The Hazaribagh court declared Singh, along with two other persons, guilty of murdering then legislator Ashok Singh. The quantum of punishment for the trio will be announced on May 23.
Prabhunath Singh, the former MP from Maharajganj who is considered close to RJD chief Lalu Prasad, was named accused in the murder case. During investigation, police also found complicity of Prabhunath Singh's relatives Kedar Singh, Ritesh Singh and Sudhir Singh.
The case was transferred to Hazaribagh in Jharkhand from Bihar on the instruction of the Supreme Copurt.
"It was a long battle, but I had full faith in the judiciary and I'm happy that justice has been done", Chandani Singh, wife of Ashok Singh, told journalists. He was a political rival of Prabhunath Singh and had even defeated him once in the assembly elections.
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The police also strongly advise against paying the "ransom" to regain access to your computer if you have been affected. Experts expressed concern that there would be a resurgence in attacks when people return to work.
A bomb blast at the official residence of Ashok Singh in Patna on July 3, 1995, had killed the Janata Dal MLA and a man identified as Anil Kumar Singh.
Prabhunath Singh, who was present in the court at the time of the judgment, was promptly arrested and taken into judicial custody. He was murdered after 90 days of his victory. Ashok was 28 years old when he was killed.
In another tweet, the BJP leader said: "He is same Prabhunath Singh (convicted today in Mla murder case) who reached fst in Lalu's support 2 days back.".