Shot Spotter is a set of microphones installed on telephone poles around a city that is supposed to allow police to respond rapidly to gun shots. It actually came to mind when I read recently about people in violence-impacted Philadelphia neighborhoods asking the police for more cameras. This article is about Chicago, and is generally critical of the technology on racial justice grounds. It sounds like the system there is perceived as yet another way for the police to harass people. That sounds bad, but I can imagine this being one more piece of evidence useful for prosecuting a violent crime after the fact. I can imagine a combination of video, audio, and eyewitness testimony being pretty persuasive.