The trend came to light in the posh southern part of the city where a gambling racket was operating full time but came out clean every time police paid a surprise visit.
Police later received input about CCTV cameras installed around the gamblers' hideout in Vasant Gaon area and planned a secret operation, a senior official said.
But things only got worse as a woman, who allegedly sheltered the gang, confronted the police team and accused them of harassing her, that too by entering the premises of her house, and to support her claims, she had CCTV grabs.
"It has been observed that criminals indulged in sale of illicit liquor, running gambling rackets and selling drugs, have installed CCTV cameras in their houses to keep check on the movements of beat constables of the area.
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"If any beat constable dares to enter the premises forcibly, they would use these CCTV cameras as evidence, alleging them of having gone there to demand money or harassment caused to women living inside the premises," DCP (South) Ishwar Singh said.
The marijuana ring, busted in Sangam Vihar area, was allegedly headed by a 50-year-old woman who had installed CCTV cameras in and around her shanty from where the dealings took place. She wrapped up within seconds every time her informers, who were tasked with monitoring the footage, informed her of police presence, a senior official said.
After south, investigators in other police districts are also now developing intelligence on the same trend in areas under their jurisdiction, he added.