Seasoned cannabis consumers are accustomed to fielding assumptions connected to a wide variety of “stoner” stereotypes. Luckily, as cannabis legalization has become more widespread, more research is becoming available and we’re able to debunk some of the cannabis myths of the past  – for example, no, cannabis does not make you lazy. This week, the news cycle has blessed us with a new, almost comically, bad cannabis conjecture. Apparently, consuming marijuana turns the user’s tongue green. 

To be fair, the general mischaracterization of cannabis consumers is pretty harmless, at times these stereotypes are humorous. But what happens when those assumptions are held as fact by those appointed to enforce the law? What happens when these cannabis myths lead to serious consequences? 

One Maryland resident discovered, as she was suspected of driving under the influence of cannabis, that law enforcement continues to rely on this strange, “green tongue phenomenon” indicator to determine if a person is currently intoxicated. The affidavit of probable cause concerning the woman’s subsequent DUI arrest explicitly stated that a “green film” on her tongue was one of the reasons for the suspected intoxication.

But this “green tongue phenomenon” is not contained to a strange piece of evidence in this single DUI case. According to one analysis from the York Daily Record, from coast to coast law enforcement training on controlled substances identifies a green colored tongue as evidence that a person has recently consumed cannabis. In most cases, the green tongue has been used to charge drivers for driving under the influence.  This green tongue phenomenon would baffle the most experienced cannabis consumer, and, frankly, the premise is laughable. However, law enforcement’s continued insistence that a green colored tongue can be used as evidence to charge someone with a crime is troubling considering that there is no evidence to support this phenomenon is real. 

Nationwide, law enforcement officers have the opportunity to become drug recognition experts (DRE), a  title that ensures “a police officer [is] trained to recognize impairment in drivers under the influence of drugs other than, or in addition to, alcohol.” The 2018 DRE training curriculum includes the green tongue warning, with an additional note, “A greenish coating on the tongue has been documented in two peer‐reviewed articles.”  However, neither of the two articles referenced in the curriculum, one from 1998 and the second from 2017, include validation of the green tongue phenomenon and only reference that it may exist. Another unusual note about the 2018 curriculum, is that only three years prior, the 2015 DRE training curriculum conceded that, “there are no known studies that confirm Marijuana causing a green coating on the tongue.” Both of these DRE courses were created after the 1998 study referenced in the 2018 training, and the validity of a decades-old study does not change from year to year. Either legitimate evidence of the green tongue phenomenon exists, or it does not. As citizens, we should expect that those touting the credential of “Drug Recognition Expert” would be basing their evidence on facts, not a strange phenomenon that could easily be proven but continues to be unsubstantiated by any valid, peer reviewed study.

Criminal defense attorney, Steve Graham, also questions the legality of using the green tongue phenomenon as probable cause. In one case, Graham defended a driver who had been charged for driving under the influence of cannabis. In the case, the arresting officer had noticed that the suspect “had raised taste buds on the back of his tongue with a green coating on his tongue,” prior to his arrest. But, when the suspect’s toxicology report results emerged,  they showed no trace of cannabis in his blood. Graham insists, “If courts are allowing this sort of evidence, and the local police academies are not insisting on scientifically-reliable criteria, then drivers are going to be hassled and inconvenienced and falsely arrested and detained and embarrassed on the side of the road.”

The perpetuation of these types of cannabis myths erode trust in the competence of law enforcement agencies, and at worst these assertions lead to wasted law enforcement resources and unjust arrests. As cannabis legalization continues to spread throughout the nation, it is of the utmost importance that law enforcement knows how to interact with law-abiding consumers in a civil fashion.  Research shows that “perceived legitimacy of law enforcement is crucial to effective law enforcement.” Perhaps it is time for officers to evaluate if relying on a junk assertion that cannabis consumers are walking around with green tongues is helping or hurting communities’ ability to trust the judgement of law enforcement. 

Until law enforcement has sufficient technology to determine if a person is currently high, officers may continue to rely on this strange, unproven phenomenon in the absence of concrete evidence. While clinging to this cannabis myth may suit law enforcement, courts are beginning to question whether accepting this phenomenon as evidence is appropriate. In 2004, the Utah Court of Appeals ruled that a state trooper arrested a man on a hunch when he used observations including a green tongue. The Washington Court of Appeals also questioned whether a green tongue establishes probable cause for anything, in one case stating, “Although we assume the officer’s assertion to be true for purposes of this opinion, we are nevertheless skeptical as to its accuracy. We find no case stating that recent cannabis usage leads to a green tongue.

The cannabis consumer likely has little power in creating and editing the Drug Recognition Expert curriculum. Perhaps the best advice for consumers is to avoid those tasty sour apple flavored candies and Monster energy drinks before getting behind the wheel, just in case. However, as consumers we must ask ourselves what other fallacies are included in the “expert” training? How long will law enforcement lean on this embarrassingly obvious falsehood to apprehend cannabis consumers?