In many cases involving charges of driving under the influence (DUI) charges, a major piece of evidence presented by the prosecutor is the result of a breath test. Breath tests are usually performed at the traffic stop using a device commonly referred to as a “breathalyzer.” If a breathalyzer measures your blood alcohol content (BAC) over the legal limit of 0.08 percent, the officer will have probable cause to arrest you. A reading over the legal limit also creates a legal presumption of impairment and satisfies that element of DUI charges for the prosecutor to convict you.

Many people believe that if the prosecutor has a breathalyzer reading over 0.08 percent, they will automatically be convicted of DUI. However, there are many instances in which a breathalyzer result is inaccurate or unreliable. A skilled defense attorney can determine if this may be true in your situation and may argue that breathalyzer results should not be suppressed in your case.


Unlike a blood test, a breathalyzer cannot directly measure the alcohol levels in your blood. Instead, when you blow into the device, it measures the alcohol in the breath from your lungs and uses that measurement to estimate your BAC. There are many errors that can occur involving the device, the officer’s conduct, and more that can lead to unreliability.


There are many reasons why a breath test result may not be accurate, including the following:

  • The officer using the device was not properly trained in roadside breath testing or did not follow the necessary procedures set by the National Highway Traffic Safety Administration (NHTSA).
  • The device used was older. Older devices can read levels of acetone (common in diabetics or dieters) or environmental chemicals as ethyl alcohol, leading to a falsely high result.
  • The device was not properly calibrated.
  • The device was measuring mouth alcohol instead of deep lung alcohol, which can result in a much higher reading. Mouth alcohol can be present due to recent drinking, burping, acid reflux, using breath spray or mouthwash, or similar factors.
  • The test was conducted before the body had absorbed the alcohol, which commonly causes a false positive.
  • Abnormal kidney function or failure can also lead to a falsely high breath test result.

These are only some factors that can cause an unreliable high breathalyzer reading. Your experienced DUI defense lawyer will examine whether any of these circumstances were present in your case and can argue to have any breath test results thrown out. In such cases, if the prosecutor has no other concrete evidence of impairment, they may drop your charges completely.


At Alpert Schreyer, LLC, our criminal defense attorneys know many ways to defend against DUI charges, including challenging chemical test results. The penalties for a Maryland DUI conviction are too steep to risk not having qualified legal representation. Please contact us online or call our office at (866) 444-6363 today to learn more about how we can assist you.