Additional District and Sessions' Judge M Ali Ahmed gave the verdict on Masum and Ali Akbar, son of Alauddin, Mojammel, son of Ali Akbar and Aman Ullah, son of Syed Ali.
All of the convicts are residents of Borobatua village, Borua upzila in the district.
The court also acquitted Md Tanveer, son of Ali Akbar, as the prosecution failed to prove him guilty.
According to the prosecution, the convicts hacked Izzat Ali to death over previous on March 8, 2003.
Brother of the deceased filed a case with Borua police station accusing eight people.
Police pressed charge sheet against five people on November 2, 2003.