commuters.
The accused face charges ranging from terrorist murder to stealing dynamite from mines to sell to the bombers, often in exchange for drugs. All 29 have pleaded not guilty.
The trial comes nearly three years after bombs placed in 10 backpacks ripped through four packed commuter trains during rush hour. About 2,000 people were injured, many of whom are still in treatment.
While the bombings were initially blamed on Basque separatists ETA, a lengthy probe concluded the attack was carried out by a homegrown cell of Muslim extremists angry about the then-conservative Spanish government's support for the Iraq war.
The cell was inspired by al Qaeda but had no direct links to it, nor did it receive financing from Osama bin Laden's terrorist organization, Spanish investigators say.
Seven of the defendants face jail terms of 30 years for each of the 191 killings if convicted, and 18 years apiece for 1,820 attempted murders. But under Spanish law the maximum time anyone can serve for a terrorist conviction is 40 years.
Rabei Osman Sayed Ahmed was the first to be led to the stand, accused of being one of the masterminds of the attacks. But he refused to give any evidence.
"Your honour, with all due respect, I do not acknowledge any accusations or charges,'' Osman said in Arabic, through an interpreter. "I am not going to answer any questions, including from my defence attorney.''
When Osman tried to launch into an explanation of his reasons, a judge cut him off and ordered the prosecutor to begin the questioning.
Later, Osman denied being a member of al Qaeda or any other extremist group, and said he knew other alleged members of the Madrid bombing cell only as acquaintances at a mosque.
"I never had any relation to the events which occurred in Madrid,'' he said, adding he condemned the bombings "unconditionally and completely.''
Ahmed is one of four men whom prosecutors have singled out as masterminds. Two of the others will follow him on to the stand; the fourth was one of seven suspects who blew themselves up in an apartment block weeks after the bombs.
Testimony is expected to last more than five months, with about 100 experts and 600 witnesses likely to be called, among them victims in the March 11, 2004, blasts.
The proceedings are being held under tight security at a trade fair pavilion because the premises of the National Court, which handles terrorism cases, were deemed too small. Family members of those killed have a separate room to watch the proceedings, and psychologists are on hand to counsel them.
Eighteen of the suspects watched Thursday's proceedings from a bulletproof chamber, while the other 11, who are out on bail, sat in the main section of the courtroom.
A verdict is expected late October.
