{"id":286633,"date":"2019-09-23T11:28:12","date_gmt":"2019-09-23T16:28:12","guid":{"rendered":"https:\/\/content.findlaw-admin.com\/ability-law\/dui\/arrests\/a-marijuana-breathalyzer-is-here-but-skepticism-remains-high.html"},"modified":"2026-04-06T11:02:57","modified_gmt":"2026-04-06T16:02:57","slug":"a-marijuana-breathalyzer-is-here-but-skepticism-remains-high","status":"publish","type":"page","link":"https:\/\/www.findlaw.com\/dui\/arrests\/a-marijuana-breathalyzer-is-here-but-skepticism-remains-high.html","title":{"rendered":"Are There Roadside Cannabis Tests for DUI?"},"content":{"rendered":"\n
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Are There Roadside Cannabis Tests for DUI?<\/h1>\n\n
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\n By Susan Buckner, J.D.<\/a> | Legally reviewed by Laura Temme, Esq.<\/a>\n | Last updated\n
\n \n <\/i>\n Legally Reviewed\n <\/summary>\n\n
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This article has been written and reviewed for legal accuracy, clarity, and style by FindLaw\u2019s team of legal writers and attorneys<\/a> and in accordance with our editorial standards<\/a>.<\/em><\/p>\n\n <\/div>\n <\/details>\n\n

\n \n <\/i>\n Fact-Checked\n <\/summary>\n\n
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The last updated date refers to the last time this article was reviewed by FindLaw or one of our contributing authors<\/a>. We make every effort to keep our articles updated. For information regarding a specific legal issue affecting you, please contact an attorney in your area<\/a>.<\/em><\/p>\n\n <\/div>\n <\/details>\n<\/section>\n\n\n

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Roadside cannabis tests exist, but they are limited and often less reliable than alcohol testing methods. Drug tests don\u2019t accurately measure impairment<\/span> levels like breathalyzers<\/span> do for alcohol. These tests can only detect the presence of THC<\/span> in a person’s system, not whether someone is currently impaired while driving. Most states base DUI charges on impairment<\/span>.<\/p>\n\n <\/div>\n\n\n\n

While marijuana is illegal under federal law, the state level may allow legal marijuana. As of 2026, 24 states have legalized recreational marijuana use<\/span>, and 38 allow at least some form of medical marijuana<\/span>, cannabis, or THC<\/span> (tetrahydrocannabinol<\/span>) use.<\/p>\n

Yet, marijuana use<\/span> presents a problem to traffic safety laws. Just as alcohol is legal but drinking and driving is not, driving while high is also illegal. Even if marijuana is legal in your state, it\u2019s important to understand the current status of cannabis testing before you hit the road.<\/p>\n

A drug DUI<\/span> charge<\/span><\/a> comes with the same severe consequences as impaired driving<\/span> due to alcohol. In this article, learn how states measure impairment<\/span> based on cannabis use \u2014 and the reliability of those tests.<\/p>\n

But these laws vary significantly among states, and they change frequently. If you\u2019re facing a drug DUI<\/span> charge<\/span> or another impaired driving<\/span> charge, consult with a local DUI<\/span> attorney<\/a> as soon as possible. They can help you build a defense based on your state\u2019s DUI<\/span> and marijuana laws. A lawyer can protect your rights.<\/p>\n

Driving Under the <\/span>Influence<\/span> of Marijuana<\/span><\/h2>\n

Most state laws consider<\/a> \u201cdriving under the influence\u201d to mean the influence of drugs<\/span> as well as alcohol. Even prescription medications<\/span> can result in DUI charges<\/a> if they cause impairment<\/span>. Any substances that cause drowsiness, dizziness, blurred vision, or slowed reaction time can impair your ability to drive.<\/p>\n

But standard field sobriety tests<\/span><\/a> were designed for alcohol impairment<\/span> and may not be as reliable for detecting drug impairment<\/span>.<\/p>\n

Testing Alcohol Intoxication vs. Marijuana <\/span>Impairment<\/span><\/h3>\n

When it comes to alcohol, state laws agree that if the average person reaches a blood alcohol concentration (BAC) of 0.08%, they are impaired and shouldn\u2019t be driving.<\/p>\n

However, unlike alcohol, there is no blood level of <\/span>THC<\/span><\/a> at which an average person becomes impaired. In a majority of states, there is no \u201cacceptable\u201d THC<\/span> or blood-cannabinoid<\/span> level for driving. Instead, some state legislators have turned to zero-tolerance or “per se” laws<\/a>.<\/p>\n

Zero-Tolerance Laws for Drugged Driving<\/span><\/h3>\n

Under a zero-tolerance law, any amount of drugs in a person’s system creates a presumption of impairment<\/span>. Meanwhile, a per se law sets a threshold for presumed impairment<\/span>, similar to the 0.08% BAC for alcohol.<\/p>\n

Here\u2019s a breakdown of states\u2019 zero-tolerance and per se<\/span> laws:<\/p>\n