Cox’s Bazar Chief Judicial Magistrate sent Rubel Sharma, constable of Teknaf Police Station, to jail when police produced him before the court at noon.
Khairul Islam, assistant superintendent of police, said police arrested Rubel in connection with his suspected involvement in the murder.
Later, he was shown arrested in the case and produced before the court, he said.
With the arrest of Rubel, 14 police members were arrested in the case.
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.
All the 13 accused, except OC Pradeep Kumar Das, gave confessional statements before court over the tragic murder.
Also read: Sinha Murder: 4 policemen sent to jail after making confessional statement