Criminal Defense Attorney Challenges to the Breath Test in a Washington, D.C. DWI or DUI Case

by Jamison Koehler on December 26, 2009

Over the last couple of weeks, I have covered potential legal challenges along every step of an arrest for driving while intoxicated (DWI), driving under the influence (DUI), or operating while impaired (OWI) in Washington, D.C.


Specifically, I have discussed potential challenges to the police officer’s initial stop of the vehicle and the officer’s decision to ask the driver to step out of the car. I have dealt with potential challenges to each of the three tests included in the standardized field sobriety test (SFST) used in D.C.:  the horizontal gaze nystagmus test, the walk-and-turn, and the one-leg stand.  I have also covered the definitions of drinking and driving, the statutory limits for blood alcohol content, potential penalties arising from a first or subsequent conviction, and potential diversion programs for first-time offenders.

Today’s entry focuses on what is normally the last phase of the investigation in Washington, D.C.:  the administration of an Intoxilyzer 5000EN breathalyzer test.  The challenges can be used at either a pre-trial motion to suppress the evidence or at trial.

What is the Breathalyzer Test?

Police use three different chemical tests to measure blood alcohol content: the urine test, the blood test, and the breath test.  Blood tests are the most invasive and also the most accurate.  Both blood and urine tests can also be used to measure the content and amount of drugs in a person’s system.

The test used most frequently in Washington, D.C. is a breathalyzer; specifically, the Intoxilyzer 5000EN.  The subject provides a sample breath into a tube.  The Intoxilyzer then uses infrared spectroscopy to determine the chemical contents of that breath based on the way the molecules of the chemicals absorb light.

Challenges to the Breathalyzer Test

As discussed in greater detail in earlier posts, the first way to prevent breath test results from being admitted into evidence against your client is to challenge the legality of the underlying police conduct leading up to the administration of the test.  The Fourth Amendment protects against unreasonable seizures.  If the court finds that the police officer did not have reasonable suspicion or probable cause for any step of the process, beginning with the stop itself, the court should rule any evidence gathered subsequent to that illegal conduct inadmissible.


Another area for potential challenge would be the way the test was administered.  The Intoxilyzer 5000EN is a complicated piece of equipment.  Any mistakes in administering the test could severely compromise the test results.

For example, the presence of alcohol in the subject’s mouth is widely recognized as the leading cause of error in breath testing.  Because the test is supposed to measure the level of ethyl alcohol in the subject’s lungs, the presence of alcohol in the subject’s mouth can lead to a misleadingly high result.  Burping or regurgitating prior to the test will introduce ethyl alcohol into the subject’s mouth, thereby skewing the results.  As a result, the person who administers the test is supposed to keep the subject under continuous observation for at least 20 minutes prior to administering the test.   How realistic is to assume that the tester will not use this time to fill out paperwork or perform routine administrative chores?

In addition, most people have been socialized to hide bodily functions such as burping.  It is therefore possible that the subject could burp or regurgitate or otherwise reintroduce ethyl alcohol from the stomach to the mouth without the police officer being aware of it.  Chewing gum, smoke, dentures, liver or other health problems in the subject can also skew the test results.

Another area for potential challenge would focus on the functioning of the equipment itself.  Again, the Intoxilyzer 5000EN is an expensive and complicated piece of equipment requiring careful calibration and maintenance.  Any failure by the police department to maintain the equipment in proper working order would compromise any test results.  Defense counsel should request maintenance records prior to trial.  Any failure to perform the semi-annual calibration of the equipment, to perform the weekly simulator test and/or to repair the equipment when anomalous results with the simulator are obtained would be grounds for challenge.

Washington and Jefferson

Even assuming the equipment was properly calibrated and administered, defense counsel can still challenge the test results themselves.  For example, while a blood test directly measures blood alcohol content, the breathalyzer serves as a surrogate measure.  The test measures the concentration of ethyl alcohol and ethanol in a person’s breath.  The system then seeks to extrapolate back to what the person’s blood alcohol concentration must be based on that breath sample.

As Peter Gerstenzang of Gerstenzang, O’Hern, Hickey & Gerstenzang has explained it, all breath test equipment assumes that the concentration of alcohol present in the person’s blood equals the concentration of alcohol in 2100 millimeters of air.  As a result, because the limited breath sample needs to be multipled many times in order to approximate alcohol content in the blood, any potential errors in the sampling will be magnified many times in the result.

The Intoxilyzer 5000EN also assumes that the subject has a body temperature of 98.6 degrees Fahrenheit.  However, a person’s body temperature can fluctuate by several degrees over the course of a normal day.  A person’s body temperature can also be affected by other factors, such as fever from an illness.  Any fluctuation could significantly skew the breathalyzer results to show a misleadingly high blood alcohol content.  For example, a rise in temperature of only 2 degrees Fahrenheit could result in a 10% increase in apparent blood alcohol content.

Test results can also be skewed by the subject’s breathing patterns just prior to the sample.  Three deep breaths before the sample breath can reduce test results by 4%.  Holding one’s breath for 15 seconds before exhalation can increase the result by 12% for a minimum exhalation and 6% for a maximum exhalation.

Finally, as with any witness, the credibility of the arresting officer’s testimony can always be challenged.  Some officers have a tendency to exaggerate in their observations of the subject’s conduct.  Observations of staggering and extremely slurred speech, for example, can be juxtaposed with the finding of a relatively low blood alcohol concentration in the subject.  Conversely, tests results suggesting a very high blood alcohol concentration can be compared with observations of a fairly sober-acting defendant.

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