You’re driving through West Palm Beach when blue lights flash in your rearview mirror. Maybe you rolled through a stop sign, had a taillight out, or swerved slightly in your lane. The stop feels routine at first, but once the officer approaches, things change. You smoked weed earlier in the day and didn’t think it would matter, but now you realize the smell may still be there. If the officer picks up on it or notices signs like red eyes or slow responses, what started as a minor traffic stop can quickly escalate into a DUI investigation.
If that happens, you may be asked to perform field sobriety exercises or take a breath test. Your mind won’t stop racing as you wonder: Can a breathalyzer detect weed? The answer is no. Breathalyzers only measure alcohol, not marijuana or other drugs.
That doesn’t mean you’re safe from charges. Prosecutors in South Florida aggressively pursue DUI cases involving marijuana, and a DUI conviction can affect your freedom, your driver’s license, and your future. To understand how these cases are prosecuted, it helps to look at how Florida law defines DUI when marijuana is involved.
Under Florida Statutes § 316.193, it is unlawful to drive or be in actual physical control of a vehicle if your normal faculties are impaired by a controlled substance, such as marijuana.
Normal faculties are the abilities you rely on to operate a car safely, including perception, judgment, coordination, and reaction time. Actual physical control means you are in the vehicle and have the capability to operate it even if it is not moving (for example, seated in the driver’s seat with keys accessible).
Unlike alcohol cases, there is no legal THC limit in Florida. Prosecutors often rely on officer observations, field sobriety exercises, and sometimes blood or urine testing rather than a numeric breath reading.
A breathalyzer is designed to measure alcohol by detecting ethanol in your breath. According to the U.S. Department of Transportation, these devices are approved only for evidential breath alcohol testing. They cannot identify marijuana or its active compound, THC.
Because a breathalyzer won’t detect cannabis use, officers investigating suspected marijuana DUIs rely on other evidence. They may:
These methods are far less straightforward than a breath test, which is why Florida DUI lawyers often challenge whether the prosecution can prove impairment beyond a reasonable doubt.
While breathalyzers cannot detect marijuana, researchers are developing new devices that may one day identify THC in breath samples. These technologies are still experimental and not yet used by law enforcement in Florida. However, they could eventually change how DUI cases involving marijuana are investigated.
For now, DUI arrests in Florida still rely on officer observations, field sobriety exercises, and toxicology testing. Because the law in this area may continue to evolve, it’s important to stay informed. You can review official information on Florida’s DUI laws and driver’s license regulations at the Florida Department of Highway Safety and Motor Vehicles (DHSMV).
Until such technologies are adopted, Florida courts continue to apply existing DUI laws. In practice, this means a marijuana DUI carries the same penalties as an alcohol DUI.
Even though a breathalyzer cannot detect weed, the penalties for a marijuana-related DUI are the same as those for alcohol. For a first-time DUI, you may face:
Repeat offenses or aggravated cases (e.g., with a minor or property damage) carry harsher penalties. For example, a second DUI within 5 years carries a mandatory minimum of 10 days in jail and up to 9 months total, with fines of $1,000 to $2,000. DUI with property damage is a first-degree misdemeanor, punishable by up to 1 year in jail. DUI manslaughter under Florida Statutes 316.193 is a second-degree felony, punishable by up to 15 years in prison with a mandatory minimum of 4 years. Because the consequences are so severe, prosecutors work hard to secure convictions in marijuana DUI cases, even without a breath test result to rely on.
When marijuana is involved, prosecutors cannot point to a breath test result the way they can in alcohol cases. Instead, they build their case from several different sources of evidence:
Because this evidence is often subjective and less reliable than a breath test, criminal defense lawyers in Florida focus on exposing gaps and inconsistencies. Showing that toxicology does not prove impairment or that field sobriety tests were administered incorrectly can create reasonable doubt for a jury. Any weaknesses in the state’s case often open the door for effective defenses in court.
Every case is unique, but possible defenses raised by a Florida DUI lawyer include:
Some criminal defense attorneys also move to suppress evidence if tests or statements were obtained unlawfully. Knowing the possible defenses is important, but you also need to act quickly after an arrest to protect yourself.
If you’ve been arrested for driving under the influence of marijuana, the steps you take right away can make a big difference in your case:
Remember, a DUI arrest does not automatically mean a conviction. By taking immediate steps, you give yourself the best chance to protect your driving privileges and build a strong defense in court.
When facing a marijuana-related DUI, you’re dealing with more than just a traffic stop. You’re confronting a criminal case that can affect your record, your freedom, and your ability to drive. Prosecutors will aggressively pursue convictions, but you have the right to defend yourself.
Palm Beach County criminal defense lawyer Ronald S. Chapman has more than 34 years of experience handling DUI defense and other criminal offenses. He personally represents each client, using his legal knowledge to challenge evidence and protect the people he serves.
Call (561) 832-4348 or use the confidential online form to schedule a meeting. If you’re facing DUI charges related to marijuana, put Ron’s 34 years of experience to work protecting your future.
Copyright © 2025. Ronald S. Chapman, P.A. All rights reserved.
The information in this blog post (“post”) is provided for general informational purposes only and may not reflect the current law in your jurisdiction. No information in this post should be construed as legal advice from the individual author or the law firm, nor is it intended to be a substitute for legal counsel on any subject matter. No reader of this post should act or refrain from acting based on any information included in or accessible through this post without seeking the appropriate legal or other professional advice on the particular facts and circumstances at issue from a lawyer licensed in the recipient’s state, country, or other appropriate licensing jurisdiction.
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West Palm Beach, FL 33401
(561) 832-4348
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