Rangia District and Session Judge Dibyajyoti Mahanta handed out the punishment to Mehboob Hussain of 2nd Assam Police Task Force platoon No. 1 and imposed on him a fine of Rs 14,000.
According to the prosecution, Hussain was convicted for shooting dead his platoon commander Kartik Barman on August 4, 1994 with the service revolver of Barman when he was asleep.
Hussain also tried to commit suicide with the same revolver and injured himself seriously but survived after treatment, the prosecution said.
The convict was sent to Nalbari Jail.