A special NIA court in Kerala on Thursday sentenced three of the six convicts, belonging to banned Popular Front of India, to life imprisonment in the 2010 sensational case related to chopping right hand off a Kerala college professor.
Special NIA court judge Anil K Bhaskar termed the incident as a "terrorist act".
The right hand of T J Joseph, professor of Newman College in Thodupuzha in Idukki district, was chopped off by activists of radical Islamic outfit Popular Front of India on July 4, 2010.
"The act of the accused is a challenge to the secular fabric of our nation," the court said, adding that the accused tried to establish a parallel religious judicial system which is "absolutely illegal."
The court awarded Sajil, Nasar and Najeeb to a life term after convicting them on Wednesday for offences under the stringent Unlawful Activities (Prevention) Act (UAPA), Indian Penal Code and the Explosive Substances Act in the second phase of the trial in the case.
In the first phase of the trial, 10 persons were convicted for offences under the UAPA and the Explosive Substances Act and the IPC, and three others were found guilty of harbouring the offenders.
Convicting the three, the court noted that the second accused Sajil took part in the attack while the third accused Nasar was the main conspirator in the case, and the fifth accused Najeeb had planned the "terrorist act" but did not take part in it.
Three other convicts Noushad, Kunju and Ayoob were sentenced to three years in prison.
The attack took place when the professor was returning home with his family after attending Sunday mass at a church in Muvattupuzha in Ernakulam district.
The attackers, a group of seven people, pulled the professor out of the vehicle, assaulted him and then the main accused Savad chopped off Joseph's right hand. The main accused is still absconding.
The police officials who initially probed the case said that the accused wanted to kill Joseph for allegedly insulting Islam by putting a question in B Com semester examination at Newman College.