@Saffron Steady on there, 007. The risks outweight the positives, and if you "think" that snapping ordinary members of the public, however 'shifty' they might look, should be done from a distance, then you should've said so in the beginning seeing as you're the one who suggested such a bizarre measure against people who still remain innocent of anything except rousing your own suspicions. What you're encouraging is a more intrusive measure than CCTV, without official sanction. It would be against the law and could potentially leave you vulnerable to litigation served by an aggrieved party who objects to being photographed in public by an anxious and/or paranoid pedestrian. How would you react if you saw someone secretly or "serreptitiously" taking pictures of another member of the public who you didn't feel threatened by? One can only assume that you'd think the worst. Sorry, but the risks do outweigh the positives. By quite a lot, in fact.