What are the chances that authorities spy people’s devices?

I wanted to figure out whether authorities can potentially, not in terms of whether they are allowed to, spy people’s smartphones activities such as e-amail, whatsapp chats, and so on. I don’t mean the FBi or NSA techniques used to catch dangerous people or whoever is highly harmful to the society, but I mean whether simple police stuff could possibly spy, for example, small drug dealers phones in order to dismantle their plans and so forth.