Not sure really. Our local police were all over Facebook posting about a cannabis raid a few weeks ago in a derelict bank on our High Street. Apparently they'd been "tipped off" by passers by who could smell it as they passed.
So, presumably, none of the police officers who'd also passed by that derelict bank had been able to smell it? Not sure that random members of the public are known to have better sense of smell than police officers??
Or is it just that they don't know how to be proactive anymore? Are they so obsessed by targets etc that they only care about "crimes" that are actually reported and that they're instructed to deal with, and no longer think for themselves about crimes happening around them?
Funny thing, on those same Facebook posts, they asked the public to report any other premises with strong cannabis smells and were absolutely inundated with comments about probably a dozen other places, again, all in main thoroughfares, not the back end of beyond, where police officers would be walking past themselves. One was literally opposite the derelict bank they raided in a derelict shop that they then posted all over Facebook the following week after raiding that one too!
If they were genuinely only interested in the "top", surely they'd have kept quiet about the reports, started observations, and hoped to catch/trace the people involved? But no, it seems that they raided the premises almost as soon as they were reported!
So many comments on Facebook were basically telling the police just to take notice of what was happening around them, take notice of the obvious smell of cannabis plants, etc., and be proactive!
So, no, I think in most of the cases of crimes, etc., the police don't know at all, or they choose to turn a blind eye.