The study is a footnote to one of these documents. I will get it to you.
The reality is that people will lie to the police as to whether they have been drinking. On the subject of checking things, I do know that in Quebec, the person I deal with there says that they set up outside such things as rock concerts. They can't make everybody blow, but just the fact that they are there gets people thinking that they aren't sure they want to be one of those suspected of drinking or using drugs.