In the United States it is very common for employers to require random drug tests. I think this is as intrusive as being searched. If the drug tests caused people to not act crazy or the searches stopped theft I could ALMOST understand it, but these intrusions don't do that. Someone who had a fight with their spouse that morning, or got too drunk the night before, will be less likely to act rationally or be fully attentive than someone who smoked some pot the night before. And it is really easy to steal things from work without getting caught even if they do random searches.

I've found that treating employees like respected people does way more to achieve these goals than all the coercive intrusions imaginable.