If you dig deep enough...

I briefly remember this quote from desperate housewives or some other show where they had an opening or closing quote, something along the lines of if a cop follows a car for long enough, he’s bound to find a broken tail light or something (breaks one himself/fabricates a situation because he couldn’t find what he was looking for) anyway, does anyone know the exact quote or any other similar quotes or analogies or whatever they’re called? What are they called anyway?