Gopinath Pillai, who was one of the petitioners in 2004 Ishrat Jahan encounter case, died in a car accident in Cherthala area of Kerala's Alappuzha district.
According to reports, Pillai met with an accident on Wednesday when his car got hit by a truck.
He was rushed to a hospital where he succumbed to his injuries.
Ishrat, a 19-year-old Mumbai based girl along with Gopinath's son Pranesh Pillai, Amjadali Akbarali Rana and Zeeshan Johar were killed in an alleged police encounter on the outskirts of Ahmedabad on June 15, 2004.
The Gujarat Police had claimed they had terror links and had plotted to kill the then Chief Minister Narendra Modi.
Pillai, who believed that his son was innocent, fought lengthy legal battles to bring justice to the victims of the alleged fake encounter.