Dulal reiterated his demand at a press conference in Barguna press club on Friday noon. He insisted that Minni was involved in the killing.
In a prepared statement, he said an influential group has been trying to divert the investigation.
Dulal insisted that Minni was the mastermind.
“She conspired to kill my son. Sub-Inspector Asad, Obaidul and Assistant Sub-Inspector Sohel Khan, Nayon Bond and Minni sent my son to jail in a false drugs case on May 11,” he said.
Police arrested Minni on July 16 after a daylong interrogation.
Rifat Sharif, 22, was attacked with sharp weapons near the main gate of Barguna
Government College on July 26. In the footage of the incident, Minni appeared to be trying to protect him during the broad daylight attack.
Police have so far arrested 16 people over the murder. The main accused, Sabbir Ahmed alias Nayon Bond, was killed in a reported gunfight with law enforcers on July 2.
Meanwhile, 15 accused have reportedly confessed to their involvement in the killing.