BANGALORE: Police here plan to conduct a narco-analysis test on the woman serial killer, accused of six murders, as she turned out to be 'a tough nut to crack' and declined to provide details of her complicity in the killings.

The test will be conducted depending on the availability of appointment at Forensic Science Laboratory here, police officials interrogating the 43 year old Mallika, who was arrested earlier this week, said.

Malliaka was accused of luring distressed women to local temples to perform special poojas, later killed them by administering cyanide and stole their jewellery and valuables.

She failed to give satisfactory reply on her activities between the interim period 1999-2007, during which she was suspected to have committed murders, the officials said.