R. v. A.M., 2008 SCC 19
Click here [3] to link to the full judgment.
(Charter / Search and seizure / Sniffer dogs)
On the principal's invitation, the police brought a sniffer dog into a high school and searched for drugs while students were confined to their classrooms.  The police had no reason to believe drugs were present, and would not have been able to obtain a warrant.  During the search, the sniffer dog reacted to a backpack.  The police searched the backpack, found drugs, and arrested the student who owned the pack.  The Court held that the sniffer dog search and the backpack search were unreasonable searches, and excluded the evidence from trial.
Majority/Partially Concurring/Dissenting/Dissenting: 4/2/2/1