When police officers in Texas and around the country suspect that a vehicle they pulled over contains drugs, they often call a K-9 unit to the scene to conduct what is known as an air sniff. Police dogs are trained to alert when they detect the odor of drugs, and the courts have determined that this kind of alert gives police probable cause to perform a more thorough search. However, a study conducted by investigators from a Missouri newspaper reveals that searches conducted after a K-9 unit has alerted fail to lead to drug seizures about half of the time.
The odor of marijuana can linger for days, which means police dogs may alert to drugs that are no longer present. When drugs are discovered, police often find just residual or trace amounts. This creates another problem for researchers as K-9 handlers are not consistent in how they log these minor discoveries. Some record searches that lead to the discovery of minor amounts of drugs as successful while others consider such an outcome to be unsuccessful.
Some judges have questioned the amount of credibility that courts give to police dogs. In the case that gave police the authority to conduct a search after a K-9 alert, Supreme Court Justice David Souter referred to the infallibility of police dogs as a legal fiction. However, such misgivings were not enough to stop the Supreme Court from ruling in 2013 that the way police dogs perform in the field is irrelevant as long as they are certified at least once a year.
The rules police officers must follow during traffic stops are designed to protect the right against unreasonable search and seizure guaranteed by the Fourth Amendment, and experienced criminal defense attorneys may seek to have charges dismissed when they are broken. One such rule deals with K-9 air sniffs. In April 2015, the Supreme Court ruled that delaying traffic stops just to give police dogs time to reach the scene violates the Constitution.