It might be so in the US or UK or wherever your are from, but in Spain everybody over eighteen is obligated to carry our national id (DNI) or similar. If you don't they have every right to take you "downtown" and verify your identity. I don't see the problem in proving you are who you say you are. Example:
COP: Afternoon sir, We are looking for a known serial killer named xxxx. May I see your ID?
RANDOM PERSON: No, but my name is yyyy, I'm not xxxx.
COP: Ok, thank you sir. Good day.
If you don't see a problem with that, you should go back to your cabin, Unabomber.