Should you leave your car unlocked to deter thieves? Mechanics, police, insurance weigh in after smash-and-grab thefts

Over the last few days there has been a rash of smash and grab thefts across Milwaukee and the suburbs -- windows broken and cars rifled through has some asking whether keeping the car unlocked will keep thieves from damaging your car.

Esurance, Nationwide, American Family, Allstate are just a few insurance providers CBS 58 checked with that recommend locking your doors to deter a thief.

"That's a huge debate in the community, and the reality is, it doesn't matter," said Elijah Corona, shop owner at The Family Mechanic, LLC.

For three years now, The Family Mechanic in Bay View has been helping neighbors fix their car windows after a break in -- and they're replacing a lot of them; anywhere between two to five a day.

The shop only charges for the cost of the window, making no profit.

"Over the years, it's progressed quite a bit," said Corona.

He says right now it's the worst he's ever seen, and the problem is spreading. on Thursday, Whitefish Bay Police says seven unlocked cars were rifled through.

Believe it or not, the concept is getting popular: if you take out all valuables and leave your car unlocked, maybe thieves won't smash your window.

But Corona says half of the customers that come in with broken windows did leave their car unlocked.

"They're like, 'We don't know why we got hit. The doors were unlocked.' The other responses have been, 'Our doors are unlocked, they break the windows, and don't even go through anything.' They're just breaking them to break them," said Corona.

Acting Milwaukee Police Chief Alfonso Morales says he's heard of other tactics -- with roughly the same results.

"They leave a note and say, 'If you want I have $5 on the seat, just don't break a window.' There's been a number of different strategies and some work for some people and some other people can leave a note and they still break a window because they don't see the note," said Chief Morales.

Will leaving your door unlocked burn you with an insurance claim? Almost all comprehensive policies will cover theft, regardless of who is at fault, but read the fine print. Some insurers will deny a claim if they believe you have displayed negligence. The City of Milwaukee has explored an ordinance against leaving an unattended car running with keys inside.