This system has been used in Minneapolis for a while already, and you can view the maps of local gunshots detected by the system.[1] Once in a while, the police have to test the system with police gunshots to calibrate the microphone network.[2] ShotSpotter appears, based on the experience of Minneapolis, to have rather limited usefulness for deterring or prosecuting gunshot crimes. But maybe it aids prevention of crime if police respond to where the gunshots are usually fired with preventive patrols.
Looking at the ShotSpotter reports... this is crazy. I was aware that some shootings happen, but it seems like Minneapolis has 4-5 shootings per week on average. Really depressing idea. 4-5 in a year would probably be a high number for my area (in the UK though).
I came here to post the same links to the Minneapolis PD ShotSpotter page. What's more depressing is that nearly all the shootings are concentrated in a few North Minneapolis neighborhoods. I've hung out in those neighborhoods a lot and I would hear gunshots, see shot-out street lights, etc. especially at night.
Crime is way down in Minneapolis since the mid-1990s though, apparently in 1995 North Minneapolis blocks had the highest rate of violent crime per capita in the nation.
Looking at this table of murders by city internationally, it should be pretty obvious what all these locations have in common...
[1] http://www.minneapolismn.gov/police/statistics/crime-statist...
[2] http://www.startribune.com/local/blogs/224931852.html