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At some point, I read a news report that investigators found out it is actually safer not to light your house when you are not there or when asleep. It mentioned that thieves found very dark places 'creepy' as well (that was the theory), and they would not try to rob the place. At least not as much as better lit places.

I searched for this but can not find it. Do you know of any investigations that support this theory?

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    I'd imagine it's because a dark unknown house is harder to navigate without alerting the neighbors (through flashlight or falling over stuff) – ratchet freak Apr 18 '12 at 23:41
  • Perhaps they want to look in, to see if a room is empty, before they break in. Some houses have shutters (or curtains) on their windows. – ChrisW Apr 19 '12 at 3:07
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    A criminologist I spoke to did make the very strong point that automatic outdoor yard lights are great for thieves, as no-one is alerted when they come on (cats, foxes etc all trigger them) and they light up access very well. His recommendation was to not use them! – Rory Alsop Apr 20 '12 at 10:39
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    Since what one can view through a pane of glass is directly determined by which side is illuminated more intensely, it stands to reason that a brightly lit interior could provide a casual observer (assuming uncovered windows) with a view of some of the internal layout of the residence as well as the presence/location of valuable items. In contrast, a darkened interior would provide a view at best only darkness but more likely a reflection of ambient lighting from the outside similar to the way one-way mirrors work. – Monkey Tuesday Apr 21 '12 at 4:22
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    @Nick: did the police officer give any reason for the claim that nightlights don't help the intruder? I don't find the claim convincing at all! – iconoclast Sep 14 '12 at 18:10
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We have a theoretical explanation of the mechanism for why outdoor nighttime lights are counterproductive for the purpose of reducing crime. Someone breaking into your house needs to see. If your house is lit, that problem is solved. If not, they must use a flashlight (which is more suspicious to you and neighbors) or they must navigate in the dark, with the attendant increased risk for making noise. As the New Yorker notes:

Much so-called security lighting is designed with little thought for how eyes—or criminals—operate. Marcus Felson, a professor at the School of Criminal Justice at Rutgers University, has concluded that lighting is effective in preventing crime mainly if it enables people to notice criminal activity as it’s taking place, and if it doesn’t help criminals to see what they’re doing. Bright, unshielded floodlights—one of the most common types of outdoor security lighting in the country—often fail on both counts, as do all-night lights installed on isolated structures or on parts of buildings that can’t be observed by passersby (such as back doors). A burglar who is forced to use a flashlight, or whose movement triggers a security light controlled by an infrared motion sensor, is much more likely to be spotted than one whose presence is masked by the blinding glare of a poorly placed metal halide “wall pack.”

There is fairly substantial anecdotal evidence that this mechanism does, in fact, pertain to reality:

In the early seventies, the public-school system in San Antonio, Texas, began leaving many of its school buildings, parking lots, and other property dark at night and found that the no-lights policy not only reduced energy costs but also dramatically cut vandalism.

(Source: David Owen's article in the New Yorker)

The same effect of reduced crime following reduced lighting occurred in two cities in northern Sweden:

"The number of thefts and burglary has been halfed since the city was darkened this autumn [2006] because of the well-known dispute with Ekfors Kraft [local energy company]." "- We thought it would be the opposite, says Sören Mukkavaara, police constaple in Övertorneå."

The rest of the comments section has several more references and examples.

Source: Swedish SvD in Bruce Schneier's security blog comments section, original article by way of the Internet Archive (article dated March 1 2007, archived March 3 2007)

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