Two men accused of killing 17 young women and children in a suburb of the Indian capital, Delhi, are undergoing tests using a truth drug.
The remains of the children were found hidden in bags
The businessman and his servant will also be subjected to brain mapping tests at a forensic laboratory in the western state of Gujarat.
The two were arrested last week after the remains of the victims were found in a sewer the suburb of Noida.
Several policemen have been sacked for alleged incompetence over the murders.
In a report, the Hindustan Times newspaper says the accused will be injected with sodium pentothal, also known as truth serum, in the hope they will lose their capacity to lie.
The report quotes Dr JM Vyas, director of the laboratory based in Gujarat's capital, Gandhinagar, as saying: "Some individuals reveal much within half an hour while others may take hours."
Officials say the tests may take up to three days and it will be days before the results will be known. The Gandhinagar laboratory is one of the few in the country with the facilities for such tests.
Experts say the narco-analysis tests are not foolproof. Also, they are not admissible in court.
Police control angry crowds outside the house
But police say these tests will help them in their investigation and provide vital clues about how the men's minds work.
The crime has shocked the country and resulted in immense public anger in Noida, especially against the police whom many accuse of negligence and dereliction of duty.
Furious residents have accused police of failing to act over the abductions and murders because many of those reported missing came from impoverished families.
The residents say that as many as 40 children have disappeared in the area over the past two years.
Officials say that those accused of incompetence will be given an opportunity to explain their case, after which a panel will decide on further action.
On Monday, there was rioting around what the press has begun to refer to as the Noida "house of horrors", with police being pelted with stones.