Local cops won't acknowledge they use it, but it's the worst kept secret in law enforcement. For years, police across the country slipped GPS tracking devices under cars, allowing them virtual surveillance without late night stakeouts.

But then the Supreme Court came along and ruled that police need warrants, throwing the practice into turmoil. A survey of departments around the area revealed little -- experts said of course they use the devices, while the agencies themselves refused to acknowledge it.

But on Wednesday when Baltimore County police announced the arrest of a man in connection with the theft of a bronze boy with kite statue, officers detailed in court documents how they put a GPS device under the suspect's car and tracked him to thefts at four cell phone tower sites.

And yes, police said they obtained a warrant.

Here's what police tracked:

•Copper wire and metal grounding plate worth $2,000 reported stolen from land leased by BGE on Old Court Road in Woodstock on Feb. 29. Honda Civic tracked to that location at 3:30 p.m. and then at Maryland Recycle Co. in Owings Mills at 4:49 p.m. Receipt shows sale of metal for $150.80.

•Copper and metal grounding plate worth $1,500 reported stolen from cellphone tower on Miller Road in Parkton on March 1. Honda Civic reported at location at 12:28 p.m. and at Maryland Recycle Co. at 2:44 p.m.. Receipt shows sale of metal for $311.50.

•Strips of copper plates and wires worth $1,500 reported stolen from Baltimore County-owned cellphone tower site on Old York Road in Parkton on March 1. Honda Civic reported at location at 1:36 p.m. and at Maryland Recycle Co. at 2:44 p.m. Receipt shows sale of metal for $311.30.

•Wires and metal grounding plates worth $9,200 reported stolen from cellphone tower site on Loveton Circle in Sparks, owned by American Towers, on March 4. Honda Civic reported at location at 3:10 p.m. and at Maryland Recycle Co. the next day at 10:05 a.m. Receipt shows sale of metal for $420.35.