The study by the Urban Institute In Washington D.C., looked at cameras in Baltimore, Washington, D.C., and Chicago. It is the only U.S. study on the impact police surveillance cameras have on crime. And, as ABC 7 News reported last year when the study was still underway, the review of police surveillance cameras has mixed results.
Blue light cameras are fixtures in Humboldt Park and West Garfield Park, two neighborhoods that are right next to each other and in the same police district. In Humboldt Park, Urban Institute researchers concluded that crime dropped because of the presence of the cameras. But that's not the case in West Garfield Park.
On Monday, the Urban Institute unveiled its three city police camera study, and there's no clear rationale as to why the cameras seem to work in one neighborhood, and not another.
"Our study is interesting because it suggests that cameras can have a very powerful impact on crime, and a cost beneficial one, but it also suggests cameras don't work in all places and all contexts," Nancy La Vigne, director, Justice Policy Urban Institute said.
Critics contend that the cameras merely move crime down the street and that it's impossible for human eyes to monitor thousands of electronic eyes, so the cameras aren't really being monitored, and, when they are monitored, it's usually for a drug bust or a lucky get.
However, police surveillance video helped solve a murder four years ago. The video doesn't show the crime, but shows a number of young men running. From a freeze frame, police arrested two teenagers who later plead guilty -- one of them just four months ago -- to a gang murder.
The quality of that video led to a second observation in the study: that video can be very valuable, but it doesn't replace witness testimony. The study also acknowledges what many modern day jurors expect: if prosecutors are going to show tape, it better be high quality and show something happening.
"Jurors want strict proof beyond a reasonable doubt that something happened. When you have a camera in a location and it doesn't capture the event, then they have doubts of the event occurring. They want to see it," said Joe Lopez, defense attorney, said.
Often, the picture is not there for jurors because the camera's down the street, or working on a pre-set rotation that has it pointed in another direction as the crime occurs. Another factor: If there is video, it's often grainy and not terribly revealing. That's when prosecutors have to make a judgment call and decide if it's worth showing at all to a jury.
The study concludes that surveillance cameras are a tool in the crime-fighting toolbox, but not a silver bullet.