SIM cards , when inserted into a cellphone, link up the user to the grid of other users. Introduced by companies like ACE and BPL Mobile last year, gangsters soon got hooked onto them, installing in their cellphones and replacing them after every misdemeanor. This made it near impossible for the police to track the users down.

The Ministry of Telecommunication has now made it mandatory for all new subscribers of cellphones as well as for buyers of on-the-spot prepaid cards or packages to provide proof of residence aswell as a photograph. This circular is a victory of sorts for the police force, which had frantically lobbied with the government to make it mandatory to seek details from buyers. ``The SIM card, which costs around Rs 4,000, had become a capital investment of sorts for extortionists, who used them at will,'' said DCP Sunil Paraskar (zone-3). The notice will now act as a deterrent and prevent gangsters from misusing cell phones, added Deputy Commissioner of Police (crime) Param Bir Singh.

A case in point is Matka king Kalyanjibhai Bhagat's nephew Mangal, who was recently nabbed by a special squad attached to Zone-3. He picked up a SIM card, assumed the name of Arun Gawli's key hitman DK and extorted Rs one lakh from a Worli garage owner before being nabbed.

``It was almost like having several phone numbers. Gangsters could pick and choose a card at random for their cellphone,'' said a police official. Gangsters were also guiding shooters to home in on their targets. In many cases, the `watchers' overseeingthe killing led the hitmen to their victims with the aid of cellphones and provided them blow-by-blow details of the victims' movements.

BPL Mobile officials said after the circular was issued, the company has now made it mandatory for buyers to furnish documents like I-T Tax PAN card, photo identity card, arms licence, passport or a driving licence with a photograph. Some police officers, however, point out that gangsters will simply resort to using false identities and bogus documents to buy a card.