District and Sessions Judge Omprakash Srivastav, which convicted them on October 13, delivered the sentence under Indian Penal Code sections 302/149.
Sections 302/149 state that if an offence be committed by any member of an unlawful assembly, every other member of such assembly shall be guilty of the offence - life term).
The court also found them guilty under various other IPC sections.
The prison sentence will run concurrently.
The convicted are: Saheb Ram Madaia, Jitan Bagchi, Bablu Murmu, Bablu Murmu (two persons of the same name), Jairam Marandi, Raju Murmu, Suresh Murmu, Paisil Hembram, Prem Turi, Edwin Murmu, Tala Hembram Rakesh Turi, Pradhan Murmu, Ranjan Marandi, Nazir Soren and Munsi Murmu.