District and Sessions Judge Moshiur Rahman Chowdhury passed the verdict in the four-year-old case on Monday.
The convicts who received the death penalty in the case are Prosenjit Gain, husband of the victim, Animesh Gain and Biplob Kanti Mandal.
The court also fined them Tk 45,000 each.
Prosenjit’s brother Sudas Gain has been acquitted in the case.
Among the convicts, Animesh was present in the court to hear the verdict, while Prosenjit and Biplob were on the run.
On Oct 7, 2016, Tumpa was killed in Badurgaccha village in Khulna’s Dumuria Upazila and her body was dumped in the Ghangrail River.
Police recovered her body two days later.
The victim’s brother Samit Mandal filed a case with Dumuria Police Station over the incident.
Police pressed charges against Tumpa’s husband and three others on Nov 25, 2017.