They're absolutely being used to solve crimes and arrest people. Here's two examples:

https://www.cbsnews.com/atlanta/news/flock-cameras-help-iden...

https://www.wsbradio.com/news/local/cobb-police-credit-new-t...

There's some studies showing support but it's very hard to attribute cause to a crime rate that constantly fluctuates and has a myriad of causes