In papers submitted yesterday, prosecutors said a life sentence for Sulaiman Abu Ghaith sends an important deterrent message to would-be terrorists.
Abu Ghaith was convicted in March of charges that included conspiracy to kill Americans and providing support to al-Qaida. Abu Ghaith is a Kuwaiti-born imam who married bin Laden's eldest daughter about five years ago.
He is the highest-ranking al-Qaida figure brought to trial on US soil since the 2001 attacks. Sentencing is set for September 23.