The Fourth Amendment, protects an individual's interest in freedom from unreasonable government intrusions into personal privacy. When a court finds an investigative technique to be a search within the Amendment's meaning, it effectively concludes that Fourth Amendment protection should apply. If the government activity constitutes a search, that activity must be reasonable. If the activity does not amount to a search, however, the government enjoys virtual freedom to conduct that activity as unreasonably as it pleases. For pure investigatory searches, the United States Supreme Court has found that the probable cause requirement strikes the proper balance in defining reasonableness. Unlike searches in other contexts," the Court has refused to apply any standard of suspicion lower than probable cause. This requirement imposes a substantial burden on police officers to gather significant amounts of evidence before conducting a search. As a result of the cost of meeting this high standard of suspicion, the Court has excused certain police activities that intrude minimally on personal property, such as canine sniffs, from the rigors of the Amendment by concluding that these intrusions are not searches.'
Canine sniffs" pose an interesting Fourth Amendment problem because they can reveal the presence of concealed narcotics that other- wise might remain hidden from detection. The sniff constitutes a search because it discloses the contents of an item in which the suspect possesses a reasonable expectation of privacy.' The use of a dog's nose, however, poses less of an intrusion into personal privacy than general rummaging or prying into a physical area because the sniff does not reveal private information about its subject beyond what the dog can detect. Because of the effectiveness and limited scope of intrusiveness, canine sniffs are a valuable tool in the fight against drug trafficking. At the same time, the sniffs limited scope of intrusiveness substantially protects citizens' interests in privacy. By applying a traditional probable cause requirement to sniffs, a court would defeat these attractive features of the canine sniffs because police armed with probable cause could, and presumably would, conduct more indiscriminate searches. With few exceptions, federal courts, which are wed to a strict probable cause requirement for pure investigatory searches, have concluded that canine sniffs do not constitute searches within the meaning of the Fourth Amendment.
Kenneth L. Pollack,
Stretching the "Terry" Doctrine to the Search for Evidence of Crime: Canine Sniffs, State Constitutions, and the Reasonable Suspicion Standard,
47 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vlr/vol47/iss3/5