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Breathalyzers for Marijuana Use: Are They Reliable?

Posted by Taryn Gunn | Jun 14, 2023 | 0 Comments

When it comes to cannabis, the legal landscape has transformed dramatically over the years. Today, most U.S. states have relaxed their laws, allowing marijuana use for either medicinal or recreational purposes. However, all states share the common goal of maintaining safe roadways. This prompts the need for a reliable method to identify recent cannabis use, particularly for motorists. But just how reliable are breath tests for this purpose? Dan Kingston on explores this issue in his recent article, "Breath Testing for Marijuana Is Unreliable Indicator of Recent Use."


The idea of a breathalyzer for marijuana is far more challenging than its alcohol counterpart. When consuming alcohol, people exhale it in large quantities, making it easier to measure. However, the intoxicating component of cannabis, known as THC, is believed to be conveyed inside tiny aerosol particles that people exhale. This makes it exceptionally difficult to accurately measure their THC content.

In a recent study conducted by researchers from the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder, breath samples were collected from individuals before and after they smoked high-THC cannabis. The samples were then analyzed using laboratory instruments, not a handheld device, to determine the THC levels. The goal of this research was to establish a protocol that yields reproducible results, a significant step towards a reliable, field-based method for detecting recent marijuana use.


According to NIST supervisory chemical engineer and study author Tara Lovestead, "One key question that we cannot yet answer is whether breath measurements can be used to distinguish between a person who uses cannabis regularly but hasn't done so lately, and someone who consumed an hour ago."

The study faced some hurdles, the major one being the variability in THC levels in the breath samples collected both before and after marijuana use. This inconsistency made it hard to determine if the participants had used cannabis recently based on the THC concentration in their breath.

Despite these initial challenges, the research is ongoing. The Department of Justice's National Institute of Justice has awarded the research team an additional $1.5 million grant to continue the study, which will involve a larger number of participants and thus hold more statistical weight.

"A lot more research is needed to show that a cannabis breathalyzer can produce useful results," commented NIST materials research engineer and co-author Kavita Jeerage. She emphasized that the results of a breathalyzer test can greatly impact a person's life, hence the need for accuracy and confidence in the results.


While breath tests for marijuana might not currently provide a clear-cut indication of recent use, research is underway to improve their reliability. Until then, those facing charges related to marijuana DUIs are advised to seek competent legal counsel.

If you or a loved one has been charged with a marijuana DUI, it's crucial to remember that you have rights. We at our firm are experienced in defending such cases and can provide the legal guidance you need. We will analyze the specifics of your situation and advocate for your best possible outcome. Contact the Hamp Law Offices today for a consultation, and let us assist you in navigating the legal complexities surrounding marijuana DUI cases.

Note: This blog post is based on information provided in the article "Breath Testing for Marijuana Is Unreliable Indicator of Recent Use" by Dan Kingston on

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