WASHINGTON — Researchers at UC Davis set up a simple experiment to test police dogs and their fabled ability to detect drugs. They told 18 police dog handlers they had hidden small amounts of illegal drugs in four rooms of a church.
Over two days of testing, the drug-sniffing dogs alerted their handlers repeatedly and in every room — 225 times in all. And they were twice as likely to alert on spots marked with red construction paper that the handlers had been told would indicate drugs.
But in fact, no drugs were in any of the rooms, suggesting the “handler’s beliefs” and their “hidden cues” may trigger the dog to alert on a target of suspicion, the researchers said.
On Wednesday, the U.S. Supreme Court will revisit the constitutionality of using police dogs to trigger searches of cars and homes in a pair of cases from Florida. The justices will decide whether the 4th Amendment’s ban on “unreasonable searches” requires the police to have more than an alert from a drug-sniffing dog before they open the trunk of a car or enter a home.
Nationwide, dogs are the leading weapon in the government’s war on drugs. Florida alone has more than 1,000 K-9 units, and they were responsible for more than 130,000 arrests last year.
In the past, the high court has given the police a green light to conduct searches whenever a “well-trained narcotics detection dog” gives an alert. No one disputes that canines have an extraordinary ability to detect odors, and they can be invaluable in finding items such as hidden explosives or human remains.
But some experts in animal science are urging the justices to be cautious before allowing police dogs to serve as a substitute for search warrants.
Alerts from drug-detecting dogs “should be viewed with a healthy skepticism,” said Auburn University professor Lawrence J. Myers, who has studied canines for decades. He said some dogs and their handlers were highly reliable, while others were not.
The UC Davis study “got an enormous reaction in the field,” he said, because it showed the handlers, not the dogs, may be responsible for some of the alerts. “This is a major problem, and we’ve known it for a long time. The behavior of the handler affects the behavior of the animal,” he said.
But Florida prosecutors and police dog handlers say that evidence of a dog’s good training and certification should be enough to demonstrate their reliability. “If a dog is tested in a controlled setting, you know if the dog is wrong or right,” said Arthur Daus, a lawyer for the National Police Canine Assn.
Last year, the Chicago Tribune reported on data from several suburban police districts, which found only 44% of the car searches that were triggered by an alert from sniffer dogs resulted in the discovery of drugs or drug paraphernalia in the vehicle.
Police officers usually discount these “false” alerts, suggesting they are probably triggered by “residual odors” in the vehicle. The dog may have detected the odor of marijuana or cocaine that had been kept in the trunk weeks before, they say.
But Myers said experiments in a controlled environment — like the church in the UC Davis study — also found some dogs and their handlers were wrong more often than right in detecting narcotics.
Last year, the Florida Supreme Court said it was not convinced drug-sniffing dogs were always reliable enough to justify searches of cars on the highway. “There is no uniform standard in this state or nationwide for acceptable level of training, testing or certification for drug-detection dogs,” the state justices said. And the “potential for false alerts and for handler error” means that innocent motorists may be subjected to embarrassing searches, they said.
To justify a search that is triggered by a drug-sniffing dog, the police must furnish a trial judge with the canine’s “field performance records, including any unverified alerts,” as well as evidence of its training and certification, the state justices said.
The case to be heard Wednesday began when a police officer went on patrol near Tallahassee with “his K-9 partner Aldo,” a German shepherd. The officer stopped a pickup with an expired tag. The nervous motorist, Clayton Harris, refused to permit a search of his truck.
After Aldo circled the vehicle and alerted next to a door, the officer said he had probable cause to search inside. He found a bag of pseudoephedrine pills, thousands of matches and other ingredients for making methamphetamine.
Harris pleaded no contest to the drug charges, but the state justices ruled the search of his truck was unconstitutional because the police had not furnished objective evidence of Aldo’s reliability.
In a second case, the Florida court overturned the conviction of a Miami man for growing marijuana in his house. An officer had taken a drug-sniffing dog to the man’s front porch, and the alert furnished the probable cause to obtain a search warrant.
However, the Supreme Court agreed to hear appeals from Florida’s attorney general in the cases, Florida vs. Harris and Florida vs. Jardines.
Kenneth Furton, a chemist at Florida International University in Miami, led a group of scientists who studied police dogs. He said it was not good enough to allow police agencies to test their own dogs.
A dog and his handler must be tested on multiple vehicles, and “they need to be correct nine out of 10 times,” he said.