Mohamed al Zawahiri and seven others were cleared of terrorism charges by an Egyptian military court, according to Reuters.
Zawahiri is the brother of Al Qaeda's current leader, Ayman al Zawahiri, who acted as Osama bin Laden's right-hand man for years before bin Laden's death.
The court overturned an earlier conviction of Zawahiri and the others based on charges of "committing terrorist crimes, harming national security, and planning to overthrow the state," lawyer Mamdouh Ismail told Reuters.
The case was 14 years old, and also involved another prominent person, Mohamed al Islambouli, the brother of Khalid al Islambouli, the man who killed Egypt's former president Anwar Sadat, according to Ahram Online.
Ahram Online reported that the case went back to 1998 when 107 suspects from the movement called Islamic Jihad were indicted on terrorism charges, with some being tried in absentia.
More on GlobalPost: Will Egypt's military council turn into a pumpkin?
Zawahiri was a member of Islamic Jihad, which the US describes as a terrorist organization whose "primary goals are to overthrow the Egyptian government and replace it with an Islamic state and attack U.S. and Israeli interest in Egypt and abroad," according to CNN.
Zawahiri will reportedly be released on Tuesday. He was imprisoned in 1999 following extradition from the United Arab Emirates, also in connection with the assassination of Sadat. CNN reported that he was acquitted of the assassination charges, but was later accused of conspiring to overthrow the Egyptian government.
Zawahiri was released last year, after the overthrow of President Hosni Mubarak, but was arrested again by the Supreme Council of the Armed Forces. His nephew, Ahmed al Zawahiri, recalled that Zawahiri's arrest came a day after he spoke to a local paper about the torture he had endured in the Egyptian prisons.
According to AFP, Islamists retaliated against Mubarak's crackdown in the 1980s and 1990s by conducting bombings and attacks, leading to a massacre in Luxor in which more than 60 people, mostly tourists, were killed. Shortly thereafter, militant leaders of the Islamist movement who were in jail published recantations of violence.
More on GlobalPost: Top India CEO warns of slowdown