The CDC has released a study on the impact of surveillance cameras on taxi driver homicides. The study found that the number of taxi drivers killed was lower in cities where the cabs had cameras in them. The CDC found "a three times lower homicide rate in the cities where taxicabs use security cameras than the control cities and a seven times lower homicide rate when compared to the rates before installation of the cameras."
The study says taxis drivers have one of the highest homicide rates of any occupation (taxicab driver homicide rate was 7.4 per 100,000 drivers, compared to the overall rate of 0.37 per 100,000 workers.) But even then, they weren't working with a lot of data to start with. Most cities had less than a few per year.
Does this study convince you? Do you think you could expect to see a similar drop in any location where cameras are installed?