Police suspect Asif Mohammad had learned the procedure of human body preservation from the Dark Net that he had used for family members allegedly killed by him in Malda four months ago.

An investigator said despite being buried four months back, the bodies dug out of the trenches inside the house were neither emitting stench nor as decomposed as they should have been under the given set of circumstances.

“He may have learned ways of body preservation from the Dark Net,” said an officer.

Police are almost convinced that the 19-year-old had used a heavy dose of sedatives to make his parents, grandmother and sister unconscious after which he had tied them up and buried them inside the trenches.

The police said Asif himself was addicted to strong tranquilisers and suspected to have used the same for overpowering his family members.

On February 28, Asif had allegedly killed parents Jawad Ali, 53,and Ira Bibi, 39, sister Rima Khatun, 16, and grandmother Aleknoor Bewa, 73. His elder brother Arif said an attempt had also been made on his life but he had escaped.

The police found the materials used for building a coffin were kept in Asif’s friends’ home in Malda. “Asif insisted they keep the materials for the coffin like plywood and marble as he told them the family was soon shifting base from Gurutola village to Calcutta,” an officer said.

On Tuesday, both Asif and Arif were taken to their residence to reconstruct the crime scene and Arif’s escape. “The probe is in the right direction even though we cannot disclose all details right away,” said Alok Rajoria, SP, Malda.