Alcohol breathalyzers have been around for decades, but testing drivers for cannabis impairment is much more complicated. Researchers have spent years working on devices that could potentially detect THC in a person's breath, including research that once made headlines here in Washington.
So, did the cannabis breathalyzer ever become a normal part of traffic stops?
Not exactly.
While technology for detecting recent cannabis use continues to be researched, Washington's current DUI laws still rely on blood testing rather than a roadside THC breathalyzer to determine a driver's THC concentration.
Why Is Cannabis Harder to Test Than Alcohol?
Alcohol and cannabis behave very differently in the body.
With alcohol, breath alcohol concentration can be measured using established breath-testing technology. Cannabis presents a different challenge because THC does not have the same straightforward relationship between the amount detected in someone's body and how impaired that person may be at that exact moment.
THC levels can also vary significantly depending on factors such as:
- How recently cannabis was consumed
- How much was consumed
- The type of cannabis product
- A person's metabolism
- How frequently that person uses cannabis
That makes creating a simple "THC breathalyzer" much more complicated than adapting the technology already used for alcohol.
Washington Researchers Have Studied THC Breath Testing
Washington State University researchers were working on cannabis breath-testing technology more than a decade ago. The goal was to develop a portable device that could help identify recent cannabis exposure using a breath sample.
At the time, the idea received a lot of attention because Washington had recently legalized recreational cannabis and there was significant interest in finding a roadside test comparable to an alcohol breathalyzer.
Research into cannabis breath testing has continued in different forms since then, but THC breathalyzers have not replaced the methods currently used to investigate cannabis-impaired driving in Washington.
How Does Washington Test for Cannabis DUI Today?
Washington law treats driving under the influence of cannabis seriously.
For drivers age 21 and older, Washington law establishes a THC concentration of 5.00 nanograms or more per milliliter of whole blood within two hours of driving as one way a person can meet the state's DUI standard.
But that number isn't the only thing that matters.
A person can still be arrested and prosecuted for DUI based on evidence that they were impaired or affected by cannabis, even when a blood test does not show a THC concentration of 5.00 nanograms or higher.
Law enforcement may consider things such as:
- Driving behavior
- The driver's behavior and physical condition
- Roadside sobriety testing
- Statements or other observations
- Blood test results
Unlike alcohol testing, Washington's THC concentration is determined through blood analysis, not a standard roadside breathalyzer.
Does 5 Nanograms Mean Everyone Is Impaired at the Same Level?
No. Cannabis doesn't affect every person in exactly the same way.
Tolerance, frequency of use, dose, product type and individual metabolism can all affect how someone experiences THC. A blood THC number also doesn't function exactly like blood alcohol concentration.
That's one reason cannabis impairment continues to be a difficult area for researchers, lawmakers and law enforcement.
The important thing for drivers is much simpler: if cannabis is affecting you, don't drive.
What About Edibles?
Edibles make timing especially important.
Inhaled cannabis generally produces noticeable effects relatively quickly. Edibles can take much longer to kick in, and their effects can also last significantly longer.
That means someone shouldn't assume they're safe to drive simply because they consumed cannabis several hours earlier.
If you're still feeling the effects, you're not ready to drive.
Will We Eventually Have a Cannabis Breathalyzer?
Possibly.
Researchers continue studying ways to identify recent cannabis consumption and better measure impairment. A reliable roadside cannabis test could potentially give law enforcement another tool, but detecting THC and determining actual impairment are not necessarily the same thing.
That's the challenge researchers have been trying to solve for years.
For now, there isn't a cannabis equivalent of the familiar alcohol breathalyzer being routinely used to establish a driver's THC concentration under Washington's DUI law.
Cannabis Is Legal. Driving Impaired Isn't.
Washington legalized recreational cannabis for adults 21 and older, but legalization never made it legal to drive while impaired.
Plan your ride before consuming cannabis. Use a designated driver, rideshare, taxi or public transportation, or simply stay where you are until you're confident you're no longer feeling the effects.
Cannabis may be legal in Washington, but getting behind the wheel while impaired isn't worth the risk.
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