"The four evaluations of CCTV in public transportation systems present conflicting evidence of effectiveness: two found a desirable effect, one found no effect, and one found an undesirable effect on crime," the report said. "For the two effective studies, the use of other interventions make it difficult to say with certainty that CCTV produced the observed crime reductions."
Yet, Rosen and Ofer say, the installation of such systems in the United States is popular with many people because of the widely held impression that it is an effective crime-fighting tool, and because of concerns about terrorism since the attacks of Sept. 11, 2001.
"The government is playing on the public's fears of terrorism," Rosen said.
A study this year by the European Commission of the effect of the 200,000 surveillance cameras in operation in London found that crime has risen 10 percent since 2002.
American law enforcement officials say, though, that even if questions about the effectiveness of CCTV systems as crime prevention tools have not yet been answered, their effectiveness as evidence-gathering tools is not in doubt, said Beau Thurnauer, the Coventry, Conn., police chief and head of the crime prevention panel of the International Association of Chiefs of Police.
The case of Carlie Brucia, the Florida girl whose abduction near a car wash was caught on a surveillance camera, brought that into focus for Americans who saw the tape played over and over on cable TV news.
More recently, on Nov. 7, surveillance cameras in a Corona, Calif., shopping mall parking lot filmed the apparent abduction of a woman, who fled frantically from people in a black Toyota Camry Solara as several people stood by and watched. The film of the woman being grabbed, dragged to the car and put in the trunk was blurry, but police said they hoped to be able to enhance the images to help with their investigation.
What concerns Ofer, Rosen and others is what they say is a lack of regulation concerning surveillance cameras, and their great potential for abuse, both by overzealous police and by those who might turn surveillance into voyeurism.
They say the notion that the only people who have anything to fear from increased surveillance are criminals or political activists are mistaken.
Another British study, done at Hull University, found that one in 10 surveillance cameras was at one time or another used to follow women for voyeuristic ends, and in New York City, a surveillance tape from a public housing project that recorded a black man committing suicide was posted on a racist Web site, allegedly by one of the police officers who was supposed to be monitoring the cameras.
