The crime of opportunity is a notoriously hard one for which to arrest anybody.

A criminal sees an opportunity, such as an electronic device lying in plain sight on the passenger seat of a car. He tries the door, and it’s unlocked. He takes the device and carries on, with no one the wiser until hours or sometimes even days later.

By the time the victim realizes she has been victimized, there is no way to get a suspect description, and the suspect profile is as wide as the day is long. Almost anybody who walked by the car would have had one of the most powerful motives in the world — greed — and all the opportunity he could want.

It’s much easier to prevent this crime than to investigate it, and law enforcement officers have been consistent in beating the drum: Lock your doors. Leave your valuables out of sight. Better yet, don’t leave them in the car at all.

Yet the opportunity continues to present itself to criminals, who have taken full advantage in recent years in Suffolk and surrounding jurisdictions.

In the last week, law enforcement officers in Isle of Wight County and Suffolk have issued press releases about a rash of thefts from vehicles. But thanks to good police work and at least one observant citizen, seven juveniles were arrested in Suffolk this week and charged with a variety of crimes resulting from thefts from vehicles.

Overnight on Monday, officers saw two male subjects in the 3200 block of Prices Fork Boulevard pulling on door handles and tampering with a vehicle. After a pursuit, they apprehended both suspects.

About the same time early Wednesday morning, an observant neighbor contacted police after seeing several individuals tampering with cars in the 500 block of Kilby Shores Drive. Officers arrived and eventually were able to track down and arrest five juveniles.

Our thanks go out to the observant citizen and the officers who made these arrests.

But there are some lessons in this for our fellow citizens. Tellingly, not a single one of these teenagers lived in Suffolk. They all came to Burbage Grant and Kilby Shores not just from other neighborhoods but from other cities — Portsmouth and Norfolk.

That means the word has gotten out to troublemakers across the region that Suffolk is a good place to come steal from cars. If that isn’t a frightening enough prospect to make you lock your doors, we just don’t know what is.

Yes, car owners everywhere should be able to leave their doors unlocked without getting their possessions stolen. But sadly, that’s not the world we live in. So please lock your doors, for the good of the community.