Police departments across the world use “sniffer dogs” to help in searches — for explosives, for people who are lost, for human remains and for narcotics. These dogs are widely understood as important for police investigations. They are often praised by courts for their accuracy and reliability.

In Canada, police officers must have “reasonable and probable grounds” to search a home for evidence of a crime or to search a vehicle for drugs or other evidence during a traffic stop. In a series of cases, including R. v. Kang-Brown and R. v. Chehil, however, the Supreme Court of Canada has applied the lower standard of “reasonable suspicion” to sniffer dog searches.

That’s because sniff searches are considered highly accurate and minimally intrusive to the individual searched.

My recent research challenges both these assumptions. It suggests that the underlying rationale for the use of the reasonable suspicion standard in sniffer dog searches no longer holds.

High rate of false alerts

Despite our persistent belief in the “infallible” dog, empirical studies from around the world suggest that even trained and certified detection dogs have an alarmingly high rate of false alerts.

In 2023, for example,........

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