"Public places. It may sound obvious, but you have little to no privacy when you are in public. When you are in a public place your actions, movements, and conversations are knowingly exposed to the public. That means the police can follow you around in public and observe your activities, see what you are carrying or to whom you are talking, sit next to you or behind you and listen to your conversations — all without a warrant."

From the EFF https://ssd.eff.org/your-computer/govt/privacy