Slain Al-Qaeda leader Osama bin Laden's son-in-law Sulaiman Abu Ghayth was on Tuesday sentenced to life in prison for conspiring to kill US nationals and providing material support to terrorists.
Ghayth, 48, a former spokesman for Al-Qaeda at the time of the September 11 terrorist attacks, was arrested overseas in February last year and was found guilty in this year following a three-week jury trial.
He is the highest-ranking Al-Qaeda figure to face trial on US soil since the attacks in 2001.
He was sentenced in Manhattan federal court by US District Judge Lewis Kaplan.
In addition to a prison term of life, Ghayth was ordered to forfeit all foreign and domestic assets derived from and used to commit terrorism against the United States, its citizens and residents and their property.
In 2002, Ghayth was successfully smuggled from Afghanistan into Iran, where he was later arrested with other Al-Qaeda leaders.
"Justice has been served," US Attorney General Eric Holder said.
"This outcome ensures that Sulaiman Abu Ghayth, a senior member of Al-Qaeda and an associate of Osama bin Laden, will never again set foot outside a prison cell...we will never waver, and never relent, in our pursuit of violent extremists."
US Attorney for the Southern District of New York Preet Bharara said Ghayth was the "mouthpiece of murder and menace for Al-Qaeda."
Bharara said hours after the 9/11 attacks, Ghayth was exhorting others to pledge themselves to Al-Qaeda in the cause of murdering more Americans.
According to court documents, immediately after the 9/11 terrorist attacks, bin Laden summoned Ghayth and asked for his assistance, which he agreed to provide.
The next day, Ghayth appeared with Bin Laden, his then deputy Ayman al-Zawahiri and another Al-Qaeda leader and spoke on behalf of the group in a speech that would be disseminated around the world, warning the United States and its allies that "[a] great army is gathering against you" and called upon "the nation of Islam" to do battle against "the Jews, the Christians and the Americans".
After the 9/11 terrorist attacks, Ghayth delivered speeches in which he addressed the then-US Secretary of State and warned that "the storms shall not stop, especially the airplanes storm", and advised Muslims, children, and opponents of the United States "not to board any aircraft and not to live in high rises".