The more interesting quandry is how to section up the video, provide metadata to mark off what crimes/crime scenes each video snippet is associated with. Do you only retain video from crime scenes that are still within statutes of limitations? What if the officer used force during that encounter, do you purge the video anyway? What if the officer has further issues with excessive force down the road, how do you make sure the video hasn't been deleted? Do you slice and dice the video into chunks for each case? I think there's a lot of interesting questions here. Thus far, departments who have implemented it have chosen to just keep the data indefinitely.