The home ministry's probe body has found no evidence of the police having shot retired Army major Sinha Md Rashed Khan in self-defence, according to sources.
Further, policemen showed professional negligence at different levels after the firing, sources with the probe team said.
The high-level probe body led by Chattogram Additional Divisional Commissioner Md Mizanur Rahman is going to submit the report to the Prime Minister's Office on Monday.
The 80-page report contains a set of 12 recommendations for the authorities concerned, Mizanur told The Business Standard after confirming the time of the report submission.
The report contains details over why the murder was committed and the individuals behind it, he also said.
The probe body talked to 68 people, collected information from the killing scene and visited different spots where Sinha recorded his documentary videos, Mizanur said.
"Whether the investigating agency in the murder case, Rapid Action Battalion, will take our report into cognisance is totally up to them," he remarked.
The home ministry formed a probe body on August 3, three days after Sinha was killed in police custody.
The team was initially scheduled to submit its report within seven working days after the formation, but the schedule was extended several times.
On Wednesday, the probe team interrogated the prime accused of the murder–former officer-in-charge of Teknaf Model Police Station Pradeep Kumar Das.
4 policemen put on four-day fresh remand
Meanwhile, four police members accused in the murder case have been put on four-day remand in the second phase.
The people on remand are Liton Mia, Safanur Karim, Kamal Hossain and Abdullah Al Mamun, associates of Pradeep Kumar Das, Liakat and Nanda Dulal Rakshit in the murder.
The RAB has taken these police members for interrogation from Cox's Bazar District Jail. Md Mokammel Hossen, superintendent of the jail, confirmed this matter.
The investigating officer of the case, RAB Senior ASP Khairul Islam, said the court granted fresh remand for the four for further questioning.
Pradeep, Liakat and Nanda, the three main accused in the case, were also put on four-day remand on the same day, Khairul Islam said.
These four policemen were not remanded as the three main accused were interrogated earlier. The four have been remanded in custody since Sunday. They were taken to hospital for medical examination from the jail, Khairul Islam added.
Among the three main accused, Pradeep was remanded for 15 days in four phases, and Liakat and Nanda were remanded for 14 days in three phases.
Liakat and Nanda gave confessional statements under section 164, but Pradeep did not agree to confess. They are all in jail now.
Eight people, including three members of the APBn, have so far given confessional statements.
Major (retd) Sinha was killed in a police firing at Baharchhara police check-post in Teknaf on Cox's Bazar Marine Drive on July 31.
Sharmin Shahriar Ferdous, Sinha's older sister, filed a case with Teknaf Senior Judicial Magistrate's Court on August 5.