If you have ever used a metal detector you will know they have adjustable sensitivity settings
these machines have been in use for some years now.
they are sophisticated enough to have some sort of memory which would show what levels were detected. This, matched up with the cops own records of how much drugs were found and what action was actually taken, can be collated and by averaging the settings from lots of checks will show a value which is an acceptable trade off between false positives and missing large amounts of stuff.
What they are currently trying to in TVP area do is choke off the small-time dealing supply and those who are being blatant about their drug use in public, or committing other crimes as well.
Unfortunately these days there are a load of idiots about in Reading (and many other places) who will do coke, pills and even MDMA, but also get beered up and fight as well. What has happened is that drugs have actually gone mainstream but they aren’t miraculously turning angry bitter young men in to loved up ravers…
