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The Latest DUI News and Information From DUI Defense Attorneys Across the Country

A Marijuana Breath Testing Device?

Marijuana Bag
Image by Steve Oberman 2012

Breath testing devices are commonly used by police officers in their pursuit to enforce Driving Under the Influence (DUI/DWI/OUI, etc.) laws across the nation. These devices not only detect the presence of ethanol, but also attempt to quantify the amount of alcohol in one’s blood. Every state has adopted a per se limit of .08 percent of alcohol in the person’s blood. This means that if a person has a blood alcohol level (breath tests are also commonly used to determine this) at or above .08%, they are automatically considered to be impaired or under the influence.

DUI arrests and convictions, however, are not always based solely on a person’s consumption of alcohol. For example, the consumption of drugs (legal or illegal) may lead one to be impaired and unfit to operate a motor vehicle.

Recently, several states have legalized recreational marijuana consumption. This raises the question of whether these states will now quantify a certain amount of marijuana in someone’s blood to deem them automatically legally “impaired” and unfit to operate a motor vehicle. A few states have simply outlawed driving with any THC or metabolites in the driver’s blood.

A recent article written by Yoni Heisler highlights a company hoping that such laws proscribing a certain amount of THC or its metabolites are created. Cannabix Technologies is attempting to create a breath testing device that would detect the amount of THC (marijuana metabolite) in the driver’s body by simply blowing into the machine.

The article goes on to quote Barry Knott from a Reuter’s article. Mr. Knott, who is an executive with some experience selling alcohol breathalyzers, states that the first generation marijuana breathalyzers will only be able to say “yes” or “no” regarding the presence of THC in the person’s system. In other words, the device will not provide a “quantitative evidential measure” of the amount of THC in the blood.

In this author’s opinion, this type of marijuana breath testing device will probably not lead to more DUI convictions. The psychoactive chemicals in marijuana only impair a person for 30 – 60 minutes at the most after inhalation. However, the inactive THC metabolites can stay in the body for a prolonged period of time. They are detectible in one’s urine for approximately 28 days and in hair follicles for much longer. With the device only able to provide a positive or negative detection of marijuana metabolites, and not to when or how much THC has been consumed, the device will be of little use in determining if the driver is actually impaired because of the marijuana inhalation. In the end, the device may deter people from smoking marijuana and driving, but will probably not lead to more DUI convictions.

About the Author: Steven Oberman has been licensed in Tennessee since 1980, and successfully defended over 2,500 DUI defendants.  Among the many honors bestowed upon him, Steve served as Dean of the National College for DUI Defense, Inc. (NCDD) and currently serves as chair of the National Association of Criminal Defense Lawyers DUI Committee.  Steve was the first lawyer in Tennessee to be Board Certified as a DUI Defense Specialist by the NCDD.

He is the author of DUI: The Crime & Consequences in Tennessee, updated annually since 1991 (Thomson-West), and co-author with Lawrence Taylor of the national treatise, Drunk Driving Defense, 7th edition (Wolters Kluwer/Aspen).  Steve has served as an adjunct professor at the University of Tennessee Law School since 1993 and has received a number of prestigious awards for his faculty contributions.  He is a popular international speaker, having spoken at legal seminars in 29 states, the District of Columbia and three foreign countries.

You may contact Steve through his website at or by telephone at (865) 249-7200.

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Steve Oberman

Steve Oberman

Since graduating from the University of Tennessee Law School in 1980, Mr. Oberman has become established as a national authority on the intricacies of DUI defense law. Steve is a former Dean of the National College for DUI Defense, co-author of a national treatise ("Drunk Driving Defense" published by Aspen/Wolters-Kluwer), and author of "DUI: The Crime and Consequences in Tennessee" (published by Thomson-Reuters/West). He has taught thousands of lawyers, judges, and members of the general public about the intricacies of this crime. Steve was selected as a Fulbright Scholar to teach American Criminal Law and American Trial Advocacy at the University of Latvia School of Law in 2019; in 2023 taught for a semester as a visiting professor at Eötvös Loránd University (ELTE) Faculty of Law in Budapest, Hungary; and as a Fulbright Scholar at the University of Ljubljana Faculty of Law in 2024. Steve has also presented at a number of judicial conferences in the United States and Canada as well as for law enforcement agencies, including the Federal Bureau of Investigation and the Czech Republic Police Academy. As a Tennessee DUI attorney, Mr. Oberman has successfully defended over two thousand clients charged with Driving Under the Influence of alcohol and/or drugs. In 2006, Mr. Oberman became the first DUI lawyer in Tennessee to be recognized by the National College for DUI Defense as a Board Certified Specialist in the area of DUI Defense law.

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