The Hemisphere program is an example, where police surveilled call logs from phone service providers that went back decades. Stingray and dirtboxes can be used to track location of cell phones or gather identifying information of everyone who brought their phone to a protest or encourage your device to use a less secure, older protocol. Of course there’s the NSA’s mass surveillance program. And logs kept by cell towers can tell police when you connected to and disconnected from certain cell towers, providing information on your location. Service providers can also sell your location data to police or install spyware on your phone that activates your microphone even when you believe it’s off. Spyware can also be installed if your phone has software on it with certain classes of security vulnerabilities. And of course if you post a photo or a video taken at an identifiable location on social media the police will be able to know that you were there.