Surveillance cameras in Washington, D.C., don't lower crime rates, but the footage they capture can be "a powerful tool" during an investigation, a study finds.
The four-year study, released Monday by the Urban Institute, traces the effects of camera surveillance in the District, Baltimore and Chicago.
Results varied between the cities, depending on how surveillance programs were implemented. While crime fell in the Baltimore areas where cameras where installed, that was not the case in Washington, D.C.
"Cameras alone did not appear to have an effect on crime in D.C.," the study says. However, when a camera does capture a crime, "the footage was a powerful tool in investigating and prosecuting the offense."
Part of the reason, a researcher says, is that Baltimore police monitors the camera feeds continuously so they can react when they witness a crime.
"I think the difference in Baltimore is that they have a dedicated staff who monitor the cameras around the clock. They're typically retired offices so they know what to look for," said Nancy la Vigne, a researcher at the institute.
In July 2007, Baltimore police monitored as robbers shot a drug dealer. Police indentified the shooters' tag number, put it out and made an arrest in minutes.
In Washington, any live monitoring takes place in a room at police headquarters, with an official present. Baltimore police can monitor some 500 sites and in Chicago, any officer with a laptop can monitor some 2000 sites.
"We're a little restricted in our ability to monitor the way that Baltimore and Chicago do it, but we still feel that they're very effective," said Assistant Chief Peter Newshom.
Newshom said the camera footage has helped police solve homicides. D.C. police can review camera footage after a crime, download the video to a laptop and search for clues.
The Urban Institute suggests that increasing the number of cameras and monitoring the feeds live makes them more effective in combating crime.