DUI Breathalyzer Accuracy

Breath analysis is employed in very many DUI cases to test for blood alcohol concentration. Studies of breath alcohol analysis by scientists have mostly been in agreement with the findings of Dr. Michael Hiastala, Professor of Physiology, Biophysics and Medicine at the University of Washington, which come to the conclusion that breathalyzer accuracy is fundamentally unreliable:

“Breath testing, as currently used, is a very inaccurate method for measuring BAC. Even if the breath testing instrument is working perfectly, physiological variables prevent any reasonable accuracy.  Breath testing for alcohol using a single test method should not be used for scientific, medical or legal purposes where accuracy is important.” [Hiastala, Physiological Errors Associated with Alcohol Breath Testing, 9(6) The Champion 19 (1985).]

Safeguards for Breath Testing

It is believed that courts have reserved DUI convictions because the validity of breathalyzer results are not reliable. Four “safeguards” exist for breath testing according to Dr. Kurt Dubowski, a staunch advocate to strict procedures in order to minimize the many opportunities for error in DUI breath testing. [K. Dubowski, The Technology of Breath-Alcohol Analysis (NIAAA 1991):

  1. A pre-test deprivation-observation period of a minimum of 15 minutes.
  2. Blank tests right before each breath specimen collection step.
  3. Analysis of at least 2 different consecutive breath specimens, collected 2 to 10 minutes apart (different results from repeat analysis may point to the presence of errors like radio frequency interference).
  4. An appropriate control test along with every subject test.

The National Safety Council Committee on Alcohol and Drugs has recommended that a minimum of 2 separate breath samples should be taken and analyzed individually. Further, the tests should be collected at intervals of longer than 2 minutes and under 10 minutes. All results of the tests must be collected and reported.

Breath Analyzing Machines

The most economically practical approach in any DUI investigation is breath analysis. Today, there are a wide variety of different breath analyzing machines used:

  • Intoxilyzer 5000
  • Intoxilyzer 9000
  • BAC DataMaster
  • Intoximeter EC/IR
  • Draeger AlcoTest 7110
  • Portable Draeger AlcoTest 7410

These tools have their own mechanism for determining the alcohol content, known as infrared spectroscopic analysis. This operates on the principle that alcohol vapor caught in a chamber will absorb light waves of a specific frequency when beamed through it. In contrast, the Breathalyzer uses a technique called the “wet chemical” technique.

DUI defense lawyers should be knowledgeable about the many pitfalls of breath analysis relating to a DUI case.  For a more in-depth treatment of many of these issues, visit Taylor & Taylor’s presentations Breathalyzer and Breath Test Analysis” and “Breathalyzer Accuracy.”

We have your best interests at heart…