LLRX. com Article on Sniffer Dogs
"Detection or sniffer dogs are used to ferret out illicit and dangerous substances, such as accelerants, explosives, illegal drugs, environmental hazards and other contraband. While these service dogs' abilities are highly touted, the use of an animal's olfactory sense in ascertaining the cause of a fire or locating drugs raises Fourth Amendment, evidentiary and due process issues."The Supreme Court of Canada heard a case in 2008 relating to the use of sniffer dogs to find drugs in an Ontario high school, R. v. A.M.,  1 S.C.R. 569, 2008 SCC 19.
"This article surveys select studies, standards and resources about canine scent detection evidence"
In its authorities section, the ruling cites a number of additional Canadian, American and Australian sources on the reliability of evidence gathered using sniffer dogs as well as on the issue of when the use of sniffer dogs can be considered a reasonable search.