The convict is Pintu Debnath, 41. The shop’s staff Bapen Bhowmick was given seven years jail sentence and fined Tk 50,000 for his role in the murder.
Bapen will have to serve six more months in jail if he fails to pay the fine.
The court also acquitted accused Abdullah Al Mamun Mollah.
According to the prosecution, jewellery shop owner Prabir Gosh went missing on June 18. Later, Detective Branch of Police arrested Pintu and Bapen from Kalirbazar on July 9.
Following their statement, police recovered the body of Prabir from the septic tank of one Rasedul Islam Thandu Miah in Amlapara area of the city.
Later, Pintu confessed to his crime before the court.
Police pressed charges against Pintu, Bapen and Abdullah on September 10.
After examining the records and 27 witnesses, Narayanganj District and Sessions Judge Anisur Rahman handed down the verdict.