The debate over the effectiveness of sniffer dogs continues to rage. Critics say the sniffer dog program is inefficient, largely ineffective, and dangerous. Advocates say the dogs are a strong crime deterrent and if you don’t want to get in trouble, you simply shouldn’t use drugs.

But amid all the arguments, one thing remains obvious: sniffer dogs detect drugs. Whether they do it at an effective rate remains up in the air, but the fact that having drugs on you is very likely to set off a sniffer dog is just conventional wisdom, right?

Maybe not. According to Big Think‘s Simon Oxenham, the targets sniffer dogs choose may have less to do with the dog’s senses and their training, than their police officer handlers, who may be the ones actually calling the shots.

“I recently spent a full day at a major music festival observing police drugs dogs sniffing around the entrance, while their handlers bundled off festivalgoers into a nearby tent to have their internal orifices examined by policemen with latex gloves,” Oxenham writes.

“I noticed that the Labradors followed procedure perfectly for about the first half hour of the day, sitting purposefully next to suspects.” However, “after half an hour or so”, Oxenham noticed that the dogs spent the rest of the day “casually sniffing festivalgoers’ bottoms”

“I was shocked to see that the dog handlers occasionally and seemingly randomly behaved in the same way when dogs sniffed punters’ bottoms, as when they had sat bolt upright next to a suspect.” This led Oxenham to an intriguing suspicion.

“As I watched, I became increasingly convinced that the dog handlers were the ones covertly selecting their targets, rather than the dogs themselves.” Turns out, there’s research supporting Oxenham’s hypothesis.

Oxenham’s research led him to a groundbreaking 2011 study by Lisa Lit published in the journal Animal Cognition. In the study, researchers tested the efficacy of drugs dogs and their handlers, with some tweaks to the traditional dog training methods.

“Reliable sources have alleged that individuals with interests in drugs dogs have tried to shut down her research.”

First off, there were no drugs in the study. Secondly, the handlers were told that there were drugs hidden in various places inside of a church. The places where drugs were being hidden were labelled by red sheets of paper.

Researchers tricked the handlers into believing they were participating in a genuine drugs study by carrying a box of 12 triple-wrapped half-ounce bags of cannabis past the handlers while they pretended to set up the experiment.

In actuality, the box was never opened inside the church. “Instead of drugs, sausages were placed in some of the various hidden locations around the church. Some of these locations were labelled as containing drugs — indicated by a sheet of red paper,” Oxenham writes.

“While some locations that were labelled as containing drugs contained neither drugs nor sausages. The experiment was double blind; the experimenters were not aware whether a location was a decoy containing a pair of sausages or a decoy containing what the handlers had been led to believe was cannabis.”

Despite no drugs whatsoever being placed in the experiment space, 225 alerts were issued by the 18 handlers and their dogs, every single one of which was, of course, a false alarm. Interestingly, there were more false alarms wherever the red markers told handlers there would be drugs.

Indeed, research shows that some dogs will rely more strongly on human cues than even their own sight and smell when looking for food, even looking for food in an empty bowl that a human is pointing to, rather than a bowl full of food it can see and smell.

Further research suggests dogs are able to interpret human eye contact, head and body orientation, and glances. Oxenham concludes that setting off a sniffer dog may have as much to do with a police officer’s subjective opinion of you as their dog.

Unfortunately, there haven’t been any follow-up studies investigating Lit’s findings since they were published in 2011. According to Psychological Science, reliable sources have alleged that individuals with interests in drugs dogs have tried to shut down her research.

Oxenham ends his article by citing a 2012 study of ecstasy users, which found a minority of users responding to the sight of drug dogs by immediately consuming all of their drugs, putting themselves at risk of overdose.