The four are – ASI Liton Miya, Constables Safanur Karim, Kamal Hossain and Abdullah Al Mamun.
Members of Rapid Action Battalion, the investigating agency, took the four to the court premises around 10:30am.
Later, Senior Judicial Magistrate Delwar Hossain recorded statements of Safanur and Kamal while Senior Judicial Magistrate Tamanna Farah recorded statements of the two others for around five hours.
ASP Khairul Islam, investigation officer of the case, said Rab took the four to their custody on September 6 for interrogation.
“The four have admitted many issues during remand,” he said.
All the 13 accused, except OC Pradeep Kumar Das, gave confessional statements before court over the tragic murder.
Major (retd) Sinha was killed in police firing at Baharchhara police check-post on July 31.
Sharmin Shahriar Ferdous, elder sister of Sinha, filed the case at Teknaf Senior Judicial Magistrate Court, accusing the 13 police members.
Also read: No idea how Sinha murder probe report leaked: Home Minister