His close aide and lawyer Shamshad Pathan said that Sinha was suffering from lung cancer for the last six to seven months and breathed his last at Sterling Hospital here.
Sinha, a scientist-turned-lawyer, consistently took on the Gujarat government in the cases related to the Godhra train burning incident and its aftermath.
He also played important role in the legal battle surrounding the four cases of fake encounters, involving Sadiq Jamal, Ishrat Jahan, Sohrabuddin Sheikh and Tulsi Prajapati.
An IIT Kanpur alumnus, he initially worked at Physical Research Laboratory (PRL) here.
After getting his law degree in 1989, he started fighting cases for the underprivileged.
His NGO `Jan Sangharsh Manch' took up labour issues, such as low wages of drivers and conductors of city and state transport corporations.
Rights activists and members of legal fraternity paid homage to Sinha at the office of Jan Sangharsh Manch in Paldi area of the city this evening.
He is survived by wife Nirjhari and son Pratik.
His body was donated to Ahmedabad Civil Hospital, as per his wishes.