Military and Police

Police and Cannabis Breathalyzers – Not Your Average DUI Anymore

“There is evidence supporting continued psychomotor impairment after three weeks of abstinence in chronic frequent smokers.”

Whether Attorney General Jeff Sessions remains a member of the White House Cabinet is tentative at the moment. It could go either way, although I believe his political post is secure as is. Mr. Sessions remains a stalwart oppositionist in the ongoing debate surrounding the decriminalization of cannabis as well as present hiccups in medical marijuana legislation across the country.

Despite the seeming impasses and obstructionist perspectives, a majority of proponents are speaking out. Regardless of what evolves between weed wackers and cannabis consumers — and any laws for or against marijuana use — it is nonetheless illegal to drive impaired, even with medical marijuana cards in pockets.

That last factor segues to law enforcement’s role in verifying driver impairment stemming from cannabis use. Police still lack any quantifiable scientific instrumentation to validly field-test motorists stopped and suspected of DUI of the leafy substance.

I recently reviewed material whereby San Diego police claimed they have breathalyzers in their arsenal and that, allegedly, local courts have given the thumbs-up to law enforcers to use the results from these in arrests and present them as admissible findings in DUI cases.

San Diego Police Officer Mark McCullough stated that the marijuana breathalyzers his department utilize detect the “THC [tetrahydrocannabidol] that is in the marijuana that you can get by smoking or using an edible or using an oil.” In addition to cannabis, the San Diego PD breathalyzer reportedly also tests for the presence of “psychoactive components” found in prescription drugs, methamphetamine, methadone and cocaine.

After hearing this, I looked up the particular breathalyzer the San Diego police use. The manufacturer of the breathalyzer instrumentation claims that “The Dräger DrugTest 5000 is an easy to use mobile drug screening system that uses oral fluid to test for seven types of the most commonly abused drugs. This quick drug test provides a non-invasive alternative to the hassle of collecting urine or blood samples. FOR LAW ENFORCEMENT USE ONLY.”

Not so fast, says California-based criminal defense attorney Cole Casey. “That’s utter nonsense. There’s no science to back this up whatsoever,” said Casey. It is Casey’s contention that only a blood test — not a breath test — can scientifically and legally distinguish if someone is too weed-wacked to operate a motor vehicle. But if the instruments San Diego cops use work by way of saliva samples, that implies DNA strands determine the presence of psychoactive components in saliva.

Mr. Casey argues, “The biggest problem you’re going to have in court is that there is no legal limit for marijuana. So, the Dräger 5000 comes out and says here is how much cannabis is in their system. What do you do with that information?” Mr. Casey spoke those words in June 2017. However, some case precedent was already set earlier in a California courtroom.

In a February 2016 press release published by the breathalyzer manufacturer, it cited that a California judiciary found their instrument met conclusive results via a bona-fide scientific basis, thus accepting the impairment results collected by police which led to a manslaughter conviction, a three-year state prison sentence and fines. That particular case is “The People of the State of California v. Junior Salas,” coined as a “landmark case” in which oral swab technology was used by police after Salas’s vehicle struck another motorist whose passenger was killed in the crash.

According to a article, “A breathalyzer test and a blood test administered about three hours after the accident showed Salas had a blood-alcohol concentration [BAC] of 0.03 percent” and that the “blood test also showed Salas had 100 nanograms per milliliter of methamphetamine, and a 1.1 nanograms per milliliter concentration of marijuana [emphasis added].” If I comprehend that correctly, it seems the BAC, not necessarily the breathalyzer, was the catalyst supplying evidentiary value leading to a conviction.

San Diego police claim they also administer a blood test in tandem with the marijuana breathalyzer.

The breathalyzer maker’s company president, Michael Willis, said of his product:

“Dräger understands that DT5000 results need support from policymakers and throughout the criminal justice system, including law enforcement, prosecutors and judges. Due to its broad reach, the DT5000 screening system has undergone extensive, independent, scientific validation and been utilized in approximately one million tests worldwide. This first Kelly-Frye hearing, as well as the push by the Kern County District Attorney’s Office for oral fluid result admissibility in the case, is confirmation that the DT5000 is on its way to becoming a standard screening method for DUID investigations and prosecutions.”

Kelly-Frye hearings stem from a “California statute that requires … a hearing at which both the defense and prosecution are allowed to present expert testimony as to the reliability of new scientific methods of obtaining evidence.”

Although this is not about alcohol consumption, a few hiccups present from a differing perspective, including an argument contending Mr. Casey’s stipulation regarding blood test results.

An article in more than suggests there is no current scientifically validated breathalyzer yet available and that, even if there were, the dynamics of cannabis and how it registers in humans varies so widely that to arrive at conclusive figures seems improbable, at least at this point.

In her piece covering the level of cannabis impairment and how authorities can legally discern how much is concentrated in a driver, NPR’s Rae Bichell said “Though a blood test exists that can detect some of marijuana’s components, there is no widely accepted, standardized amount in the breath or blood that gives police or courts or anyone else a good sense of who is impaired.”

What she is referring to is the seemingly elusive determinants pertaining to conclusive figures regarding cannabis chemicals in the human body. Unlike alcohol’s traces of ethanol which courses through the human body’s water content (a lot, so it is dispersed/diluted) and reduces rapidly, THC is different in that it is absorbed by fat cells and thus metabolizes in the body to varying intervals based on a person’s size, gender, and the frequency/method/type of marijuana use. In essence, people who engage in marijuana use bodily-breakdown the THC differently. That may bode well for some drivers and not for others.

Some studies gave insights while also making it more perplexing, especially in terms of enforcement leading to adjudication. The National Institute of Health (NIH) stipulates, “In chronic cannabis users, it is particularly difficult to determine whether a positive result for cannabis represents a new episode of drug use or continued excretion of residual drug.”

Regardless, that plays no particular role in how police can legitimately calculate a driver’s sobriety but it does imply elevated impairment potential. Fresh tokes caked atop residual trace elements harbored in the human body increases purported dangers of operating a car while high on weed.

A study published in Clinical Chemistry indicated that “cannabinoid blood and plasma concentrations were significantly higher in frequent smokers compared with occasional smokers.” Not much of an earth-shattering surprise there. The study went on to say “cannabis smoking history plays a major role in cannabinoid detection. These differences may impact clinical and impaired driving drug detection.”


Regardless of what science may invent to gauge cannabis level in motorists, another dilemma exists. A study was conducted at an inhabitable research facility where test subjects were restricted from marijuana use of any kind for 30 days. Upon conclusion of the study, the subjects were tested to see the physiological breakdown of THC in the human system. Astonishingly, although there was no pot smoking for one full month, the results indicated each subject had traces of cannabis in their bodies and in varying degrees.

The study published in Clinical Chemistry corroborated this, saying, “Because of their high lipophilicity, which results in extensive storage and prolonged release from adipose tissue, as well as enterohepatic recirculation, cannabinoids remain in plasma for extended periods of abstinence in chronic daily smokers.”

In short, the human body is more of a storing house than it is a clearing house when it comes to THC use and buildup. Biochemically, our complex human design may not serve us well in terms of legal implications, despite flaws or advancements in breathalyzer technology, inflating the legal pickle drivers may find themselves in down the road.

Thus, as it relates to levels of cannabis use and what any potential instrumentation may register, the results may never be consistent and substantive enough to legally charge someone. In other words, it is not so much an argument over the methodology as it is physiological variations which are not universal — one’s metabolic breakdown either hinders or hastens the THC trace elements in the human body. “Extensive liver metabolism probably reduces the oral bioavailability of THC by 4-12%,” indicates a NIH study.

If measures vary widely, according to scientists, suspected impaired drivers cannot be placed in the same conclusive basket. To cops working the DUI scene, that poses a rather chronic head scratcher. To would-be violators, it may or may not be your lucky day.

Back to square-one … perhaps leading to a fusion of technology/legality to form the definitive basis for cops to weed-out vagaries, make DUI arrests, and successfully cinch impaired drivers. Like whack-a-mole, cops can aim and hit it square on the head or guess where the critter will pop-up only to be wrong. In recent years, science has been instrumental in distinguishing cold-case-breaking details with alcohol impairment with the specificity to make a chess savant salivate. Will we get there in terms of cannabis sobriety testing equipment?

Per the NIH and testing for cannabinoids,

“Urine is the preferred sample because of higher concentration and longer detection time of metabolites in it. Moreover, urine can easily be sampled. Apart from cut off concentration, sensitivity and specificity of assay other factors like route of administration, amount of cannabinoids absorbed, body fat contents rate of metabolism and excretion, degree of dilution and time of specimen collection also influence detectability of ▵9_THC and its metabolites.”

Yet, when considering real-time results at the scene of a DUI stop, urinalysis is prohibitive. Police have to endure the process of health professionals collecting samples at recognized facilities — not roadside. And that puts us back in the realm of breathalyzer technology.

According to the National Institutes of Health (NIH), “Cannabinoids exert various physiological effects by interacting with specific cannabinoid receptors (CB receptors) present in the brain and periphery. CB1 receptors in the brain are particularly concentrated in anatomical regions associated with cognition, memory, reward, anxiety, pain sensory perception, motor co-ordination and endocrine function.”

As well, NIH informs us, “Cannabis is known to have behavioral and physiological effects. Behavioral effects include feeling of euphoria, relaxation, altered time perception, lack of concentration and impaired learning” [emphasis added]. Since driving is a task requiring ultra-concentration and practically demands a continuum of learning — as we drive, things are changing all around with rapidity, and real-time adaptations are requisite — there is no argument against DUI enforcement … only how we arrive at the most definitive course of policing buzzed operators and practicable devices to reinforce reasonable suspicions.

Not only are we still studying and learning about the effects of cannabis and various THC strains but we may also be getting closer to engineering instruments to equip our law enforcement officers with field-sobriety tools to constitutionally enforce impaired driving.

As Clinical Chemistry stipulated: “There is evidence supporting continued psychomotor impairment after three weeks of abstinence in chronic frequent smokers, suggesting that driving ability is impaired at the time of these low blood THC concentrations.” We are definitely on the right road … with some miles to go.

As Franklin D. Roosevelt once said: “It is common sense to take a method and try it. If it fails, admit it frankly and try another. But above all, try something.”

Stephen Owsinski

Stephen Owsinski is a Senior OpsLens Contributor and retired law enforcement officer whose career included assignments in the Uniformed Patrol Division and Field Training Officer (FTO) unit. He is currently a researcher and writer. Follow Stephen on Twitter @uniformblue.

Join the conversation!

We have no tolerance for comments containing violence, racism, vulgarity, profanity, all caps, or discourteous behavior. Thank you for partnering with us to maintain a courteous and useful public environment where we can engage in reasonable discourse.