The convicts are - victim’s step brother Swapan Kumar Das, Jahidul Islam, Md Farhad Hossain, Moniruzzaman Bhuiyan, Shayan Miah and Md Monzurul Islam.
Judge Abu Zafar Md Kamruzzaman of Dhaka's Speedy Trial Tribunal-1 delivered the verdict in presence of the convicts.
The court also sentenced them to seven years imprisonment each with fine of 50,000 , in default, to suffer one more year imprisonment, for hiding the bodies of the victims in septic tank.
Bodies of 65-year-old retired high school teacher Anil Chandra Das and his wife, 55-year-old Kalpana Das, were found inside the septic tank of their home in Rasulpur area near the district town.
According to the case statement, victim Anil’s step brother Swapan plotted to kill his brother and sister-in-law for grabbing their properties and murdered them with the help of the others on July 26, 2017, in their house.
The killers put the bodies of the victims in separate sacks and dumped those in the septic tank of their toilet.
Later police recovered the bodies.
Victims' son Nirmal Kumar Das filed a case was with Tangail Police Station over the double murder on July 28, 2017.
Also Read- 4 to die for killing Madrassa student in Khulna
Later, the case was transferred to the Speedy Trial Tribunal-1 of Dhaka from Tangail for quick disposal.
Police pressed charges against the six accused in the case on September 17, 2018,
The court on August 7 last year framed charges against the six accused.
Twenty-seven prosecution witnesses out of 35 gave their depositions in the case.