Under the U.S. Constitution, police officers require a warrant to undertake a search. Exceptions to this principle control the reality of individuals’ unwanted encounters with the police.

Searches without a Warrant

When a police officer searches a person without a warrant, the law presumes that the search violates the Fourth Amendment. A search may comply with the Constitution if certain conditions exist. The central factor in the determination of the search’s legitimacy is, in the first instance, whether the search followed from probable cause to believe that the individual searched has violated one or more criminal laws.

The courts have allowed limited searches in other situations.

When Searches are “Frisks”

Fifty years ago, a police officer suspected that a fellow was about to rob a store. The officer stopped the suspect and patted him down weapons. This encounter, in a case called Terry v. Ohio, led to the Supreme Court’s rule that police can search a person for weapons – if the police have a reasonable suspicion that a crime is in progress or is “afoot”.

In the typical example, a police officer sees someone, stops the individual and pats him down “for officer safety”. No gun is found but there is a bag or other container, in which appears to be an illegal drug.

Two issues arise. First, did the officer have a reasonable suspicion and not a “hunch”? Second, since the officer felt the container or bag, how could the officer confuse that object with a weapon?

The Dog Sniff

The Courts have ruled that drug-sniffing dogs are not conducting searches. They are merely providing police with the basis for a search.

In the typical case, the police stop a car, and the police officer decides that the car’s occupants may have a connection to illegal drugs. The police call the “K-9 Unit”. The police then order the car’s occupants to exit the vehicle but remain at the scene.

If indeed there id nothing but a hunch at that point, the length of the detention will determine whether the police violated the Constitution.