The study, released Monday by the Urban Institute's Justice Policy Center, found that Baltimore's network of more than 500 cameras has driven down crime in most areas and has given taxpayers a return of as much as $1.50 for every dollar spent on the system.
"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," Nancy La Vigne, the study's lead researcher, said Monday.
Though public safety budgets are being pinched nationwide, Mayor Stephanie Rawlings-Blake said cameras are not a replacement for officers. Baltimore has been adding cameras and working to integrate its citywide system with private networks belonging to hospitals, schools and businesses. Some of the cameras in the city also use technology that triggers a camera to instantly pan toward the sound of a gunshot.
Rawlings-Blake, who appeared on a panel to discuss the study's results, said that while some residents fear that crime cameras create a bad perception in their neighborhood, they generally support cameras. "If there's a problem of crime in a community, they want cameras," she said.
La Vigne praised Baltimore's round-the-clock monitoring but said its privacy policies are "pretty permissive" and allow officers a "lot of leeway to use cameras however they could to support investigations."
Sharon Bradford Franklin, senior counsel for the Constitution Project, challenged the notion that there is no expectation of privacy in a public place and said cities "must build in safeguards up front to ensure your residents' civil liberties." Ultimately, she argued, such policies will make cameras more effective.
The study did not take into account the effectiveness of cameras in prosecuting crimes.
In Chicago, which has the most extensive network of cameras in the country and also saw general crime declines, police can monitor cameras in real time from any desktop computer and, soon, from BlackBerries. That city also uses dashboard cameras in more than 800 police cars, an initiative that does not have support in Baltimore.
Critics note that crime continues to occur in areas monitored by cameras — the study says that crime was reduced, not eradicated. But in terms of bang for the buck, the researchers say, the cameras are a success.
La Vigne's cost-benefit analysis took into account the $8 million spent on cameras during the study period, from 2007 to 2010, and compared it to "averted costs" of the criminal justice system and medical treatment, which she estimated at $12 million. Even using a more conservative analysis, Baltimore "still broke even."
The study determined that four months after cameras were installed in downtown Baltimore, total crime dropped on average by more than 30 incidents a month — a 25 percent decline. She said there was "no evidence" to suggest that crime simply moved to another area.
Around Greenmount Avenue, cameras led to a 10 percent decline in crime, and in the area where the Southern, Southwestern and Western districts converge, crime fell by nearly 35 percent, the study found.
On North Avenue, there was no crime reduction after cameras were installed, however. "We're not sure why," La Vigne said. "We explored different hypotheses, and none of them held up."
In Washington, there was no significant decline for the high-crime areas where cameras were installed. Crime declined overall in the city, but the researchers said there was no indication that it was a result of the cameras. The district also had stronger privacy policies in place than Baltimore and Chicago.
One possible explanation for the disparity in effectiveness, La Vigne said, was that cameras in Baltimore and Chicago are more overt, using blinking blue lights to warn would-be criminals that they are being watched.