Police have long used the claim that something smells like marijuana as probable cause to justify the search of individuals and vehicles. But the big problem with this so-called smell test is that the reports are entirely unverifiable, and subjective opinion. As well, there are many things that can smell just like marijuana.
Users of the plant have noted it’s similarity to “skunk” scent and other smells. But even when police do find marijuana during searches, this may very well just be random chance rather than the officer’s detection of marijuana smell.
There is a saying that “even a stopped watch is right twice a day,” so if officers claim that they “smell marijuana” and then find nothing, the driver, passenger or pedestrian is often sent on their way. We rarely hear about all of the “false positives” of the police “smell test.” But there is growing evidence that police often simply say that they have detected the smell of marijuana, and if some is found, it is merely a happy coincidence for them.
More often than not, marijuana users seem to take pains to make sure police and others cannot detect their use of the plant. The ability of an individual to detect the presence of marijuana is a very difficult metric to measure. To date, there are absolutely no standardized methods or training, nor any means to verify an officer’s olfactory senses or to score their ability to detect marijuana by smell alone.
Police dogs, by contrast, are trained and tested on the ability to smell marijuana. Police officers, however, have exempted themselves from these methods of training and verification. Perhaps this is precisely so that they can apply this “smell test” to any one and any situation that they please, without any oversight.
Anecdotally speaking, two people exposed to the same smell often differ in their conclusions as to what it is. When it comes to marijuana – which one might presume the officers in question are not often smelling in a setting where the scene has been isolated – this subjectiveness of olfactory detection becomes even greater.
To complicate the matter, the smell of marijuana is itself the olfaction of pure chemicals, specifically terpenes (beta-caryophyllene). This is how police canine trainers teach their dogs to identify the smell. But these terpenes are quite common. There are more than 200 terpenoids in marijuana alone, but many other non-marijuana sources of terpenes are just as common.
The most common terpenoids include limonene, myrcene, alpha-pinene, linalool, beta-caryophyllene, caryophyllene oxide, nerolidol, phytol, and often do not even come from the marijuana plant itself (while giving off similar scents). As a result, many things with these terpenoids, such as skunk scent, marigolds, skunk cabbage, hops, and even various combinations of rotting garbage can create nearly identical smells.
A peer-reviewed journal article, entitled “Marijuana Odor Perception: Studies Modeled From Probable Cause Cases”, published in Law and Human Behavior, (Vol. 28, No. 2, April 2004) explains that “The present findings throw into question, in two specific instances, the validity of observations made by law enforcement officers using the sense of smell to discern the presence of marijuana. Although these instances reflect a very small set of studies with very specific constraints, they do suggest that a blanket acceptance of testimony based upon reported detection of odors for probable cause is questionable and that empirical data to support or refute such testimony in specific cases is sorely needed.”
So what can you do if a cop tells you they “smell marijuana”?
Unfortunately, courts have ruled time and time again that this unscientific measure is valid to provide the officer in question with “probable cause.” But your best bet is still to say that while you have nothing to hide, you do not consent to any searches of your person or vehicle.
Bear in mind that 9 times out of 10, the officer is bluffing, to see how you react.