At least for body cameras, the research I've seen suggests small or no effects on number of incidents: https://nij.ojp.gov/topics/articles/research-body-worn-ca

At least for body cameras, the research I've seen suggests small or no effects on number of incidents: https://nij.ojp.gov/topics/articles/research-body-worn-cameras-and-law-enforcement https://nij.ojp.gov/topics/articles/research-body-worn-camer... The cameras do presumably need to be paired with police departments of prosecutors willing to do anything, which doesn't seem to be guaranteed.