4th Addtional District and Sessions Judge Kaveri Bose convicted Mahato, convener of Police Santrash Birodhi Janasadharaner Committee (People's Committee Against Police Atrocities, Sukhsanti Baske, Sambhu Soren and Sagun Murmu under UAPA.
The judge said that the quantum of punishment would be announced tomorrow.
Public Prosecutor Rajkumar Das pleaded for a sentence of life imprisonment for all four persons who were associated with the Maoist movement in Lalgarh between 2008 and 2011.
Mahato was one of the most recognised faces of the Lalgarh movement. He was arrested in September, 2009.