The quantum of punishment was announced on Wednesday.
Senior counsel BM Tripathy, representing Lakra and others, said: "I was not expecting such a verdict. We will appeal in High Court now."
According to police, Tiwari, who was in love with Lakra's married daughter, went missing on April 24, 2011. He had left for Ranchi and was abducted by the legislator's men, the same day. Tiwari's father had alleged that his son was abducted by Lakra, as he was opposed to the relationship between Tiwari and his daughter and their decision to marry. His bullet riddled body was recovered three days later on April 27, 2011 from a drain at Karra.
During investigation, the police found that the legislator was behind the abduction and killing of Tiwari. Besides the legislator, his bodyguard, driver and another person were named accused in the case. The court awarded life imprisonment to the four.