NEW YORK, March 26 (Xinhua) -- Osama bin Laden's son-in-law Abu Ghaith has been convicted in New York of conspiring to kill Americans by serving as al Qaeda's spokesman after the Sept. 11 attacks, a spokesperson of the federal court told Xinhua on Wednesday.

The jury returned a guilty verdict on three charges: conspiracy to kill Americans, conspiring to provide support to al Qaeda and providing support to al Qaeda. The charges carry a potential penalty of life in prison.

The 48-year-old Kuwaiti-born preacher is the highest-profile bin Laden adviser to face trial in a U.S. civilian court since the attacks. Bin Laden was killed by U.S. Navy SEALs in a mansion outside the Pakistani capital of Islamabad in May 2011.

Testifying in his own defense during the three-week trial, Abu Ghaith denied that he knew of any plots against Americans or ever became a member of al Qaeda as the U.S. prosecutors charge.

Abu Ghaith is married to bin Laden's eldest daughter Fatima, one of nearly two dozen children bin Laden was believed to have fathered before he was killed. Abu Ghaith was captured in Jordan last year and has been held in New York for the trial.