Some police dogs are trained to sniff out drugs, bombs, firearms and even child pornography. But under what circumstances can something that these K-9 officers spot with their noses be used as evidence?

It depends on where it is.

Your home

For a police dog to be used in a search of your home (inside or outside, as long as it’s on your property), officers either need to have your permission or obtain a search warrant. Otherwise, they’re in violation of your Fourth Amendment rights.

Traffic stops

When it comes to a traffic stop, the law is more relaxed. As long as the dog is sniffing only the outside of your vehicle during the stop, a warrant or permission isn’t required.

In a U.S. Supreme Court ruling, the justices said that people don’t have a reasonable expectation of privacy around the exterior of their car. In the ruling, however, they noted that they might have deemed the search illegal if officers “had improperly extended the duration of the stop to enable the dog sniff to occur.”

Public places

You’ve likely seen K-9 officers in airports sniffing luggage – potentially for explosives or drugs. This is legal since the luggage is in a public space. In another ruling, the country’s high court ruled that these are not considered searches by Fourth Amendment standards. Likely, the same would apply if a person and their luggage or other bags were in another public place.

Schools

Students have limited Fourth Amendment rights on school property. Courts have ruled that because children and young people have no reasonable expectation of privacy there, dogs can be used to sniff out drugs.

Courts have noted a compelling need to keep schools drug-free. Further, police and their K-9 officer colleagues are typically invited on to school grounds to search for drugs. Police are not allowed to search students’ personal belongings (like backpacks) unless a dog indicates that drugs or other contraband are inside.

Searches involving drug-sniffing dogs continue to be challenged, and court decisions continue to shape the law around them. If your arrest followed a police search involving a dog (or any police search) that you believe was illegal, it’s imperative that you tell your attorney. They may be able to get whatever evidence was discovered tossed out. That could have a big impact on the case against you.