A New York jury on Thursday convicted Osama bin Laden aide, Saudi exile Khalid al-Fawwaz, over the 1998 Al-Qaeda bombings of US embassies in East Africa which killed 224 people.
Prosecutors described 52-year-old Fawwaz as one of bin Laden's most trusted lieutenants who conspired with Al-Qaeda across three continents for nearly a decade.
The verdict followed a five-week trial in a US federal court, practically in sight of where the former Twin Towers stood before they were destroyed by Al-Qaeda in the 9/11 attacks.
The jury found him guilty on four counts of conspiracy to kill Americans and destroy property on the third day of deliberations.
His conviction brings to 10 the number of defendants tied to the bombings in Kenya and Tanzania who have been convicted at trial or pled guilty in New York.
Fawwaz now faces life in a US prison when sentenced on May 21. Arrested in London in September 1998, he has already spent 16 years in custody.
Manhattan attorney Preet Bharara welcomed the verdict, saying that the Fawwaz had played "a critical role for Al-Qaeda in its murderous conspiracy against America."
"Fawwaz was one of Osama bin Laden's original and most trusted lieutenants," he said.
Prosecutors said Fawwaz led one of Al-Qaeda's first terror camps in Afghanistan, helped lead a terror cell in Kenya and spent years "helping craft and spread" the group's message from London.
Bharara described him as bin Laden's media advisor in the British capital, where he helped Western journalists interview the Al-Qaeda leader in Afghanistan and disseminated his 1998 fatwa exhorting supporters to kill Americans around the world.
It was that directive that preceded the August 1998 bombings, which killed 224 people and wounded around 5,000 others.
Of stocky build and with a long gray beard, Fawwaz attended his trial in a neatly pressed white tunic and a silk white prayer hat.
Defense lawyer Bobbi Sternheim told the opening of the trial that her client was nothing more than a "calm and serene" man who dedicated his life to peaceful reform in his corrupt homeland.
She delivered a lengthy history lesson about the US-sponsored jihad to expel Soviet troops from Afghanistan in the 1980s and the corruption that he was allegedly determined to end in Saudi Arabia.
She said he had "never" shared the violent views of bin Laden and Al-Qaeda, was never a member of Al-Qaeda and was only interested in peaceful reform in Saudi Arabia.
She said he went to London with his wife on a "honeymoon" and to study business English.
Fawwaz fought a 14-year battle against extradition before being sent to the United States to stand trial.
Two of the other 10 defendants convicted over the 1998 embassy bombings have been jailed for life in the last five months alone.
British hate preacher Abu Hamza, 56, was sentenced in January and bin Laden son-in-law Sulaiman Abu Ghaith, a former Al-Qaeda spokesman, was jailed last September.