There are really three major issues there. Number one, there has never been a prison that I am aware of anywhere in the world that has been able to be contraband-free, including illicit drugs. Canada does not stand alone in that challenge.
Two, we don't have a good baseline of information. In all of the interventions we do in terms of interdiction, treatment, prevention, harm reduction, etc., we know about certain prevalence or usage rates of drugs based on things like urine analysis, but there is no real baseline. We don't know, really, how much drug use there is.
The third issue is that there are two kinds of drugs. There are the contraband drugs that we think about—the throw-overs, narcotics being smuggled in, etc.—but there is also the diversion of substances that are otherwise legal in the institution. You might remember the comments made about the high use of psychotropic medication. There are lots of drugs already in prisons, so you have the diversion of otherwise legal drugs as well.
That combination of factors makes it pretty much impossible to make a prison drug-free.