The convicts — Nur Mohammad and Rahima Begum — are on the run.
Chittagong’s Public Safety Tribunal Judge Syeda Hosne Ara pronounced the verdict on Sunday.
Public Prosecutor Jahangir Alam said the couple had been absconding since they secured bail.
The victim is Abul Kalam of Mirsarai Upazila.
Prosecutor Alam said Nur Mohammad had served a jail term in an arson case filed by his elder brother Kalam and that this had motivated him to kill Kalam.
“Nur and his wife Rahima hacked Kalam with sharp weapons when he was returning home after visiting his sister Salma Khatun on Nov 11, 2005.
“Salma saw the couple dump the body in a nearby pond,” the public prosecutor added.
Kalam’s wife Anowara Begum filed a case with police the same day.
Police pressed charges in court against the two on Jan 2, 2006.
The court indicted the couple on May 18, 2010.