Of course. Every criminal charge ever filed has been based on things that happened in the past (unless some crazy person at some point in history tried filing criminal charges based on things that hadn't yet happened).
Ummm...ok. I imagine paranoia is a not an atypical symptom of drug addiction. Of course, most adult Americans are probably in a number of databases, so I'm not entirely sure what exactly you're concerned about.
Since this is nothing but a hypothetical concern, I'll simply remind you that you have the right to remain silent when being questioned by law enforcement. By the way, unless you have the intention of committing crimes in the future, why would you expect to be questioned by law enforcement?

