It seems pretty well established that paper currency (e.g. in the US) is commonly contaminated with trace amounts of cocaine or other illegal narcotics. (See Snopes for instance, though I'm happy to have this assumption challenged.) Is this contamination sufficient to attract alerts by drug detection dogs?
Wikipedia says yes: "The drug content is too low for prosecution but not too low to trigger response to drug-sniffing dogs". But their citation is to a newspaper article that makes no mention of money or currency.
This 1998 Slate article says: "In 1994, a U.S. Circuit Court held that ordinary money contains enough cocaine to attract a drug-sniffing dog." They don't give a reference to the case, but I think it might be US v. Florez; however, the court's opinion only seems to say that the defense claimed this was true (note 12), and doesn't seem to come to a conclusion as to whether it actually is. There is also US v $30,060 in US Currency, in which the court found that a dog's alert on currency is not evidence that the possessor is somehow involved with narcotics, partly due to the fact that money is commonly contaminated. But this seems like a somewhat different question and a different standard of proof, and anyway I'm not inclined to consider judges as scientific experts.
On the other hand, the American Society of Canine Trainers says that "currency in circulation does not contain enough narcotic scent for a narcotic detector dog to alert to", and they also cite case law in their favor.
What data actually supports any of these claims? Does currency commonly contain enough narcotics residue to trigger an alert by a typical drug detection dog, at a rate significantly higher than the usual rate of false positives for such dogs?
[I became interested in this claim after it appeared in this travel.SE answer. Thanks RoboKaren, even though you're not a notable source by yourself.]