Additional District and Sessions Judge Surendra Sharma sentenced the trio for murdering former MLA Ashoke Singh of Mashrakh in Bihar's Saran district at his Patna residence in July 1995.
The court had convicted them on May 18, slating May 23 to decide upon the quantum of sentences to them.
The court also slapped a fine of Rs 40,000 on each of three convicts, failing which they will have to undergo an addition jail term of six months.
The trio were also sentenced to 10 years in jail under the Explosives Act with further fine of Rs 20,000 each.
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They were also ordered to two years rigorous imprisonment in connection with another case under IPC.
All the sentences would run concurrently, the court said.
The fourth accused of the case - Kedar Singh was acquitted for lack of evidence.
All the three convicts were taken into custody and sent to Hazaribagh central jail earlier after their conviction.
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