Breathalyzer Errors: How They Work

James Parker
February 16, 2022
Last edited by
Boruch Burnham, JD
February 16, 2023

Being charged with Driving Under the Influence of Alcohol or Drugs (DUI) can result in a whole slew of potentially devastating consequences, including costly fines, the suspension of your driver's license, and even jail time, not to mention potential lasting negative impacts on one’s a person’s driving record. . The main method of determining whether a DUI charge is valid are the results of the breathalyzer test administered by the officer on the scene. These tests can be damning, but they can also return flawed results.

There are three major issues that can arise with a field-administered breathalyzer test that may cause it to give a blood alcohol content (BAC) reading that is higher than the individual’s actual blood levels. These issues are calibration, timing, and rising windows.


Breathalyzers are sophisticated machines. As such, they require the maintenance of a technician to ensure that they are properly calibrated. An incorrectly calibrated breathalyzer can lead to erroneous and inaccurate   BAC test results.  Breathalyzers must be regularly calibrated at regular intervals which may vary based on the model of the device, manufacturer recommendations, and state law.


The timing of when the officer administers the breathalyzer can also impact the readings it gives. As its name implies, a breathalyzer is meant to examine the amount of alcohol on an individual’s  breath. This breath comes from deep in the lungs to be as accurate as possible. However, if the individual has recently drunk alcohol, burped, or vomited, there may be residual alcohol left in the mouth that could lead to  a  higher BAC reading than is accurate. 

Officers must  wait for what is called an “observation period” (which varies by state but is generally  15 to 20 minutes) to confirm that an individual has not performed  any of these actions before they can administer the test. Additionally, if the individual burps or vomits again in the officer’s presence, the count must be restarted. Failing to observe these rules can result in an inaccurate reading.

Rising Window

Finally, there is something known as the rising window. Most individuals who drink alcohol take one to three hours to fully absorb it into their systems. During this time, their BAC will increase steadily despite them not having drunk  any more alcohol. If a breathalyzer test is administered during these windows, the BAC will be elevated even if the individual’s behavior is unaffected.

If you have been charged with a DUI, you can greatly benefit from  an experienced DUI attorney to help you combat the charges. A DUI attorney can challenge the results of your breathalyzer test by identifying errors in its administration or providing alternate explanations for  high BAC reading. 

Additionally, a DUI attorney can cross-examine the administering officer to determine whether or not they are exaggerating or misrepresenting the threat you allegedly demonstrated. The best place to find a DUI attorney is Attorney at Law.

At AAL, our nationwide network of law firms and attorneys allows us to match you with an attorney in your area. Our partners have the resources, legal expertise, and experience to get you the best results possible for your case. 

In addition to a distinguished case record, our partners also excel in client care. At AAL, we understand the stress that being accused of a crime can cause. That’s why our partners will make sure to keep you updated on the progress of your case, settlement options, and the best recourse in their expert opinions.

Don’t wait. Contact AAL today for a free, no-obligation consultation and assert your legal rights.

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