Best thing you can do is be real polite and mention some of your family friends are cops, have your story worked out. Know a few names.
If they think they may have to answer to some of their own they tread a bit more carefully.

You could even say "Ive met a few of your lads before ,nice blokes, I once stopped a robbery occurring up in town"... They are all ears. Im lucky I got my story for them.