If the murderers file a petition against their conviction, I will challenge them in a higher court.'

Prasad, a minister in the Rabri Devi government, was gunned down by heavily armed men inside the premises of the Indira Gandhi Institute of Medical Sciences here on June 13, 1998, when he was taking an evening walk. He was then under judicial custody in connection with a fake degree scam and was undergoing treatment.

Surajbhan Singh, Shukla and Tiwari face several other criminal charges, including those for murder, kidnapping and loot.

Surajbhan Singh was sentenced to life imprisonment last year in the murder of a farmer in Begusarai district. Shukla was also convicted in the 1998 murder of Gopalganj district magistrate G. Krishnaiya.