Detective Branch (DB) of police said Saturday Oishee Rahman in her final confessional statement to the investigators said that she alone killed her father, Special Branch Inspector Mahfuzur Rahman and mother Swapna Begum.
Oishee gave confessional statement under section 164 before a Dhaka court on completion of her five-day remand on Saturday.
Joint Commissioner Monirul Islam said this at a press briefing at the DB headquarters in Dhaka on Saturday.
Police recovered the bodies of Inspector Mahfuzur and his wife from their Chamelibagh residence on Aug 16. Their bodies bore multiple stab wounds, which forensic experts believed, were the work of amateurs.
Monirul said Oishee had sedated her parents on the night of Aug 15 and knifed them to death. Oishee procured 60 pieces sleeping
pills from two-pharmacy shops at Chamelibagh area. Police also identified the two-shop owners. Police will take action also against them. Oishee had fed her parents 60 pills with coffee before killing.
He said the Oxford International School student confined her younger brother to the bathroom as he witnessed her killing their mother.
Oishee had forced their minor domestic help Khadiza Khatun Sumi to assist her, Islam said.
Police believed Oishee and her 'drug addict' friends had committed the murder.
Their maid Khadiza Khatun Sumi also gave her confessional statement before a Dhaka court on Saturday
After recording their confessional statements, a magistrate on Saturday sent Oishee Rahman, daughter of a slain police officer, and their maid Sumi to a juvenile correctional centre.
Oishee and Sumi both were taken to the chamber of Metropolitan Magistrate Anwar Sadat at noon. Anwar Sadat recorded her statement for nearly three hours under section 164 of the CrPC.
Rights bodies had flayed the detention and remanding of Oishee and minor domestic help Khadiza Khatun Sumi saying it violated the Children Act.
Seventeen-year-old Oishee, the prime suspect of the murder case, and two other suspects - Mizanur Rahman Rony, a friend of Oishee, and Khadiza Khatun Sumi, domestic help of the murdered couple, were produced before a Dhaka court after completion of their five-day remand on Saturday.
The details of her statement could not be known immediately. Anwar Sadat, judge of Dhaka Metropolitan Magistrate, recorded the statement of Oishee for nearly three hours starting from 12:30pm.
In a development, another court placed Rony on a fresh five-day remand as Jewel Rana, assistant commissioner of Dhaka Metropolitan Police (DMP) and also the investigation officer of the case, sought a 10-day remand for further investigation of the case.
Asaduzzaman Nur, a metropolitan magistrate, granted the remand to Rony.
Oishee turned herself into Paltan police on August 17, a day after the disclosure of the gruesome murder.
Police arrested Rony and Sumi on the same day. On August 18, a Dhaka court granted five-day remand for Oishee, Rony and Sumi in connection with the killing.
As the Children Act 2013 suggests that anyone below the age of 18 will be considered as minor and cannot be taken on remand for interrogation, Oishee and Sumi had to undergo medical test to determine age.
Meanwhile, Oishee's lawyer filed a petition with the Dhaka Chief Metropolitan Magistrate (CMM) court under the Rights to Information Act, seeking directives on police to stop giving out any kind of information about Oishee to the media.