Illinois v. Caballes, Supreme Court of the United States, Justice Stevens, January 24, 2005 [ruling that a driver stopped for speeding and then subjected to a "dog sniff" that revealed the presence of drugs in a particular location of the vehicle could not invoke the Fourth Amendment to suppress the evidence]. Excerpt:

Accordingly, the use of a well-trained narcotics-detection dog —one that "does not expose noncontraband items that otherwise would remain hidden from public view," Place , 462 U.S., at 707 —during a lawful traffic stop, generally does not implicate legitimate privacy interests. In this case, the dog sniff was performed on the exterior of respondent's car while he was lawfully seized for a traffic violation. Any intrusion on respondent 's privacy expectations does not rise to the level of a constitutionally cognizable infringement.

Read the full text of the opinion here [PDF]. Reported in JURIST's Paper Chase here.