A Gray Area

Measuring cannabis impairment of drivers remains an elusive target for New Mexico and nationally

March 30, 2022

7:06 AM

SFR FILE Photo

Carefully tended roadside crosses mark the locations of deadly automobile crashes—and stand as reminders of the persistent reality that New Mexico still grapples with the costs of drunken driving.

In 2018, there were 113 alcohol-related fatalities in the state. The next year, 129 people died in crashes involving drinking and driving—a 14% increase. Such statistics have haunted New Mexico for decades.

Less clear is how the beginning of recreational cannabis sales will impact the number of impaired drivers on the road.

While smoking weed has been legal for almost a year, the kickoff of adult-use sales invites a wider range of the population to partake, which suggests the possibility of more high drivers. And just like other states that legalized recreational weed some time ago, New Mexico faces challenges associated with determining the level of impairment of drivers with cannabis in their systems.

Unlike alcohol, which most people metabolize similarly, the complexities of how different bodies process and store THC, the psychoactive component of cannabis that can impair drivers, are messy.

Brian Vicente, a founding partner of Vicente Sederberg LLP, a Colorado-based cannabis law firm, explains the first state to legalize the drug for recreational use, alongside Washington, took its time to find firm ground on which to regulate driving while high. New Mexico’s northern neighbor legalized recreational sales eight years ago.

Colorado passed a law that established a legal limit, which Vicente equates to the cap on blood alcohol concentration drivers know. The threshold in Colorado is 5 nanograms per milliliter of THC, measured through a blood test.

A number of other states have adopted similar threshold laws, but the science behind the legal limit is hazy. A 2019 report from Michigan’s Impaired Driving Safety Commission found that blood concentration of THC in an individual is “indicative of exposure, but…not a reliable indicator of whether an individual is impaired.”

“The numbers are going to be different for everybody,” Douglas Hiatt, a criminal defense attorney in Seattle, tells SFR, referring to the blood concentration of THC for different people. “You can’t have a generalized test of impairment that’s going to be valid, and that’s really what the problem is.”

Hiatt explains this system creates a constitutional minefield around equal protection, given that THC is stored for longer periods of time in the bodies of those with more fat, and generally those who ingest cannabis more frequently. Alternatively, alcohol, which is soluble in water, is cycled through most bodies at a relatively consistent and quick rate.

His home state of Washington, like Colorado, also relies on a threshold limit for THC, but Washington’s law doesn’t include an iron-clad clause that means, if a driver is above that limit, they’re guilty even without solid evidence that they were impaired.

Unlike Washington and Colorado, New Mexico doesn’t have a blood limit for THC. Rather, the state relies on a blanket approach to all drugged driving: “It is unlawful for a person who is under the influence of any drug to a degree that renders the person incapable of safely driving a vehicle to drive a vehicle within this state,” reads the relevant statute.

That level of impairment is left up to the discretion of police officers known as Drug Recognition Experts, who are trained to identify individuals under the influence of drugs and whether someone is too high to be driving legally.

DWI Unit Sgt. Heinz De Luca with Santa Fe Police Department explains that DRE officers conduct an investigation when a driver is suspected of being under the influence of drugs and “based on that entire picture, then the officer could arrive at the conclusion that…this person is impaired and not able to drive safely.”

On the issue of probable cause, De Luca explains, since cannabis was legalized, unsmoked pot can’t be used as an indicator that a person is impaired, similar to unopened containers of alcohol.

“Just because a person has a can of beer in the vehicle doesn’t mean that I’m going to search the car,” he tells SFR. A DRE or officer with Advanced Roadside Impaired Driving Enforcement (ARIDE) training, a similar but less extensive program to DRE, would look for other signs such as bloodshot eyes or slurred speech, De Luca adds.

Last April SFPD had two DREs on the force—almost one year later that’s still the case, though De Luca says another officer will complete the training by early May. He says six DREs would be necessary to cover all seven days of the week.

Larissa Breen, an attorney with Santa Fe’s Dan Cron Law Firm PC, says New Mexico’s method of assessing impaired drivers isn’t perfect given the limitation of cannabis.

“It’s really hard to come up with some kind of bright-line standards that we can give to officers or judges or attorneys and say…'This will always be an indication of inappropriate use,’ and you just really can’t do that with weed,” she tells SFR.

Additionally, Breen says, more details need to be “hashed out” to determine “what irresponsible use actually looks like, who the real offenders are.” The risk being, Breen explains, that with “the net being cast so broadly, to catch anybody who seems like they might be using inappropriately, they kind of get swept up” in the justice system, which has historically resulted in over-policing of low-income communities and people of color.

Vicente, the Colorado attorney, explains his state found success in robust education campaigns to inform the public about safe use of cannabis.

“There’s a degree of public education that I think would be smart to engage in New Mexico so people can understand when they’re impaired or not, and if they’re breaking the law,” he says.

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