Although some states are legalizing weed, driving under the influence of marijuana is still illegal in all 50 states.
The problem, however, is that it is more difficult for police to test drivers for cannabis during a DUI stop than for alcohol.
“The science is very murky on what good indicators are for impairment by marijuana because someone could just smell like it or have consumed it a few hours ago and it’s difficult to say if they’re impaired or not,” Sarah Schielke, a Colorado defense attorney who specializes in DUI
marijuana cases, told the International Business Times.
Urgent: Should Marijuana Be Legalized in All States?
Still, as marijuana becomes more of a norm for Americans in states where the drug has been legalized, police employ several methods to test drivers and prevent stoned driving. Below are five strategies police use to stop stoned drivers:
1. Marijuana Field Sobriety Tests
Much like with alcohol DUI stops, police are likely to conduct field sobriety tests. For suspected marijuana cases, the most common tests are the horizontal gaze nystagmus test, the walk and turn test, and the one leg stand. Although field sobriety tests are highly effective in testing for alcohol use, they are much less effective in testing for marijuana use. Regardless, if pulled over for a marijuana DUI, police are likely to conduct sobriety tests before anything else.
2. Blood and Urine Tests
In some states, such as California, drivers are required to take blood or urine drug tests if police have probable cause to suspect a person was driving under the influence of marijuana. However, blood and urine tests only show whether THC, a principle component of cannabis, has been in a person’s system in the preceding few hours, not whether the person was high while driving,
according to DUI Ease.
3. Saliva Swab Tests at Checkpoints
The Los Angeles Police Department (LAPD) has set up sobriety checkpoints where they use a swab test to determine if drivers have alcohol or marijuana in their systems. LAPD had cited increasing marijuana use as their reason for setting up the checkpoints, but many Americans think the checkpoints are an invasion of their privacy.
4. Breathalyzer
Although there is currently no effective breath test for marijuana, police and researchers are working to create one. Police hope that an effective breath test would be able to determine whether an individual was under the influence while driving, unlike other sample tests that only reveal whether someone has had marijuana in their system prior. However, Schielke admits that “the only way we’re going to get there is with more science.”
Urgent: Should All Police Officers Have to Wear Body Cameras?
5. Education
Colorado police and State Patrol are backing the Colorado Department of Transportation’s $1 million bilingual television ad campaign that aims to prevent stoned driving. The ads feature people forgetting to do everyday things like grilling without propane and playing basketball without a hoop. Avon police chief Bob Ticer admits that “enforcement is very important when it comes to impaired driving, but education is equally important,"
The Denver Post reported.
© 2026 Newsmax. All rights reserved.