A three-member Appellate Division bench led by the Chief Justice passed the order rejecting the appeal of the convicts.
Deputy Attorney general Bishwajit Debnath stood for the state.
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According to the case statement, Rakib died after his former employers inserted a high-pressure air pump nozzle into his rectum at a motor workshop on August 3, 2015.
The high air-pressure tore the 12-year-old boy's intestines, rectum and bladder causing profuse internal bleeding in his stomach.
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On November 8, 2015, Khulna Metropolitan Magistrate Court awarded death sentence to the convicts Omar Sharif and his uncle Mintu Khan for the murder.
Each of the convicts was also fined Tk 50,000.
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On April 4, 2017, the HC commuted the death sentence of two convicts to lifetime imprisonment, after the duo appealed challenging the lower court verdict.
Later, they again filed a review appeal with the Appellate Division of Supreme Court challenging the HC order.