When Is a Search Not a Search?

A New York Times piece this weekend reports on a hand-held device called DrugWipe that can detect minute residual particles of the most common illegal drugs. Schools are apparently attracted to it as a less intrusive way of "screening" students. I have my doubts: Most people know the factoid that a large proportion of the currency in circulation has detectable traces of cocaine; I'd bet little bits of various drugs are pretty common in our environment.

The interesting question is this: We know that a dog sniff doesn't even count as a search under current Fourth Amendment jurisprudence. The idea is that since it's minimally intrusive and only detects the presence or absence of contraband without risking exposure of unrelated personal information, as rifling through someone's drawers might, it doesn't trigger Fourth Amendment scrutiny at all. And if a dog sniff doesn't count as a search, it seems as though, a fortiori, neither does a mere swipe with this device, which sounds even less intrusive than having a big ol' mutt snuffling around your person.

The question then is: What happens when these things become so cheap that they're standard issue for cops, teachers, and possibly others? How long before suspicionless "drug swipes" are a routine part of a normal day?