Imagine being charged with a DUI marijuana even though you haven't ingested any cannabis for a full month. That could actually happen. Pictured: Trooper Gordon McCaslin uses a pupilometer while conducting a twelve-step DRE (Drug Recognition Expert) test on DEC (Drug Evaluation and Classification) coordinator Robin Rocke of the Colorado Department of Transportation on March 6, 2014. (Craig F. Walker, The Denver Post)

Why this pressing issue should be among cannabis consumers’ most urgent concerns

While marijuana consumers and enthusiasts might be rejoicing over the recent string of electoral victories for cannabis legalization, they also still face some new and quite sobering realities.

Every state has DUI laws to deal with people driving under the influence of alcohol. “But unlike the laws for alcohol-impaired driving,” notes the Governors Highway Safety Association, “those that address drug-impaired driving are nuanced, difficult to enforce and prosecute and vary substantially by state.”

Combine this patchwork of laws with sobriety-testing methodologies that aren’t rooted in science (more on that soon) and the issue of testing for cannabis intoxication should already be concerning to anyone who ingests marijuana in any form and in any state and for any reason. When you factor in THC’s fat-soluble composition — meaning that it can be detected in the bloodstream weeks if not months after a heavy user’s last toke — and the seriousness of the issue is escalated even further.

Imagine being charged with a DUI for marijuana even though you haven’t ingested any cannabis for a full month. That could actually happen.

As Associated Press transportation reporter Joan Lowy recently wrote, “Determining whether someone is impaired by marijuana, as opposed to having merely used the drug at some time, is far more complex than the simple and reliable tests that have been developed for alcohol impairment.”

What the laws say

According to the Governors Highway Safety Association, there are two basic sets of laws that states use when dealing with drugged driving. Zero tolerance, as the name implies, means it’s illegal to drive after cannabis has been “possessed and used.” Then there are Per Se laws, which make it illegal to drive “with amounts of specified drugs in the body that exceed set limits.”

And those marijuana-specific impaired driving laws vary widely, especially in these early days of legalization.

Arizona, for example, has legalized medical cannabis. But last year Arizona’s Supreme Court ruled that medical marijuana cardholders are not immune from the state’s zero tolerance DUI marijuana law, which “prohibits drivers from having in their bodies any amount of marijuana or its chemical compound that causes impairment,” according to the Associated Press.

The controversy with these DUI marijuana laws focuses on detection of THC, the aforementioned chemical compound in cannabis that makes you high, in a person’s system.

Those stopped and tested by law enforcement in a zero tolerance state — even if it’s been days since you imbibed and you’re in no way intoxicated during your encounter with the law — could still face some very serious penalties.

Colorado on the other hand, uses Per Se limits of five nanograms of THC per milliliter of blood to determine if a driver can be prosecuted for DUI marijuana. But the state’s Department of Transportation acknowledges that “no matter the level of THC, law enforcement officers base arrests on observed impairment.”

And that risk of being prosecuted for DUI marijuana — whether you’re high or not — is growing, as some lawmakers, law enforcement organizations and drivers’ groups fear that the spreading cannabis legalization movement means more stoned drivers on America’s roads.

“If you’ve had marijuana whether it’s medicinal or otherwise, don’t drive,” Beth Mosher, spokeswoman for the Chicago branch of motorist group AAA told WGN-TV in May. “It’s really that simple.”

What science says about reliable testing

But AAA is also finding fault with current attempts to develop a cannabis sobriety test that’s equal to those used by police to detect drunk drivers.

“There is understandably a strong desire by both lawmakers and the public to create legal limits for marijuana impairment in the same manner we do alcohol,” AAA president and CEO Marshall Doney said earlier this year. “In the case of marijuana, this approach is flawed and not supported by scientific research.”

Indeed, despite claims by companies saying they may soon have a marijuana breathalyzer product ready for law enforcement, an article in the November issue of Scientific American notes those breathalyzer-type devices for measuring cannabis impairment are nowhere near as accurate as those detecting a driver’s blood alcohol level.

The article quotes Nick Morrow, a retired Los Angeles County Sheriff deputy and court-qualified expert in the study of drug symptoms who says there’s a rush of companies wanting to release the first widely available cannabis field sobriety test on the market.

“Breath, oral, fluid, saliva — all of them are competing to come out with the easiest, greatest devices,” Morrow said. “Maybe those devices aren’t ready for prime time yet, but everybody wants to get the patents. As far as having something that really works, defense and prosecutors can agree — the science is not there yet.”

Lawmakers and police want a solution now

The political pressure for the development and use of a test comparable to an alcohol breathalyzer, however, remains great.

In California, which just voted to legalize recreational cannabis, a Republican state assemblyman has introduced a measure that would allow law enforcement to collect “spit swabs” from motorists they suspect are driving under the influence of marijuana. But critics of the bill note that saliva testing is still in its experimental stages and they question the test’s reliability.

Alex Kreit, an associate professor at the Thomas Jefferson School of Law in San Diego, believes that until science catches up with the law, legislatures and law enforcement shouldn’t be jumping the gun and setting up uncertain THC level metrics — just to show they’re doing something when it comes to the issue of DUI marijuana cases.

Instead, he suggests a two-tiered approach to the issue.

“One, to invest the money into trying to do real scientific research on getting a numerical/biological standard — to say we can do a saliva test or blood test or whatever the test might be,” he told The Cannabist in a phone interview. “Based on that test we can have a reliable determination of whether somebody’s intoxicated.

“And then, number two, while we’re investing in trying to get that standard, taking time to invest resources (towards) training officers to do roadside impairment tests that are not based on blood tests. Those tests are going to be able to help find people who are genuinely imposing a risk, regardless of what substance they’re on, whether it’s marijuana or prescription drugs.”

But many police departments aren’t waiting around for scientists to build a better cannabis mousetrap, or to develop more definitive roadside marijuana sobriety tests.

“Faced with the prospect of marijuana being as legal as alcohol, law enforcement officials in some states have claimed they need a non-zero numerical threshold, like .08 percent (the blood alcohol level that makes you legally drunk), to successfully combat DUI marijuana,” Andrea Roth, an expert on marijuana DUI issues and a professor of law at University of California, Berkeley, wrote last year in the California Law Review.

The general public, she says, seems to understand that “something is amiss” when it comes to these seemingly arbitrary standards. But she notes that many marijuana advocates appear willing to trade off sometimes-harsh measures in the hopes that these limits “will eventually be changed to something more rational.”

How this looks in real life

If such cases ever get to a jury trial, law enforcement officials say the chance of a marijuana impairment conviction is never certain.

“The problem we have in prosecuting cases now is that without a set THC limit, you are really rolling the dice with the juries,” Newark, Calif., police chief James Leal told the Los Angeles Times in October. “You are finding district attorneys are having a hard time prosecuting cases or they are declining to prosecute because they are having a harder time winning.”

One recent example is the case of Colorado resident Abby McLean, who was stopped at a DUI checkpoint two years ago and told by local police she smelled of marijuana. A blood test showed that McLean, who acknowledged being a heavy cannabis user, had high levels of THC in her system. But her attorney, Nadav Aschner, argued in court that frequent marijuana users can have high THC levels for hours after imbibing.

“Even the state’s experts will say that number alone is something, but generally not enough and we really hammered that home,” Aschner told Colorado Public Radio.

McLean’s trial ended in a hung jury, and she pled to a lesser charge.

The Thomas Jefferson School of Law’s Kreit said there have been challenges to the constitutionality of “zero-tolerance” marijuana DUI laws, but that most of those challenges have been defeated by what’s called a “rational basis” standard. According to that test, as defined by the Cornell Law School’s Legal Information Institute, “the courts will uphold a law if it is rationally related to a legitimate government purpose,” which in the case of marijuana DUI is public safety.

At the same time, drivers fearing DUI marijuana prosecution are at least partially covered by the Fourth Amendment, which protects an individual against unreasonable government searches and seizures. Such a Fourth Amendment case was litigated several years ago by the U.S. Supreme Court — which at the time ruled that a Missouri man suspected of drunk driving could not have his blood drawn and tested without a warrant, his consent or pressing legal circumstances.

But refusing a DUI screening often has its own consequences. In Colorado, a driver who refuses such a test can end up with their license revoked for one year.

In her California Law Review article, Roth concluded that if cannabis sobriety tests remain uncertain for the foreseeable future, “then the answer should not be to settle for incoherency in our criminal law in the name of securing more convictions.”

Instead, she added, “we should be guided by science in tackling the issue of drugged driving, whether our goal is to achieve justice, to promote public safety, or to have the audacity to try to do both.”