they make people feel a little better. Via Schneier on Security, this article:

San Francisco’s 68 controversial anti-crime cameras haven’t deterred criminals from committing assaults, sex offenses or robberies - and they’ve only moved homicides down the block, according to a new report from UC Berkeley.

Researchers found that nonviolent thefts dropped by 22 percent within 100 feet of the cameras, but the devices had no effect on burglaries or car theft. And they’ve had no effect on violent crime.

Mayor Gavin Newsom called the report “conclusively inconclusive” on Thursday but said he still wants to install more cameras around the city because they make residents feel safer.

“When I put the first cameras in, I said, ‘This may only move people around the corner,’ ” he said. “But the community there said, ‘We don’t care, we want our alleyway back.’ No one’s actually had a camera up that they wanted torn down in the community.”

But not all city officials think it’s wise to spend money on public safety measures if the best thing that can be said about them is they have a placebo effect for worried residents.

“In their current configuration they are not useful, and they give people a false sense of security, which I think is bad,” said Police Commissioner Joe Alioto-Veronese. He added that previous studies of security cameras in other parts of the country have also shown that they do not deter violent crime.

The article continues with the findings—such as the effect of the cameras was to move homicides 250 feet away. The homicides still happened, just not so close the cameras.

Here’s a good discussion of the issue (via Schneier) and Schneier has an excellent lengthy comment on the feeling of security vs. the reality of security. That comment begins:

Security is both a feeling and a reality, and they’re different. You can feel secure even though you’re not, and you can be secure even though you don’t feel it. There are two different concepts mapped onto the same word — the English language isn’t working very well for us here — and it can be hard to know which one we’re talking about when we use the word.

There is considerable value in separating out the two concepts: in explaining how the two are different, and understanding when we’re referring to one and when the other. There is value as well in recognizing when the two converge, understanding why they diverge, and knowing how they can be made to converge again.

Read the whole thing.