Additional Sessions Judge Kripankar Chakraborty pronounced the judgement in a packed court and also fined Manik Lal Majumder Rs.5,000, Special Public Prosecutor Lutfur Rahman Khadim said.
Khadim told reporters that Majumder, 59, now posted in the police headquarters, was charged with destroying documents in a signature forgery case whose probe he supervised in 2009.
"Majumder destroyed documents from official files while supervising investigations ... against a food department employee," said Khadim.
Majumder's wife fainted in the court room after hearing the judgement, pronounced after a long hearing.
The accused told the court that he has two daughters and a wife to take care of and that he was a victim of a departmental conspiracy.