Results were best in Baltimore and Chicago, but not as much in Washington, D.C.
From the Urban Institute press release, authors of the study:
"Between 2007 and 2010, researchers from the Urban Institute's Justice Policy Center studied public surveillance systems in Baltimore, Chicago, and Washington, D.C., to measure the extent of their use, their effects on crime, their other benefits, and their costs.
While results varied by area, surveillance systems in Baltimore and Chicago produced more than enough benefits to justify their costs. No cost-benefit analysis was conducted in Washington, D.C., because the cameras didn't show a statistically significant impact on crime there.
Much of the cameras' success or failure depended on how they were set up and monitored, and how each city balanced privacy with security, said Nancy La Vigne, the study's lead researcher and the director of the Institute's Justice Policy Center.
"Overall, the most effective surveillance systems are those that are monitored by trained staff and have enough cameras to detect crimes in progress and investigate them after the fact," La Vigne observed."