Below is a map a friend of mine created from data available from Baltimore City. It doesn’t contain all homicides in 2015. (It will be updated as soon as all the cases are added to the public database.) It contains homicides up to December 12, 2015. It also contains the locations (black diamonds) of Baltimore Police Department crime cameras. Finally, the police district names were overlaid on the map as well.
It’s easy to think that there is some sort of correlation between the location of cameras and the location of homicides. Some believe that the two data points overlap, so the cameras do not work. Other believe that there is enough of a difference between the location of the cameras and the location of the homicides, so the cameras work (somewhat).
The most reasonable explanation is that the police would not put cameras in safe places. They’re meant to be a deterrent to crime, so they would be put in dangerous areas. So the two sets of points are related to each other, but not in a cause-and-effect way. There are geostatistical ways of looking at this, but it would take a lot of time and effort to do it. For now, you just have the map to inform your opinion.