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Significance of a Green Tongue in a DUI Arrest

Driving under the influence (DUI) is a criminal offense in Florida.  The offense is proved by impairment of “normal faculties” by drugs or alcohol and/or by an unlawful breath or blood alcohol level of 0.08 or above.  Impairment of normal faculties by alcohol can be determined by testing blood, breath or urine.  But it is much more difficult to determine impairment of normal faculties by marijuana or other drugs.

Currently in Florida, there is no definitive way, like a blood or breath test, to determine marijuana intoxication.  Rather, the only way to determine whether someone’s normal faculties are impaired by marijuana is to assess whether they possess their normal faculties. Normal faculties includes the ability to perform the many mental and physical activities of daily life, such as walking, talking, seeing, hearing, driving and making judgments. Normal faculties are normally assessed in Florida DUI cases via the administration of roadside tests known as field sobriety exercises (FSEs).

In addition to administering FSEs, officers commonly note certain physical observations such as blood shot, watery eyes, pupil dilation, facial flushing, and speech slurring to bolster their conclusion someone’s normal faculties are impaired.  And, in some marijuana-based DUI cases, officers across the United States are alleging that people who’ve recently smoked marijuana have green tongues. In fact, law enforcement officers are instructed to look for a “possible green coating” in one world-wide specialized training program.

Yet there are no credible, peer-reviewed scientific studies supporting the notion using marijuana causes someone’s tongue to turn green. Nonetheless, officers continue to use that observation as one of several signs to justify probable cause and make arrests in marijuana-based DUI cases.

Numerous criminal defense lawyers have expressed doubts about the reliability of the green tongue observation as indicating marijuana consumption. So have courts in two different states.

In 2000, the Washington Court of Appeals upheld a ruling dismissing a traffic stop case where  a state trooper partly used the observation of a green tongue to justify a request to search the vehicle.  Even if a green tongue indicates that someone recently used marijuana, Judge Elaine M. Houghton wrote in the opinion, the absence of other observations and the many innocent explanations for a green tongue reflected a lack of reasonable suspicion to search.  “Although we assume the officer’s assertion to be true for purposes of this opinion, we are nevertheless skeptical as to its accuracy,” Houghton said. “We find no case stating that recent marijuana usage leads to a green tongue.”

Four years later, the Utah Court of Appeals ruled a state trooper arrested a man on a mere hunch based on observations including a green tongue.  There, Judge William A. Thorne Jr. wrote that neither the circumstances of the case nor the trooper’s training and experience supported probable cause to arrest.

At one point, Thorne specifically addressed the arrestee’s alleged green tongue. He noted the state had “presented nothing, no scientific studies and no case law or other authority, to support the reliability of the trooper’s concern.”  Thorne said the court was “troubled” by the trooper’s reliance on a green tongue being “dispositive proof of marijuana use.”

So where did the idea that a green tongue indicates marijuana use originate?  Law enforcement and traffic safety advocates all point to the same two peer-reviewed articles. But neither of those articles concludes marijuana causes someone’s tongue to turn green.

The first article was published in the Journal of the American Optometric Association in 1998. Two of the five authors worked in law enforcement and therefore may have been biased.  The paper states, without citation, that people who’ve recently smoked marijuana “might have a greenish coating” on the back of their tongues.

The second article was published in the Journal of Forensic Sciences in 2017.  There, researchers tested blood samples from people who were suspected of driving under the influence. Police officers documented that 185 drivers had a “coating on the tongue.” When the toxicology came back, 96.2% of them had THC – the chemical in marijuana that cases a high –  in their system.

“The objective signs of red eyes, droopy eyelids, affected speech, coating on the tongue, and the odor of marijuana are very reliable in indicating the presence of THC in the blood,” the study reads. “This is not surprising as they represent the most common symptoms of consuming marijuana.”

But the researchers in that study looked at any coating on the tongue  — not specifically a green one. And, perhaps more importantly, the paper contains the following note on the first page, “Authors all work for The Orange County Crime Laboratory testifying on driving under the influence cases, specifically in regard to marijuana, which represents a possible conflict of interest.”

Thus, despite being unable to cite to any definitive supportive scientific studies, police officers are still being taught to look for a “possible green coating on tongue” in the training to become certified drug-recognition experts.  Specifically, the 2018 Drug Recognition Expert Course instructor guide states that “a greenish coating on the tongue has been documented in two peer-reviewed articles.”  The two peer-reviewed articles, however, are the same unreliable ones from 1998 and 2017 referenced above.

Police don’t solely rely on the observation of a green tongue to make a marijuana-based DUI arrest.  Rather, they typically note other signs possibly indicating impairment including glassy, bloodshot eyes; dilated pupils; and a lack of coordination. But sometimes the claim of a green tongue tips the scales towards an otherwise scientifically unfounded arrest.

If you’ve been arrested for a marijuana-based DUI and you hadn’t been smoking or you smoked several hours before your arrest, you may have grounds to challenge your charges. And, if the officer based part of his assessment you were impaired on you allegedly having a green tongue, you may have additional grounds for challenging your charges.  In that event, the State may be forced to drop your case, or to substantially reduce your charges.  It’s critical you contact a Jacksonville criminal attorney experienced with the nuances of marijuana-based DUI charges to get the best outcome in your case.  Call for your free consultation about how I can give you the best chance of avoiding a marijuana-based DUI conviction in Duval, Clay, Nassau, Baker or St. Johns Counties.