MANHATTAN (CN) - Osama bin Laden's son-in-law, an al-Qaida mouthpiece, conspired to kill Americans and provided material support to the known terrorist group before and after the Sept. 11, 2001, terror attacks, a federal jury ruled Wednesday.
Clad in a black suit, Sulemain Abu Ghaith stood as a clerk for U.S. District Judge Lewis Kaplan read the 18-member jury's verdict, capping off three weeks of testimony in a high-rise courtroom blocks from Ground Zero.
With the verdict, Abu Ghaith becomes the highest-ranking al-Qaida member to be convicted in a civil trial on American soil since the Sept. 11 attacks that killed nearly 3,000. He faces up to life in prison at sentencing on Sept. 8.
The five-man, 13-woman jury - who were not sequestered during the trial - began deliberating late Tuesday, spending roughly four hours to hold Abu Ghaith on all counts.
Abu Ghaith, a Kuwaiti cleric, had testified during his trial that bin Laden called for him specifically to his cave in Afghanistan the day after Sept. 11, and that he reluctantly agreed to make a series of fiery propaganda speeches that praised the terrorists and warned of a "storm of airplanes" that would not abate.
These tapes were shown repeatedly to the jury.
Defense counsel argued that there was not a "drop of evidence" that Abu Ghaith conspired with al-Qaida or bin Laden before or after the 9/11 attacks, and that those incendiary videotapes and audio recordings were merely just posturing and not an indication that he knew anything about any future attacks.
But prosecutors said Abu Ghaith was speaking directly about knowledge of plans for the failed plot by "Shoe Bomber" Richard Reid to blow up a transatlantic flight with a bomb in his shoe.
Abu Ghaith, who married bin Laden's oldest daughter, Fatima, five years ago, was captured in Turkey last year and brought to New York for trial. During that flight, he was interrogated by federal officials.
Though Judge Kaplan usually makes it a point not to thank jurors for doing their civic duty, he did so in this case.
"You've taken the job very seriously and gave both sides a fair chance," Kaplan said.
U.S. Attorney General Eric Holder praised the verdict.
"This verdict is a major milestone in the government's unrelenting efforts to pursue justice against those involved with the September 11 attacks," he said in a statement. "I can imagine no more fitting outcome, and no stronger message to those who would harm our nation and its people: that no amount of distance or time can weaken America's resolve to pursue, capture, and hold them accountable to the fullest extent of the law."
Read the Top 8
Sign up for the Top 8, a roundup of the day's top stories delivered directly to your inbox Monday through Friday.