The legalisation of marijuana in some US states is pushing drug detection dogs into early retirement, as their training in cannabis detection makes it easier for drug dealers to argue police searches were illegal.
Police sniffer dogs react the same way to any drug they are trained to detect. So, if a drug dealer has both cannabis and an illegal drug on them, it is impossible for police to prove whether the dog picked up on the marijuana or the other drug.
If the dog detected only the marijuana, the officer has no grounds to investigate if they are in a state where cannabis is legalised - a loophole illicit drug traffickers are now exploiting.
The law change is first known to have caused issues in 2016, when Massachusetts legalised marijuana and the Quincy Police Department had to shift two of its dogs from drug detection to patrol work, the Associated Press reported.
Lieutenant Bob Gillan, the department’s K-9 Unit Supervisor, said drug traffickers used the dogs' previous training in cannabis detection to raise questions about the legality of searches.
"Usually, when they're delivering their illegal drugs, they will always have marijuana burning in the car. Any defense attorney worth his or her salt will say, 'Well, your dog hit on a legal substance [not the illegal drugs]'," he told the Associated Press.
Don Slavik, executive director of the US Police Canine Association, told the Associated Press retraining dogs wasn't an option.
"Once you train a behaviour in a dog, that never goes away. They don't want any mistakes, so... they want to bring in new dogs."
In Virginia, possessing up to one ounce (28g) of recreational marijuana will become legal on July 1, so the state police are retiring 13 K-9s and training new dogs.
Sheriff Mike Miller of Bedford County, Virginia, told the Associated Press: "We won't use our dogs trained in marijuana because that could be a defense an attorney would raise for a client, to say, 'Which odour did the K-9 alert on - was it marijuana or was it an illegal drug?'"
The estimated cost of buying and training a new drug detection dog can come to as much as US$15,000 (NZ$20,670), the Associated Press reports.
