Even with elaborate and accurate equipment, there are likely to be many legal battles fought over how legitimate the equipment is.

As marijuana becomes legal and regulated in many states, law enforcement is often struggling to keep up with the times. There is definitely a learning curve when something that was illegal suddenly becomes legal, and this is particularly true with marijuana. In fact, determining whether someone is under the influence of cannabis remains a difficult thing to prove in a court of law.

When comparing roadside alcohol testing to marijuana testing, a 2019 Congressional Research Service report concluded, “Based on current knowledge and enforcement capabilities, it is not possible to articulate a similarly simple level or rate of marijuana consumption and a corresponding effect on driving ability.” 

Alcohol is fairly easy to test for, and this makes it easy to enforce drunk driving laws. Using precise agreed upon alcohol levels using accurate testing tools have made it straightforward for citizens to follow the law and simple for police to enforce it. Cannabis, however, is already proving to be a far more complicated substance to test for. It is so complicated that the Federal Government plans to spend $1.4 million to study how marijuana compounds concentrate on breathing in hopes of creating a reliable breathalyzer test. 

This study, known as “Breath Measurements of Acute Cannabis Use (BRACE): towards Reliable Determination of Recent Use,” is the latest effort by the government to quantify levels of marijuana impairment. One new approach this study aims to take is to accurately measure cannabis on the breath. “To resolve the challenges of determining recent cannabis use from a single breath sample, we propose a paradigm shift: two breath samples spaced a short interval apart.” The idea here is that the change, ( great or small) in the two measurements, could accurately determine how recently cannabis consumption occurred. This, however, is a new concept and is yet to be seen as legitimate.

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The fact is, alcohol and cannabis just do not react the same with the human body, which means testing for THC the same way may never be as effective as the powers that be want it to be. “We’re applying the alcohol rules to a substance that doesn’t play by them,” Nick Morrow, a retired Los Angeles Sheriff’s Department narcotics investigator told CNN. While it is normal to want to test people the same for marijuana as you do alcohol, especially when on the road, it really is two different breeds, which is why this $1.4 million dollar investment might seem like a lot of money to come up with a breathalyzer, but really it is a drop in the bucket — and a long shot at that.

Another aspect that separates cannabis from alcohol is the fact that it affects people differently. That is to say, if you give someone several shots, their motor functions are all but certain to change. Cannabis has different effects on people, and sometimes affects the same person differently depending on a variety of factors. This means the standard field sobriety tests used to help determine drunk driving do not hold the same weight when it comes to cannabis. “You could absolutely have people under the influence of marijuana who had poor physical coordination,” Colorado attorney Chris Halsor told Discover Magazine in regards to cannabis sobriety tests. “And you could also have people who were completely baked out of their minds and could ace them.”

Another variable at play is the theory that blood and saliva may not be accurate tools to measure marijuana intoxication levels in general. A 2021 study from The University of Sydney suggests that blood and saliva are not reliable ways to test for marijuana impairment. According to a recent study by the University of Sydney, blood and oral fluid THC concentrations are relatively poor or inconsistent indicators of cannabis-induced impairment. If more studies come out to suggest the same, then even the most accurate THC breathalyzer may still not be an accurate tool for deciding whether or not a person is under the influence.

If the University of Sydney study is any indication, testing for marijuana intoxication is likely to be a long and difficult journey to prove definitive. Still, this newest study and its fresh approach at multiple measurements is a unique look at how cannabis intoxication might present itself on a person’s breath.

Even with elaborate and accurate equipment, there are likely to be many legal battles fought over how legitimate the equipment is. This, combined with no Federal guidelines to guide states, there may even be wildly different laws and testing methods based on which state you are driving in — so buckle up, this may be a bumpy ride.