Can Caffeine Adversely Affect a Maryland Breathalyzer Test?

 Posted on July 29, 2025 in Drunk Driving

When we think of substances that could potentially interfere with a breathalyzer test, coffee is hardly the first thing that comes to mind. While coffee does not contain alcohol, and caffeine itself contains no alcohol, it appears that highly caffeinated beverages can possibly skew a breathalyzer test.

If you are facing Maryland DUI charges after consuming energy drinks, excessive amounts of coffee, or other types of stimulants, you should understand how those substances could alter your BAC test. An experienced Anne Arundel County, MD DUI lawyer can examine the evidence, weigh the strength of the state’s case against you, and begin building a solid defense on your behalf.

What is the Role of PBTs and Breathalyzers in Maryland DUI Cases?

A PBT (Preliminary Breath Test, or Portable Breath Test) is a roadside device used by police officers to establish probable cause for an arrest. The results of the PBT are not admissible in court because these devices are generally considered less accurate than breathalyzers due to environmental conditions and less frequent calibration. Refusing a PBT in Maryland has no penalty and does not affect the obligation to take a subsequent breathalyzer test.

The subject must take the breathalyzer test at the station. This test is considered to be much more accurate, although it can have flaws. Refusing to take a breathalyzer test will result in a suspension of the suspect’s driver’s license, regardless of how the DUI case turns out. Breathalyzer test results are admissible in court and often serve as the key piece of evidence that leads to a DUI conviction.

Could Caffeine Impact a Breath Test?

Caffeine itself contains no alcohol, although some "energy" drinks do contain small amounts of ethanol, along with caffeine, sugar, taurine, and mouth-drying agents. Energy drinks that contain both caffeine and ethanol could potentially raise a person’s BAC, perhaps pushing it over the legal limit. However, in most cases, it is the indirect effects of caffeine drinks that can hasten a DUI arrest.

Caffeine is a stimulant that can mask alcohol’s depressant effect, making a person feel less impaired and more alert than he or she actually is. In turn, this could lead to a false sense of security and poor decision-making skills, leading an individual to drive with a BAC that is above the legal limit.

Even before the breathalyzer test results at the station, the police officer must clearly show probable cause for a DUI arrest. If an individual has consumed high doses of caffeine, especially from energy drinks, symptoms like blurry vision, anxiety, dizziness, restlessness, and increased heart rate can mimic symptoms of DUI and be interpreted by law enforcement as signs of intoxication.

Consuming large amounts of caffeine in energy drinks can make a person perform poorly on field sobriety tests, giving the officer even more reason to believe the person is inebriated. Since some energy drinks contain trace amounts of ethanol, if these drinks are consumed shortly before a breathalyzer test, false positive readings are possible.

Can Consumption of Caffeine Be a Defense Against DUI?

While it is rare, there are cases where an attorney may be able to demonstrate that the energy drinks consumed contained trace amounts of ethanol that skewed the breathalyzer results or that the amount of caffeine consumed made it appear as though the suspect was inebriated when he or she was not.

More often, a DUI attorney will argue improper calibration, mouth alcohol contamination, or procedural violations like no reasonable suspicion for the initial stop, or no probable cause for the breathalyzer test. Expert testimony could be necessary for the defense to be persuasive.

Contact a Queen Anne’s County, MD DUI Lawyer

If you are facing DUI charges in Maryland and believe the breathalyzer results were affected by something you drank, do not try to navigate the system on your own. A skilled Annapolis, MD DUI attorney from Henley & Henley, Attorneys at Law is ready to help you through this difficult time, working hard for the best possible outcome. Our two attorneys have more than 50 years of combined legal experience. Call 410-280-0530 to schedule your initial attorney meeting.