A wing mirror error could be a sign to thieves that a car is easy to be stolen.
Vehicles without wing mirrors folded could indicate it has been left unlocked, the AA and police said.
Convicted car thieves spoke to researchers to say how they look out for expensive cars with wing mirrors sticking out.
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Unlocked cars mean thieves can easily break into a car to steal any valuables left inside.
Former police chief inspector Kevin Floyd, a criminologist at Huddersfield University, interviewed car thieves in prison.
(Image: Getty Images)
He told The Telegraph many of them came from “lazy” motorists failing to lock their cars even when they had valuables.
Kevin said: “With modern cars nowadays, open wing mirrors equate in the thief’s mind with an open door. It’s as simple as that. It’s a green flag. It’s as easy as walking along the street.
“They don’t want to try the doors because they are so sensitive they will set off an alarm but if the mirrors are open, then it’s confirmation the car is unlocked and no alarm will go off.
“They can then sit there, pretend to be the owner and take as long as they want to have a good look around and either nick things or steal the car. It’s an open invitation.”
He added: “The other basic mistake is leaving valuables in the first place because the car owners are lazy.
“It is not just valuables with a financial value but valuables that can be used to commit more theft. For example, people may leave a bunch of house keys and a letter with their address in there.”
Jenny Sims, the National Police Chiefs’ Council’s, echoed Kevin’s comments after car theft surged by 22% from around 90,000 cases to nearly 110,000, according to the Office for National Statistics (ONS).
She said: “Locking your vehicle, even when filling up or parked on your drive, greatly reduces the possibility of it being targeted by an opportunist thief.
“Even if you have locked your vehicle, check you haven’t left any windows or the sunroof open. Vehicles today are by and large more difficult to steal than ever unless the thief can access your key or fob to clone them.”
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