I think acute withdrawal depends on the circumstances of people's entry. Certainly upon arrest some individuals might well be drug-dependent and would show a variety of withdrawal symptoms from whatever substance they were on. That's one level of dependence, if you will. But if people have been using substances as a way of coping with stress and now find themselves in a hyper-stressful environment, their urge to use is going to be very high. That's part of the pathology of addiction, actually: that you really have one way of coping, which is to use substances.
But on your particular question about the moment of entry and whether people are in withdrawal, usually if people are in acute withdrawal they show demonstrable signs that can be assessed and treated.
I'm not sure what the answer is in terms of the numbers.