"He passed away on Thursday evening due to cardiac arrest," a family member confirmed.
Geelani, who used to teach Arabic at Delhi University's Zakir Hussain College, is survived by his wife and two daughters.
He was also charged with sedition in 2016, after he had organised an event against the hanging of Parliament attack convict Afzal Guru, days after a similar event at Jawaharlal Nehru University had sparked controversy over alleged anti-national slogans that led to the arrest of student leader Kanhaiya Kumar and two others.
Geelani was arrested in connection with the Parliament attack case but was acquitted for 'need of evidence' by the Delhi high court in October 2003, a decision upheld by the Supreme Court in August 2005.
Though the apex court had upheld the high court decision, it had remained 'suspicious of his role'.
Geelani's counsel, noted lawyer Ram Jethmalani, had argued that the SC's 'unfortunate observations, even while acquitting him for want of evidence, were seriously affecting both his career and social life' but the court had rejected his plea.
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