The short answer is no. The machine at the station is built to identify ethanol, which is drinking alcohol, and it reports a breath alcohol concentration. It does not look for THC, and it cannot report a THC level.
That surprises many folks, because the word breathalyzer has come to stand for roadside testing in general. The distinction matters, though, because it changes how a marijuana case is investigated and how it is fought.
Why the Machine Cannot See THC
An evidentiary breath instrument identifies alcohol by shining infrared light through a breath sample and measuring which wavelengths get absorbed. Ethanol absorbs in particular bands, and the instrument’s filters are set to read those bands. The number it prints is the output of that one measurement, converted into a breath alcohol concentration.
THC is a different molecule with different properties, and it is not what the filters are looking for. It is also present in breath in vanishingly small quantities compared with alcohol, which is part of why detecting it in breath at all has been such a difficult engineering problem. The instrument is not failing to find THC. It was never asked to.
The same infrared method does raise a separate question about compounds that absorb in a range near ethanol, and that issue is covered on what besides alcohol can set off a breathalyzer.
What Florida Actually Uses to Test for Cannabis
When an officer suspects cannabis rather than alcohol, the case is usually built from some combination of the following, and each one has a real weakness:
A blood or urine sample. This is the most common route, and it is where the presence question and the impairment question come apart most sharply. See a drug in your blood is not proof of impairment.
A roadside oral fluid swab. A handheld analyzer reads a saliva sample and returns a yes or no on a panel of drugs including cannabis. It is a screening device that answers whether a trace is present right now, and nothing more. See oral fluid testing and the roadside drug swab.
A Drug Recognition Expert evaluation. An officer trained in a twelve-step protocol offers an opinion that a person was impaired by a particular category of drug. See the Drug Recognition Expert.
Florida Has No Legal Limit for THC
This is the single most important thing to understand about a Florida marijuana DUI, and it cuts in the accused person’s favor.
Section 316.193 sets out two per se limits, and both are written in terms of alcohol. One is a blood alcohol level of 0.08 or more grams of alcohol per 100 milliliters of blood. The other is a breath alcohol level of 0.08 or more grams of alcohol per 210 liters of breath. There is no equivalent number for THC anywhere in the statute.
So in an alcohol case the State can win by proving a number. In a cannabis case it cannot, because there is no number to prove. It has to go the other route in the same statute, which requires showing that a person was under the influence of a controlled substance and affected to the extent that their normal faculties were impaired. That is a question about behavior and evidence rather than a threshold, and it is a good deal harder to establish.
Are THC Breathalyzers Coming?
Research groups and device companies have worked for years on breath-based THC detection, and that work is ongoing. As of this writing, no THC breath instrument is approved in Florida for evidentiary use. The approved evidentiary breath instruments under the state’s testing rules are the Intoxilyzer 8000 and the Intoxilyzer 9000, and both measure breath alcohol.
If that ever changes, the questions worth asking will be the same ones that matter for the alcohol instruments now: what the device was validated against, how it is inspected and maintained, what its records show, and whether a positive reading says anything reliable about impairment at the time of driving.
Presence Is Not Impairment
Cannabis does not clear the body the way alcohol does. Alcohol follows a reasonably predictable curve, which is what makes the whole apparatus of breath testing and retrograde estimation possible in the first place. THC and its metabolites can linger far longer than any effect, and for a regular user they can be detectable when the last use was days earlier.
That is why a positive result and an impaired driver are two different findings. A test can establish that something was present. Whether it affected the person’s ability to drive at the moment they were driving is a separate question, and it is the one the State actually has to answer.
What This Means for Your Case
A marijuana DUI is built on softer evidence than an alcohol case, and that is an opportunity rather than a comfort. There is no number carrying the State’s argument, so what is left is an officer’s observations, a chemical result that speaks to presence, and whatever the video shows. Each of those can be examined.
As an ACS-CHAL Forensic Lawyer-Scientist who sits on the National College for DUI Defense National Task Force on alcohol and drug testing devices, I work these cases from the science outward. The full picture is on the drugged driving defense page.
Questions About Breathalyzers and Weed
Does a breathalyzer detect weed?
No. An evidentiary breath instrument is built to identify ethanol, which is drinking alcohol, and it reports a breath alcohol concentration. It does not test for THC and it cannot report a THC level. A person can blow a 0.000 and still be facing a marijuana DUI investigation, because the State proves that kind of case a different way.
Is there a weed breathalyzer?
Not one that Florida uses to prove a case. Research groups and companies have worked on breath devices intended to detect THC, and that work continues, but no THC breath instrument is approved in Florida for evidentiary testing. Florida’s approved evidentiary breath instruments are the Intoxilyzer 8000 and the Intoxilyzer 9000, and both of them measure breath alcohol.
What do police use to test for marijuana in Florida?
Usually a blood or urine sample, sometimes a roadside oral fluid swab, and often the observations of an officer trained as a Drug Recognition Expert. Each of those has its own weaknesses, and none of them measures impairment directly.
Can you get a DUI for marijuana in Florida?
Yes. Section 316.193 covers driving under the influence of any substance controlled under chapter 893 when a person is affected to the extent that their normal faculties are impaired. Cannabis falls inside that. A valid medical marijuana card is not a defense to driving impaired.
Is there a legal THC limit in Florida like the 0.08 for alcohol?
No. The per se limits in section 316.193 are written for a blood alcohol level and a breath alcohol level of 0.08. Florida has no equivalent number for THC. That means the State cannot prove a marijuana DUI by pointing at a threshold. It has to prove your normal faculties were actually impaired, which is a very different burden.
Does a positive THC test mean I was impaired?
No, and this is the heart of these cases. THC and its metabolites can stay detectable long after any effect has passed, particularly for a regular user. A positive result establishes that something was present at some point. It does not establish how much, when, or whether it affected your driving.
More on the charge itself: marijuana and THC DUI, and a real stop where the driver blew a 0.00 and was still investigated.
Related: the main breathalyzer and breath test defense page, how a breathalyzer works, the roadside drug swab, and drugged driving defense.
Charged after a cannabis stop? The evidence in a marijuana DUI is not a number on a printout. It is an officer’s opinion, a lab result about presence, and a video. All three can be examined, and the Drug Recognition Expert protocol is where that examination usually starts.
This page is general information, not legal advice, and it does not create an attorney-client relationship. Driving under the influence in Florida is governed by Fla. Stat. 316.193, and breath testing is governed by Fla. Stat. 316.1932 and 316.1934 and the Florida Administrative Code chapter 11D-8. Procedures and rules change, and every case turns on its own facts. Past results do not guarantee a similar outcome.
