Faced with the absence of eyewitnesses and clinching evidence, the Central Bureau of Investigation (CBI) had considered using an advanced DNA sampling technique to get a breakthrough in the Aarushi Talwar case. But exorbitant cost of the method played a role in thwarting the plan, a CBI official said.
The investigation agency had mulled using the Low Copy Number (LCN) or Touch DNA method to examine the crime scene evidence: a bloodstained handprint, an empty Ballantine scotch bottle, clothes and a golf club.
The cost factor and experts’ opinion that the method is not foolproof made the CBI decide against using it, said the official, who is not authorised to speak to the media.
Aarushi and domestic help Hemraj Banjade were found dead in the family’s Noida house in May 2008. The CBI had suspected the handprint, smeared with Banjade’s blood, belonged to a killer who could have leaned on the wall to break his fall.
The scotch bottle found from the dining table at the Talwars' flat had stains of the two victims' blood, but could yield any forensic evidence: two incomplete fingerprints obtained from it did not match with those of the accused — Aarushi's dentist parents Rajesh and Nupur. Also, they did not match with those of former suspects — medical assistant Krishna Thadarai and domestic helps Rajkumar and Vijay Mandal— who were given a clean chit by a CBI probe team.
The CBI was required to pay £60,000 —around Rs. 42 lakh in 2009-10 — to a British forensic laboratory to access its expertise in using the LCN technique after the regular DNA profiling techniques could not lead the investigation agency to the killer(s).
Used in the UK, Netherlands and New Zealand, the LCN technique can derive DNA trace from even minuscule sample — 3-4 cells — unlike regular methods, the CBI official said.
“The decision to not use it was taken in view of the cost and experts’ opinion that the technique did not give robust results.”
The CBI had sought opinions of foreign forensic authorities — including experts from London’s Scotland Yard — on the merits of using the LCN technique, which is not available in India.
“The Hyderabad-based Centre for DNA Fingerprinting and Diagnostics, and three Scotland Yard experts said the LCN technique was not reliable.
“Altogether 24 out of the 26 fingerprints collected from the crime scene by the Noida police, which had started an investigation before the CBI took over, got destroyed due to the alleged faulty procedures adopted,” the CBI official said.
Aarushi’s body swabs were allegedly switched at Noida district hospital before it was sent to the Centre for DNA Fingerprinting and Diagnostics. Two doctors and their former supervisor at the Noida hospital were interrogated several times on suspicion that they had allegedly aided in the destruction of evidence.